# Planning to build a Steel Hardtail - Advice and Suggestions Solicited



## Berkley (May 21, 2007)

Hello all, I've been planning to build a frame for a while now and I believe I've done enough research to ask questions without looking foolish.

I'm planning to build a steel all mountain hardtail designed around 650b wheels and a Pike set to 150mm. I want a 44mm head tube, 73mm threaded BB, and 142x12mm rear dropouts. My intent is to build a basic jig out of wood and MDF and tube mitering will be done with hacksaws and files (which I have plenty of). The actual welding will be outsourced to my friend Paul who has built a boatload of bike frames and has a great deal of TIG welding experience.

Here's the geometry and a screenshot of my RattleCAD design. The geometry isn't 100% finalized, but it's close. Not pictured in the RattleCAD file (still working to add this) are the Nova pre-bent downtube and a TT/ST brace.


















Here are my questions:

1. Is the 38mm Nova pre-bent downtube adequate for this design? I weigh 160lbs and I don't ride very hard. 
2. For the seat tube I plan on running straight gauge 31.6mm ID, 34.9mm OD from Aircraft Spruce. Since this will be extremely heavy, I'd like to have it externally relieved so it's effectively externally butted. I was thinking .7 in the middle and .9 at the BB end. Thoughts?
3. You'll notice I don't have chainstay or seatstay tubing listed. My CAD design has the bends and shape just about dialed, but I'm not sure what diameter and thickness to go with for a good balance of strength and ride quality. Suggestions are welcome.

Thanks in advance,

Chris


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## BungedUP (Aug 18, 2003)

Hi Chris,

1) Yes. It's a little flexy, but it should be just fine. 

2) You could do that, but I'm not sure why. That's a prime area to reduce weight in a frame. I'd stick a single butted or double butted tube there instead, personally.

3) 5/8 .028, if not aggressively ridden is good for seat stays. 3/4" x .035" seat stays are great for heavy duty, such as street use. Probably more than what you need. There are lots of CS products, most any MTB CS product that fits your tire/CS length/crank will be fine, unless you are doing crazy stuff. You can make your own CS out of 3/4" .035, but it's wide at the DO end, and seems narrow at the BB end, unless you ovalize it. I personally like a larger diameter at the DO end, when I have the choice. 

Don't worry about sounding dumb. In the even that you do, well, people might just underestimate you, which isn't always a bad thing! I don't think you'll have to worry about sounding dumb though.

BTW - your plan sounds both great, and interesting. Take photos and let us see the progress!

-Peter


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## G-reg (Jan 12, 2004)

What are you doing for rear dropouts? Paragon is the only company I'm aware of that sells off the shelf 142x12 drops.

If using the hooded style  you're going to have to be really precise with alignment and cutting the chainstays. And using a TA on the rear makes it even more of a challenge, and requires it to be even more precise. It's a challenge for experienced folks with lots of Anvil toys, turns out pretty damn cool though.

Using Paragon's Polydrops / Rockers / Sliders would allow much more "slop" in creating the rear end, but introduce other issues. These drops can be a bit flexy because they are long or leave the axle kinda cantilevered out behind the joint. They are also Stainless, needing to be silver brazed in. Or can you TIG SS to Chromo? (Stupid question maybe, but it's outside my wheelhouse)

Nothing that can't be overcome, but think about how attached to the 142x12 you are. If you'll go to a std QR rear you'll save a headache or two, and in reality not give up any stiffness.


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## dr.welby (Jan 6, 2004)

For the seat tube you'd be better off making a short sleeve, like this one from Paragon. If you try to relieve it externally ideally you'd want to centerless grind it.


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## afwalker (Apr 26, 2012)

The 38 prebent will be fine. I'd suggest a nova external butt seat tube because they're on sale! 28.6 EXTERNAL BUTT SEAT TUBE 1.2/0.6/0.9 x 580 :: EXTERNAL BUTT SEAT TUBES :: ROUND TUBES :: MAIN TUBES :: TUBES STEEL :: Nova Cycles Supply Inc.
It will be cheaper,lighter and will weld just fine.
+1 on the ease of use on paragon sliders.
I'm a big fan of the deda 29r chain stays , bringhelli or bike lugs carries them , may be out of stock at bikelugs, BikeLugs.com
Cheers
Andy walker


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## cschaafsma (Nov 17, 2012)

If you want to roll with a 31.6 seat pin (which I would for a dropper post) I would recommend the True Temper VERUSSTMAG / VERUSSTMAG2. They list the seat pin size as a 33.1 on their site which is a typo (just called them and I'm guessing will be fixed soon). It's actually for a 31.6. It's a great tube and plenty strong and you don't have to take the time to turn a seat collar and weld / braze it in. I've used it on a lot of bikes now. Here is a link to the ST.

