# designing a 3 speed mountain biking hub



## jimhead88 (Aug 3, 2011)

Okay this is going to be a long and somewhat technical post that most people will find an absolute bore fest, you've been warned!

First off, great community here, I've lurked for a loooong time and have read an incredible amount of posts, thanks for all the info guys!

So I have been completely obsessed with designing and building my own 3 speed geared hub for months now, I've spent literally hundreds of hours thinking about this, drawing diagrams, and researching planetary drivetrains. I'm completely serious with machining my own gear hub from scratch. (Don't worry I have the CAD and machining side covered... hopefully)

So I have a couple questions, First, what would be your ideal 3 gears (in gear inches)? I was thinking like a 22-25" super low gear, 48-53" general mountain gearing (this would be direct), and an overdrive around 68-72". The reasons are pretty obvious, I can get up most things with 50" unless it's ridiculously steep and long. And, I am also frustrated when I spin out, so I want something that I can cruise on the roads with. What would your guys's picks be? There is obviously a massive gap between 25" and 50", but do you really need to dial in your cadence while going uphill? Mash or Spin your balls off, make your choice.

So without even a cursory explanation as to why, other than: it's design is simpler, it would be lighter, and more efficient. What do you guys think of having the lowest gear being only accessed by reverse pedaling? i.e. when you shifted from 2 to 1 you would still be "in" 2 (direct drive) however when you back pedal you would magically get 22 gear inches of forward movement. Anyway I tried to keep this as short as I could, let me know what you guys think. And please ask questions if you want, I left pretty much everything about the design out.

Thanks for reading,
-Jim


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## vaultbrad (Oct 17, 2007)

To figure out if you like the idea of reverse pedaling try building yourself a retro-direct drive bike. I love everything about this whole idea. Please pursue this with vigor.


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## jimhead88 (Aug 3, 2011)

I'm glad I got a reply, I thought I was relegated to some crazy person who thinks that reverse pedaling is at all a good idea.

Anyway, glad to see someone is taking interest, my first adventure will be machining a single speed hub. I figure I gotta start somewhere, and I will document this so don't worry. I really would love to make it with a roller clutch, but torque specs on off the shelf roller clutches are cutting it dangerously close at 120 Nm maximum torque, and I'm not about to go down the rabbit hole of making my own roller clutch. For reference rohloff specs 100 Nm but also says that their minimum gear ratio is 2.1; so I could possibly get it to work. Does anyone have any advice about this? My second choice will be machining up essentially knock off DT Swiss star ratchets, because I'm thinking I might make use of that design in my geared hub, and in all actuality it won't be that hard. 

And yes, I will probably cobble together a retro direct bike, and since my schwinn world sport is languishing in the corner of my garage, it seems like a perfect candidate. If the reverse pedaling this turns out to be a bust (I'm not holding my breath), then I have a couple other ideas for how to achieve the balls out low gear, but none of them half as elegant. 

Thanks for the encouragement!


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## Ptor (Jan 29, 2004)

In grad school I had a "kick-back" hub on the Schwinn commuter (before it was stolen -- everything parked outside in Beserkeley gets stolen eventually), but you're talking about pedaling backwards anytime you want to spin your 25 inches? That would seem rough biomechanically, particularly after a lifetime of powering a bike by pedaling forward. Definitely something to try out in some sort of simple mock-up before committing real resources. But that being said, I've long thought that a 3-speed internal hub with the ranges you specified would be awesome, and your picks for the range is spot on (IMHO). This effort will be worth following!


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## jimhead88 (Aug 3, 2011)

Ya, the problem is that with a 50" input, 25 inches is impossible without putting power through two gear assemblies or using some sort of stepped gear, which seems overly complicated for a three speed. Also, any 3 speed with this range requires two entire gear assemblies (rings, planets, and suns), which again is complicated and heavy for a 3 speed. However, driving the sun in reverse, with the planet carrier held stationary (anti-reverse freewheel), gives you your 22" out of an assembly that is also usable as a 70" overdrive. 

Yes, how I would set it up is that in first gear pedaling forward is still your direct gear (50") and reverse pedaling would be 22". Ergonomics is my chief concern, although it's 22 gear inches and personally I would only be in it literally 2% of the time. It's really just an alternative to getting off the bike and walking up, so if it's not biomechanically efficient I really don't care. As long as it doesn't hurt my knees I'm fine. Plus, reports online about retro-direct drivetrains say that they are just as comfortable to pedal, I'm just worried about not being able to clear technical climbs while pedaling backwards, hitting a root while spinning your pedals forward might suck.


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## car bone (Apr 15, 2011)

I have a true precision stealth with a roller clutch /one way bearing. If you search my posts and search for true precision and/or stealth one of the posts will come up that shows the make and model of that component. The one thats in the hub is the second biggest model. 

Also that particular components max torque is dependent on the material thats outside it, basically the thickness of the material you put outside it is what determines the maximum torque noting else really (until it defelects). the specced max torque is without anything at all (from the bearing manufacturer). thicker stock there = more torque can be trasmitted. you have to crack the hub to make it malfunction.

If you look at a true precision hub you will se that there is a thick diameter and a thin one. where the one way bearing is, its thick. really thick.


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## car bone (Apr 15, 2011)

i think its an INA HF3020 inside true precision stealth Drawn cup roller clutches - HF


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## jimhead88 (Aug 3, 2011)

Thanks for the link and the info! I did a bunch of research and never stumbled upon your posts. I didn't realize that they just toss an off the shelf roller clutch into their hubs, I thought they had to have some proprietary roller bearing assembly in there like shimano does, but it makes sense why they wouldn't. I may be over thinking this, perhaps I should just build it with the roller bearings and if I break it, whatever. It just gives me a chance to build another. 

As far as the housing being the limiting factor; I could be wrong, but after reading the design and safety guidelines on the site you linked. It looks like your housing can be as thick as you want, but you can only put so much torque on it until you start making indentations in either the shaft or the drawn cup, which makes sense. I.E. Stiff does not equal Hard in Engineering terms.

All of this is well and good, but true percision trusts their design enough to throw a cassette on there and put it up to the task of 22/36 low gear torque, and still have a 5 year warranty. So we will see. 

I really like the idea of a silent clutch, because the beauty of having a reverse gear is that it can always be freewheeling and all you have to do is reverse pedal to realize that low gearing. However with a ratchet system, always freewheeling means that your hub is always clicking, no matter what. If I utilized silent and near instantaneous freewheels I could essentially make a hub that only had 1 pawl that you could shift up or down to engage your sun gear and give you an over drive gear. Not to mention machining a hub this way would be waaaaay easier. The only real penalty, assuming these clutches are up to the torque, would be weight, and that would be counterbalanced by simplicity of design.

Thanks for the info! I'll be sure to creep around your posts some more, but I think my first step, as I said earlier, is going to be building a single speed hub. I think I am going to test out a roller clutch in it and see if my 6'4" 220 frame can't destroy it.


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## car bone (Apr 15, 2011)

I would go with the biggest one way bearing. The axle in the stealth hub is alu with a pressed on polished steel ring/race where the bearing rolls. I'm guessing its handened steel.

For the hub housing I recommend using stainless steel such as 17-4ph or 17-7 or even something more badass. "stiffer" than alu and hardenable by aging.


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## car bone (Apr 15, 2011)

I think you get get them without the drawn cup too, and make your own "drawn cup" how thick and hard you want.


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## jimhead88 (Aug 3, 2011)

I was planning on mounting in in 6061-T6, I haven't spec'd how thick yet. The problem with the housing being stainless is that, if we're talking about the single speed, the housing is the hub shell. With the 3 speed set-up, the housing would be the planet carrier, which could be stainless, it would just be heavy. I guess I'd rather do aluminum for this reason, but we shall see. I guess, I could always press a sleeve between the shell and the bearing to add rigidity. I'll have to do some calculations to understand what is necessary there. 

The basic idea on the single speed is pretty simple, if I'm doing roller bearing. It's basically the same as the stealth hubs. I'll machine the hub shell out of a solid piece of 6061-t6 on a lathe; same with the driver. A one way roller clutch is press fit into the hub shell, and the driver is essentially something to attach the cog to (I'm thinking disc brake bolt pattern, and getting the cogs via velo-solo or some such) and a shaft that I press an inner bearing race onto (off the shelf bearing race, 52100 Chrome Steel). And then some bearings placed between the driver and the hub shell, and on the axle of course (I am also going to turn the axle myself as well). This is a rough outline of what I am going to do. If anyone wants an in-depth drawing or something, I will be making that up in CATIA over the next couple lunch breaks. 

After I have cut my teeth on the single speed hub, I am going to transfer pretty much every one of these ideas over to the 3 speed, with a ton of additions of course.


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## car bone (Apr 15, 2011)

The tp uses a split ring thats threaded (threads onto axle axially and locks with a small hex bolt radially) as a preaload for the bearings. In the TP the clutch is pressed in or possibly cooled in with LN or dry ice.

Steel is 3 times as "stiff" as alu, and 17-4 about 3-5 times as strong, its a zero sum game there really, but its much harder and will last longer, I mean the "cost" here is not the materials per se, its your time, because this will take lots of time.

also look into Latrobe bg42 steel for races and pretty much all wear parts. its stainless bearing steel, the only real stainless bearing steel designed from the start for that application, much better than 440c. Its a martensitic vim-var stainless hss/tool steel. Instead of the 52100 I mean.
Latrobe Lescalloy® BG42 VIM-VAR High Performance Bearing Steel

For a cog carrier/freehub of some sorts I would use sandvik 12c27 or similar (but not 420hc), its extremely fine grained, low carbon SS, very tough (since its low carbon/low Cr and very fine grained)
Like a SS 4130 kinda. The easiest thing to do is just use the shimano cassette pattern, since then you have unlimited amounts of cogs to try. and its easy to swap cogs.

One product I would like to see is a 3sp crank, like that good german one, Schlumpf Drive, but 3 speeds instead. But If I want to see that product I have a feeling I have to make it myself.


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## jimhead88 (Aug 3, 2011)

Dude... The information you are laying down is awesome... I see your point with the stainless, and I agree that the actual cost of materials is only a small part of this gigantic project, so I might as well build it with the utmost quality in mind. My question is whether or not I actually need the stainless steel housing. You may be right by saying weight wise it's a wash, but machining Al is pretty damn easy. With the plan I have, everything can be put together with an interference fit; the inner bearing surface I spec’d is HRC 60-64 can be pressed onto my driver body. This means I can just turn my Al driver on the lathe, and not worry about precision grinding an inner race. My goal here is making machining and assembly easy, and making a hub that works well. It doesn't have to last multiple life times. We’ll see how this all shakes out though, once the design is finished.

The reason I like the 6 bolt pattern is that it seems more robust for holding a single cog onto your hub, and it lends itself better to an aluminum driver, with shimano splines I would definitely take your advice and make it out of some high quality knife steel. All of the drawbacks associated with the 6 bolt pattern do not really apply to me in this instance, so I am probably just going to go ahead and do it. I can find all the cogs I need in 6 bolt pattern, and changing cogs just takes an allen wrench.

As far as 3 speed crank, I thought about it for a long time, and I couldn't think of anything. It's mainly a packaging issue. A 3 speed bottom bracket is a horse of a different color though. Your main drawback is having to build a frame around it, which depending on how you look at it may not be too much of a hurdle. I actually really like the idea of a 3 speed bottom bracket since you can run whatever you want out back. I've seen things like this but most use a gear box design like you seen in manual transmissions. Although I think you could use an epicyclic gear system.


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## car bone (Apr 15, 2011)

If you want to do a proto quick and dirty i would recommend 6061 alu/4130 steel/52100 (if you can get that easily) and some marine brass (it machines really fast). you will probably have to make at least one hub that turns out not so good, when its finished you will see lots of things you want to change for the next version.

I think I saw a schlumpf drive geared bottom bracket yesterday. On flicker i just wrote schlumpf drive and there it was in a dudes hand, some real chunky bit with splined axles sticking out for crank arms.

Any way good luck with machining the parts.


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## jimhead88 (Aug 3, 2011)

Ya, I guess I had more of a prototype mentality. I don't want it to be a throw away, but I don't want to spend a ton of resources on something that I will probably make improvements to. I'm also keeping in mind upgrading parts down the road. I can build these things quick and dirty, but I can always build more robust housing, or change out my driver if I want. Barring an entire rework of the hub most parts I can come back to later once the proof of concept is done. 

Your suggestions are invaluable btw, I'll definitely keep you posted on how this goes.


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## vaultbrad (Oct 17, 2007)

I love everything about this thread. Great conversation and ideas that are often lacking on MTBR.


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## Drew Diller (Jan 4, 2010)

vaultbrad said:


> I love everything about this thread. Great conversation and ideas that are often lacking on MTBR.


Same here.

I like the way you think OP. I have my own musings about tailored drivetrains, but actually getting them made is pretty difficult. Nice thing is you can avoid irritants or come up with compromises you're actually willing to accept. For instance my experience with the Hammerschmidt crank, I couldn't fathom why they'd put such an anemic cable clamp on an otherwise _tank-like_ unit. The thing was a _beast_, and then, what the sh!t is this little thing?

I'd love having something like a three speed Hammerschmidt that isn't overbearingly sealed like a HS and actually spins smoothly. But getting that "third" (second) planetary gear going makes things complicated.


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## dirtdawg21892 (Jul 20, 2009)

this looks awesome, i'm really interested to see how this turns out. ive always thought that i could ride comfortably with only 3 well spaced ratios like you described (climbing, flat, and descending) internal hubs are great, and i would love to run one if it could stand up to the torque and excessive abuse that it would see on a mountain bike.


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## jimhead88 (Aug 3, 2011)

car bone said:


> For the hub housing I recommend using stainless steel such as 17-4ph or 17-7 or even something more badass. "stiffer" than alu and hardenable by aging.


So a quick update, I think I'm moving away for 6061 any part of the hub, after I did some calculations for the housing, it's just not strong enough, I'd have to make the housing extremely thick to make it work. I think 7075 - t6 will work really well.

Anyway, the design is all but done. I skipped right past the single speed hub, I liked the idea of doing it first, but I really just wanted to get started with the three speed. Do you guys have any interest in seeing the insides of the hub before I build it? I could put up a Youtube video or something like that. I'd love someone else to critique my design before I get carried away with myself.


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## vaultbrad (Oct 17, 2007)

I love seeing sequential build shots. I'd like to see the guts when you get it all together.


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## Drew Diller (Jan 4, 2010)

jimhead88 said:


> Do you guys have any interest in seeing the insides of the hub before I build it? I could put up a Youtube video or something like that. I'd love someone else to critique my design before I get carried away with myself.


Absolutely.


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## car bone (Apr 15, 2011)

jimhead88 said:


> So a quick update, I think I'm moving away for 6061 any part of the hub, after I did some calculations for the housing, it's just not strong enough, I'd have to make the housing extremely thick to make it work. I think 7075 - t6 will work really well.
> 
> Anyway, the design is all but done. I skipped right past the single speed hub, I liked the idea of doing it first, but I really just wanted to get started with the three speed. Do you guys have any interest in seeing the insides of the hub before I build it? I could put up a Youtube video or something like that. I'd love someone else to critique my design before I get carried away with myself.


The 7075 t6 is about twice as strong (yeild) as 6061, but not any stiffer, its about 80GPa or so I guess for both of them. the 7075 will be more "brittle" and prefers to crack instead of bending. however you would need a twice as big load to do that in the first place. I heard 2000 series is good if you are expecting the failure to be from fatigue.

My precious #1 | Flickr - Photo Sharing! read the text there, very cryptic imo, its a hub??


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## vaultbrad (Oct 17, 2007)

That's a schlumpf 2 speed unicycle hub


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## vaultbrad (Oct 17, 2007)

Bump for updates. How goes your progress?


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## jimhead88 (Aug 3, 2011)

It goes well, I've been rediculously busy and have been pretty well unable to do much during my knee surgery (damn you soccer!), but I have been finding time to finish off the design. 

tl;dr I ran in to some design issues, and am sacrificing shifting under load and smoothness of shifting for mechanical simplicity.

I ran into an unforeseen road block when I was dimensioning things out in CATIA. I was planning on doing an internal clutch system on the axle, like you see on Rohloffs and Alfines. However, since my sun and planet gears are close in size I am able to scale everything way down. Which is great for size and weight (all told the hub body will be about 60mm in diameter), except that with a module 1 22t sun gear you really don't have the space for a clutch system inside of the gear itself. Not wanting to scale the whole thing up, I explored some other options.

What I think I am going to end up doing is making the whole sun gear slide from side to side and use a dog clutch system on either side of the sun gear to get my desired power transfer. One side would be gear 1 & 2 (reverse pedal and direct gear). Then when it slides to the other side it will mesh with teeth on the axle giving you overdrive. This dog clutch system is essentially the exact same thing as the gear change on a manual transmission. I'm not a huge fan of the gear itself moving, however it greatly simplifies the internal mechanics so I am probably going to stick with it. This will unfortunately make changing gears under load pretty well impossible, but I haven't quite found another option that I like. The real problem is the space. This design sacrifices smooth shifting under load, for greatly simplified design and size requirements.

This problem kind of encapsulates almost every decision I have made from the start of this project. I am not making it fool proof and I'm potentially sacrificing some ergonomics, but I gain a simple and robust design.


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## vaultbrad (Oct 17, 2007)

Oh, man. I'm loving this. Good on you for going through with it. 

Sorry to hear about your knees. My father in law was a life long marathoner and soccer player and has had both knees and both hips replaced. Moves much better now. 

Thanks for the update. I look forward to seeing more.


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## jimhead88 (Aug 3, 2011)

*Why I'm probably not going to build a 3 speed*

Hey guys, sorry for the long wait between updates. I may have warned earlier, but this is going to be a long drawn out process, and I'm super busy with a bunch of other stuff. Also I'll apologize in advance for writing a small novel&#8230;

Anyway, I finished the design which took me forever, but I am not all that happy with it. The overall design isn't bad, but now that I have seen it all born out in front of me I am thinking I might just scrap the whole idea and go 2 speed kickback shifting design. I don't like it for 2 reasons: A) I'd like to keep the feel of a single speed (clean looks, simplified riding experience). B) A three speed just doesn't offer that many advantages over an eight speed (efficiency, weight, cost).

Here is the issue - as I see it - with designing any 3 speed mtb hub:
Once you have a robust infrastructure to shift gears within a moving hub, there really isn't a reason NOT to add a few more gears. Why make a 3 speed hub that weighs and costs only slightly less than an 8 speed hub? What do you gain by trading off 5 more gears? A little simplicity (not much though), a little weight, and a little cost. It's simply a matter of once you are able to work clutches inside a gear hub from a shifter at the handlebars, adding a gear or two really isn't much of a penalty, and if you add a gear or two you might as well chain them together in some way to create more gear ratios. Next thing you know you have an 8 speed gear hub. From my research, the 3 speed hubs today aren't able to stand up to the abuse of mountain biking, and to build them so that they would be able to, your cost, weight, and efficiency would be approaching that of an 8 speed anyway. Maybe this has already been said somewhere, but it was a novel idea to me.

So at the end of the day, let's just cut that granny gear out, and make us a kick back hub&#8230;. I'm going to put up info about that in a couple minutes, but these are entirely separate ideas, so I figured I would split them up into two posts.

Here is a teaser of my hub that I built in CATIA BTW, not going to go into a full explanation unless you want it, that would take way too long


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## jimhead88 (Aug 3, 2011)

*2 speed kickback*

I've looked at the current market for 2 speed kickbacks, and nothing seems to be built for mountain biking. There is also the option of the Schumpf 2 speed cranks, but it doesn't come in the ranges I want, and it's fricking 700 dollars (what the hell&#8230.

The overall design would be super simple for the 2 speed kick back (I may have said that about the 3 speed, but the realities of design have made me feel otherwise). Essentially, I would have a free hub body that engaged a driver, that driver would be splined and have clutch that would be cam shifted by back pedaling. The clutch would directly engage the hub shell, and then when shifted it would directly engage the planet carrier of a planet assembly.

The other option would be to have 2 roller clutches, 1 for engaging the hubshell directly, and another for engaging the planet carrier. Then all you would need is to be able to lock the sun gear to the axle when you want to get into the higher gear.

I'm leaning toward option 1, mainly because this design is easily transferable to different gearing arrangements. Say that you wanted a direct 60 gi gear, and a 40 gi reduction gear. You could essentially design in whatever gear you wanted to be direct drive, and change that to whatever gear you wanted to be your other gearing. Also, funnily enough you could make it a fixed gear hub too. Although kicking back would involve literally going backwards (or just lifting your rear wheel and backpedaling while stopped).

Anyway I'd imagine the concept would be a lot like this: (with different shifting mechanisms, and well a lot of other differences too)

Kris Holm / Schlumpf Geared Unicycle Hub: How It's Made - YouTube


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## lukeNZ (Dec 13, 2012)

jimhead88 said:


> I've looked at the current market for 2 speed kickbacks, and nothing seems to be built for mountain biking. There is also the option of the Schumpf 2 speed cranks, but it doesn't come in the ranges I want, and it's fricking 700 dollars (what the hell&#8230.
> 
> The overall design would be super simple for the 2 speed kick back (I may have said that about the 3 speed, but the realities of design have made me feel otherwise). Essentially, I would have a free hub body that engaged a driver, that driver would be splined and have clutch that would be cam shifted by back pedaling. The clutch would directly engage the hub shell, and then when shifted it would directly engage the planet carrier of a planet assembly.
> 
> ...


not sure if you've seen IB13: Sturmey Archer introduces new 5 speed hubs for 2014, adds new 2 Speed Disc Hubs in 135mm and 120mm spacings

or Product Specs | Patterson Bike

I've love a reliable 2 speed that would take a mtb beating. The patterson isn't mtb rated and only fits a 68mm bb shell and who knows if the sturmey is strong enough or will be available widely. The idea of keeping the extra weight in the bb area rather than way out back is appealling after riding single speed for a long time


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## jimhead88 (Aug 3, 2011)

Ya, I love the idea of having everything at your bottom bracket but I'm not such a fan of all the crank options. One issue is that the step is gigantic. I'm pretty sure this stems from the necessity to have a larger sun gear. You need your sun gear stationary for closer gear ratios, but you also need to pass your spindle through it, on a hub gear you just have to fix it to your stationary axle. So this means you need to have a large sun, it would follow that you also need to have a large Ring gear to get a gear range more usable for "singlespeed" types. A big ring gear makes mounting your chainring a little more difficult too. None of these are insurmountable issues, but the other problem is that most manufacturers market them as a substitute for a front derailleur, or something to increase the gear range of whatever you have at the back of your bike, not as a stand alone 2 speed. So they design it with a wider range.

Reminder, I am not some expert on this subject and could be completely off base with my conjecture. If I am, please tell me.

To the sturmey archer s2, I'm considering giving that a shot knowing full well that it probably won't be up to the task of mountain biking. I would love to be surprised though. It makes sense that if I am going to build my own kickback, it would be good to get my hands on an existing designs, and see how it could be improved upon. If I buy it, I will give a full on review in the IGH forum for those interested. Even if it is up to the task, the build quality is pretty low, so I will probably still look into building my own, or maybe even making improvements to the existing hub. Now that I say that, it might be kind of cool machining higher quality internals for the sturmey archer kickback before going whole hog and starting my own hub from the ground up. We shall see though.


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## Dan Burkhart (Mar 18, 2014)

The original concept was intriguing, but I was wondering how you planned to transmit drive to a sun gear. Probably not impossible, but in the realm of bicycle gearhubs, the sun gear has always served as the reactionary gear in the planetary geartrain. It was fun to think someone was thinking outside that box.
Dan


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## jimhead88 (Aug 3, 2011)

Dan Burkhart said:


> The original concept was intriguing, but I was wondering how you planned to transmit drive to a sun gear. Probably not impossible, but in the realm of bicycle gearhubs, the sun gear has always served as the reactionary gear in the planetary geartrain. It was fun to think someone was thinking outside that box.
> Dan


First off, let me say I love your videos and am looking forward to your rundown of Alfine 8's hub. In my original design I was planning on having the sun gear coupled to the driver in second gear. If you look at my pictures I posted and didn't explain at all, what I am planning to do is have the sun slide from side to side, on one side the sun would be coupled to to axle giving you an overdrive, and on the other side couple to the driver giving you a "unity" gear. The driver is also coupled to the planet carrier at all times via a roller feewheel clutch. The trick was that you can drive your sun both ways but not your planet carrier. Your planet carrier would have a one way clutch on the axle so that when you drive your sun gear in reverse your planet carrier would freewheel on your driver (which is moving backwards) and get stopped on your axle, essentially fixing it in place. With a stationary planet carrier your planets now become essentially idler gears and your ring gear rotates in the opposite direction of your sun gear at a ratio equal to the number of teeth on the sun divided by the number on your ring gear. In my design it would be 22/50.

I'm short on time right now, but I can post more pictures later. Does this make sense?

I'm still a little luke warm on the design for a few reasons. But mainly with 2 roller clutches it would be really heavy, however I don't want to have pawl and ratchets because your reverse gear is always engaged, so it would be ratcheting away all the time. The advantage of not actively engaging the first gear somehow with your shifter, is that you can always just start pedaling backwards when you get caught with your pants down halfway up a hill.

Finally, the sun gear would be moved back and forth with some sort of bell crank... probably just a shimano bell crank with a friction shifter. Gotta run, hope this helps!


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## Dan Burkhart (Mar 18, 2014)

jimhead88 said:


> First off, let me say I love your videos and am looking forward to your rundown of Alfine 8's hub. In my original design I was planning on having the sun gear coupled to the driver in second gear. If you look at my pictures I posted and didn't explain at all, what I am planning to do is have the sun slide from side to side, on one side the sun would be coupled to to axle giving you an overdrive, and on the other side couple to the driver giving you a "unity" gear. The driver is also coupled to the planet carrier at all times via a roller feewheel clutch. The trick was that you can drive your sun both ways but not your planet carrier. Your planet carrier would have a one way clutch on the axle so that when you drive your sun gear in reverse your planet carrier would freewheel on your driver (which is moving backwards) and get stopped on your axle, essentially fixing it in place. With a stationary planet carrier your planets now become essentially idler gears and your ring gear rotates in the opposite direction of your sun gear at a ratio equal to the number of teeth on the sun divided by the number on your ring gear. In my design it would be 22/50.
> 
> I'm short on time right now, but I can post more pictures later. Does this make sense?
> 
> ...


 Yep, it makes sense. Making the planet carrier the reactionary reverses the direction of the input at the output whichever way it flows.
Speaking strictly for myself, I'm not averse to some ratcheting noise. I consider it mechanical music, but there is no question roller clutches are superior in some ways.


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## tcuguy (Aug 14, 2013)

Make this as silent as you possibly can, no reverse pedalling of any kind, and build a prototype for under $1000 and I will personally partner with you and mass produce this (no joke).

Also make sure it doesn't weigh 4 pounds.

This would fit a tiny market, but one that currently has not much going for it (the market between single speeders and 1xX's). A 1x3 would be a great commuter hub (simply because of weight and price, since less gears could mean less cost)


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## jimhead88 (Aug 3, 2011)

Mechanical music... I like that. I think the reason roller clutches aren't used more is because of their torque density, they just won't be as light as a pawl and ratchet system built of the same quality. I'd also like to be able to play around with building some roller clutches and not relying on buying off the shelf roller clutches... If only I owned my own hub company...

I guess I am not abandoning the idea, I just like the idea of not having any shifting mechanism. I'm a perfectly happy single speeder, until spin out on pavement... By dropping the lowest reverse gear you simplify a lot of the internals. 

You could potentially just make a suuuuper simple hub that worked in the same way I described except just drop the over-drive. This would essentially function the same as any retro direct drive, without all the crazy chains hanging out, it would all be internal. Fix the Planet carrier permanently, and have a rearward facing overrunning clutch on your driver: Forward, freewheel engages the hub shell; backwards, rearward facing freewheel engages the sun/ring (depending on if you wanted to gear up or down). Of course, I was fine with sometimes accessing a bailout gear by pedaling backwards, but having one that I used all the time might be a different story. If I'm going to build a two speed though, i'd rather just add a little complexity and make it a kick-back. Still though, the utter simplicity of a hub like this is nothing to be scoffed at.


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## car bone (Apr 15, 2011)

wait doesn't the internals get to be beefier in a 3speed than more speed? If i was designing a 3speed i would make the internals beefy and indestructable. as opposed to the 8 and 11 speed crapout there. also less moving parts = better life.


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## car bone (Apr 15, 2011)

jimhead88 said:


> Mechanical music... I like that. I think the reason roller clutches aren't used more is because of their torque density, they just won't be as light as a pawl and ratchet system built of the same quality. I'd also like to be able to play around with building some roller clutches and not relying on buying off the shelf roller clutches... If only I owned my own hub company...
> 
> I guess I am not abandoning the idea, I just like the idea of not having any shifting mechanism. I'm a perfectly happy single speeder, until spin out on pavement... By dropping the lowest reverse gear you simplify a lot of the internals.
> 
> You could potentially just make a suuuuper simple hub that worked in the same way I described except just drop the over-drive. This would essentially function the same as any retro direct drive, without all the crazy chains hanging out, it would all be internal. Fix the Planet carrier permanently, and have a rearward facing overrunning clutch on your driver: Forward, freewheel engages the hub shell; backwards, rearward facing freewheel engages the sun/ring (depending on if you wanted to gear up or down). Of course, I was fine with sometimes accessing a bailout gear by pedaling backwards, but having one that I used all the time might be a different story. If I'm going to build a two speed though, i'd rather just add a little complexity and make it a kick-back. Still though, the utter simplicity of a hub like this is nothing to be scoffed at.


I have been on my tp stealth now for over a year. it just works. I'm gonna crack it open now in about a month to see how its holding up. maybe i can post some pics here.

the thing with pawl/ratchet systems is this: they are all ****. the best one is white industries because they use real tool steel correctly hardened. 
for springs you need to use real spring steel otherwise they break quite fast. like 5160 or L6 (at its toughness peak), and possibly 6150. for the ring and pawls you need (very) tough, hard, strong and abrasion resistant steel like cpm 1v and 3v. a2, d2 (well maybe), 52100. etc, tough stuff that gets hard. and no one really makes this.


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## jimhead88 (Aug 3, 2011)

car bone said:


> wait doesn't the internals get to be beefier in a 3speed than more speed? If i was designing a 3speed i would make the internals beefy and indestructable. as opposed to the 8 and 11 speed crapout there. also less moving parts = better life.


Yes.. you do get more space. But from all I have read, rohloff and alfine 8's hold up to the riggers of mountain biking adequately. And if something breaks, from what I have gathered, it's not the gears themselves, it's some freewheel assembly. Dan seems to be very well versed in actual hubs designs and could probably point out the weak spots better than I can. Actually, Dan, what are the weakest spots in most hub designs in your experience? My point that I was trying to make earlier was that most of the designs I have come up with aren't going to have gigantic mechanical advantages over an 8 speed.

I was in a little bit of a cynical mood I guess, and just frustrated that I couldn't make it worlds better than what is out there. I may be missing the point however, in that it's mentally simple as well: Climb, Flats, downhill/pavement.

Lastly I totally agree with you about having a roller clutch. It seems it would totally be worth any extra weight to have it dead silent, and instant engagement. I know people always say weight is a huge deal, but in the grand scheme of things, having something that's relatively heavy but runs smooth and efficiently is a trade off I'm willing to make.


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## Andy R (Nov 26, 2008)

I've been following this thread with interest as I've thought for a long time that a reasonably light three speed (or even two speed) hub would suit my needs 99% of the time.
What I couldn't live with is kickback gear changing - it might be fine for road/non technical off-road but not being able to ratchet to position my cranks and time pedal strokes in technical stuff is something that I couldn't get used to.
Maybe this is just me though, and possibly I've spent too much time on singlespeeds where ratcheting is a basic technique - a riding friend of mine has commented on how much I do this (even on a geared bike), whereas he rarely does.


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## Dan Burkhart (Mar 18, 2014)

jimhead88 said:


> Yes.. you do get more space. But from all I have read, rohloff and alfine 8's hold up to the riggers of mountain biking adequately. And if something breaks, from what I have gathered, it's not the gears themselves, it's some freewheel assembly. Dan seems to be very well versed in actual hubs designs and could probably point out the weak spots better than I can. Actually, Dan, what are the weakest spots in most hub designs in your experience? My point that I was trying to make earlier was that most of the designs I have come up with aren't going to have gigantic mechanical advantages over an 8 speed.
> 
> I was in a little bit of a cynical mood I guess, and just frustrated that I couldn't make it worlds better than what is out there. I may be missing the point however, in that it's mentally simple as well: Climb, Flats, downhill/pavement.
> 
> Lastly I totally agree with you about having a roller clutch. It seems it would totally be worth any extra weight to have it dead silent, and instant engagement. I know people always say weight is a huge deal, but in the grand scheme of things, having something that's relatively heavy but runs smooth and efficiently is a trade off I'm willing to make.


 The weak points vary with hub design. In indicator spindle (hollow axle) type shifting, it's sliding key and locking ball interfaces with sun gears. In the Shimano Nexus, failures tend to be a result of broken input reduction sun gears and shift pawls. Hard torquing on the hub when a shift pawl is not fully extended into the internal splines in a sun gear can be a recipe for failure. This is why accurate shift cable adjustment, and non binding cable is critical, and also why shifting under pedaling torque should be avoided. It might be possible to do, but moving shift pawls in and out of engagement with sun gears without breaking torque puts a great deal of wear on the pawls, and can result in incomplete engagement.


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## bikeny (Feb 26, 2004)

jimhead88 said:


> Yes.. you do get more space. But from all I have read, rohloff and alfine 8's hold up to the riggers of mountain biking adequately. And if something breaks, from what I have gathered, it's not the gears themselves, it's some freewheel assembly. Dan seems to be very well versed in actual hubs designs and could probably point out the weak spots better than I can. Actually, Dan, what are the weakest spots in most hub designs in your experience? My point that I was trying to make earlier was that most of the designs I have come up with aren't going to have gigantic mechanical advantages over an 8 speed.
> 
> I was in a little bit of a cynical mood I guess, and just frustrated that I couldn't make it worlds better than what is out there. I may be missing the point however, in that it's mentally simple as well: Climb, Flats, downhill/pavement.
> 
> Lastly I totally agree with you about having a roller clutch. It seems it would totally be worth any extra weight to have it dead silent, and instant engagement. I know people always say weight is a huge deal, but in the grand scheme of things, having something that's relatively heavy but runs smooth and efficiently is a trade off I'm willing to make.


I am also finding this very interesting, so I will throw my opinion out there as well! First off, there is only one hub currently available that can handle the rigors of real mountain biking, Rohloff. I know people are going to chime in saying they are using an Alfine 8 and it works fine. For many people, it works OK, if you are really careful with shift technique, making sure your shift alignment is good often, don't go below the recommended input ratio, etc. Even if you are careful with the above stuff, it can still break. Also, the recommended low ratio for the Alfine 8 is not low enough for real mountain biking.

So anyway, I would love to see another gearhub that can stand up to real mountain biking, whether it's a 2, 3, 5, 8 speed whatever! Personally, I think a 5 speed hub would be ideal for the kind of riding I do (tight, techy singlestack). I can see the appeal of a super simple 2 speed hub, and would probably get one if it really was robust enough, but I think the market would be significantly bigger for a 5 or 8 speed unit.

Just thinking out loud here: I wonder if it's possible to just beef up an Alfine 8? If what you say is correct about the failure mode, maybe it's just a matter of replacing the fragile bits with higher quality, tougher materials?

I have no idea about the inner workings of these hubs, so just let me know if I am way off base!

Mark


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## Dan Burkhart (Mar 18, 2014)

bikeny said:


> I am also finding this very interesting, so I will throw my opinion out there as well! First off, there is only one hub currently available that can handle the rigors of real mountain biking, Rohloff. I know people are going to chime in saying they are using an Alfine 8 and it works fine. For many people, it works OK, if you are really careful with shift technique, making sure your shift alignment is good often, don't go below the recommended input ratio, etc. Even if you are careful with the above stuff, it can still break. Also, the recommended low ratio for the Alfine 8 is not low enough for real mountain biking.
> 
> So anyway, I would love to see another gearhub that can stand up to real mountain biking, whether it's a 2, 3, 5, 8 speed whatever! Personally, I think a 5 speed hub would be ideal for the kind of riding I do (tight, techy singlestack). I can see the appeal of a super simple 2 speed hub, and would probably get one if it really was robust enough, but I think the market would be significantly bigger for a 5 or 8 speed unit.
> 
> ...


 Another apparent weakness in the Alfine design was the straight cut gears on the input reduction sun and planetary gears. This was addressed in the 11 speed with helical gears. This introduces the end thrust factor which must be dealt with in some manner. I've not explored an 11 speed, so I'm not sure how they engineered that. Probably just with thrust washers, but that introduces another wear factor, so there are no easy answers.


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## jimhead88 (Aug 3, 2011)

> What I couldn't live with is kickback gear changing - it might be fine for road/non technical off-road but not being able to ratchet to position my cranks and time pedal strokes in technical stuff is something that I couldn't get used to.


Ya, that has been a major concern of mine. The basic philosophy (if you can call it that), is that it would be like a single speed, but you could access another gearing if conditions changed. So not as much switching in between while mountain biking, but having an over drive when your not mountain biking. With this in mind, the most optimal system would be to create a mechanism that only shifted once per revolution and would revert back to its starting position when you pedaled forward. Since you would probably have something like a gear ratio of 33-20 (assuming a 29er), this would actually amount to 2/3's of a revolution. The idea being that only when you did a full revolution without ever going in the forward direction would you change gears. Would this solve your problem?

I'm starting to realize that two designs are going to be necessary. 1) a 2 speed kickback that fits into the single speed aesthetic; and 2) a 3-5 speed hub that can take mtb abuse, and no back pedaling.



> The weak points vary with hub design. In indicator spindle (hollow axle) type shifting, it's sliding key and locking ball interfaces with sun gears. In the Shimano Nexus, failures tend to be a result of broken input reduction sun gears and shift pawls. Hard torquing on the hub when a shift pawl is not fully extended into the internal splines in a sun gear can be a recipe for failure. This is why accurate shift cable adjustment, and non binding cable is critical, and also why shifting under pedaling torque should be avoided. It might be possible to do, but moving shift pawls in and out of engagement with sun gears without breaking torque puts a great deal of wear on the pawls, and can result in incomplete engagement.


Love it! I have re-evaluated my 3 speed hub aspirations and am currently working on a clutch system that would basically work like a traditional 3 speed hubs. I do think there might be something here, but it all rests (as you have pointed out), on the gear changing mechanism. My newest (my CAD files are now up to V7) is basically 2 clutches with an always stationary sun, both clutches can engage the carrier and ring gears, one clutch is attached to the hub (output), and one is attached to the driver (input). So 1) drive coupled with ring, output coupled with carrier; 2) both coupled with carrier; 3) drive coupled with carrier, output coupled with ring gear. This basic design sounds simple but that's because everything rests on the clutch, and if it can take the abuse. I'm at work and gotta run, but I will try to get a picture of what I got going on before the end of the day.


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