True Temper 34.9 mm (1.375") Seat Tubes for Bicycle Frame Building : Henry James Custom Made Parts For Bicycle Frame Builders and Bike Enthusiasts

3/4 x .035 wall tubing works well for chain stays and 5/8 x .035 wall works well for seat stays.

Also not sure why you need a bent down tube, just make sure it's walked up the HT enough to allow for the fork crown to spin. Typically not an issue with a slacker HT angle and 27.5in tires. Going with a straight down tube on your first build will simplify things for you.

Have fun!


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## Berkley (May 21, 2007)

Thanks for the advice everyone. You've definitely got me thinking. A lot of choices were inspired by this bike: http://forums.mtbr.com/frame-building/first-frame-650b-hardtail-892236.html

1. This bike will be run exclusively with gears, in a 1x10 or 1x11 setup. Part of the reason I want 142x12 is because I want to future-proof this frame as much as possible.

2. The bent downtube will not only clear the fork, but also look cool. To be perfectly honest, it's more of an aesthetic choice.

3. I will inevitably run a dropper post and a 27.2mm seatpost limits my options (no Reverb, no DOSS). Plus, as I understand it, I would need to manipulate the top tube (31.7mm) in some way to miter it for the 28.6mm seat tube. That's why I'd prefer to go 30.9 or 31.6. I also run a lot of seatpost extension and while I've never had an issue with 27.2, something a little thicker would give me more peace of mind. Reading the spec sheets for the seat tube Collin posted, it does indeed indicate that one end has a 4" butt with a 31.7mm ID.

I'm fairly confident in my ability to jig up the front triangle. The rear triangle intimidates me. Right now I just need to finalize my geometry, order some tubes and get a full size print out of my CAD files. Then I can start making tubing blocks and get to work.


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## Berkley (May 21, 2007)

Much progress has been made in the past two weeks, the large majority of it research and reading.

There was also much woodworking. I made tube blocks. And then I ordered tubes. And lo and behold when I put the tubes in the tube blocks I realized they sucked. So I scrapped them and made new ones that are much more functional. There are enough challenges in this project without muddling along with dysfunctional equipment.



















After agonizing over geometry and taking dozens of measurements off my current bikes I think I have the geometry finalized. I say agonizing because if I don't like the geometry on a stock bike I can blame the manufacturer and move on. If I don't like it on this bike, I'm solely responsible. But I've basically taken the geometry from my existing bikes and ported it over while tweaking the things I don't like.

More pictures soon. I'm waiting on a saw guide to cut the tubes and then I'll print out a full scale sheet and start working on the seat tube/BB miter. Will probably get a scrap frame to practice on first.

The longer write up is on my website: Long Travel Hardtail Frame Building: Design and Concept


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## Berkley (May 21, 2007)

*Front Triangle construction*

It's hard to believe I haven't posted in this thread since June when I've been busy working on my frame almost every day. I've been posting details on my own website, and neglected this thread. Here's the condensed version...

One of the first things I did was make these homemade inserts to hold the bottom bracket. I couldn't find an adequate substitute for the cones I see so many professional builders using, and after consulting machine shops I learned the cost to have them made would exceed my budget. Despite how awkward these look, they work well enough and hold the BB shell very securely.










Next I mitered the seat tube which was no trouble at all.









After that I proceeded on to the top tube/seat tube junction.









Then things got tricky. I did a rough miter on the top tube/head tube junction and then went to work on the curved down tube. I tried to order as much tubing as possible from Henry James because they provide tech sheets with tube dimensions while Nova is rather mum on the specifics. Unfortunately the pre-bent DT is a Nova-only part so I put the calculator down, estimated its placement and then started to cut bit by bit until I had it positioned right. First I finished the compound miter at the bottom bracket and then finished the two head tube miters simultaneously (top tube and down tube).



















All of the mitering was done by hand with hacksaws, dremels, files and emery cloth. They turned out great (confirmed by my welder) and I wasn't surprised because I used feeler gauges to fine tune them as tight as possible. In fact I probably over-obsessed on them but I wanted this backyard build to go as smoothly as possible.

By now I have this: 


















(I actually have the seat stays and chain stays mostly completed too, but I'll save that for another post.)


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## Walt (Jan 23, 2004)

This is awesome! I love it when people just ****ing go to it and build with homemade tools. You are going to LOVE the bike when you're done (even if there are 10 things you want to change for the second round).

-Walt


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## MiWi (Jan 1, 2013)

Nice project !
Love the pictures and the way you go for it.

I absolutely share your thoughts on 142x12 and on the 31.6 seatpost.



> For the seat tube I plan on running straight gauge 31.6mm ID, 34.9mm OD from Aircraft Spruce. Since this will be extremely heavy, I'd like to have it externally relieved so it's effectively externally butted. I was thinking .7 in the middle and .9 at the BB end. Thoughts?


I use exatly that aircraft spruce tube for the seattube of my bikes.
I take a 21cm piece (enough for a 420mm Reverb Stealth), turn it down to 1.1-1.2mm where the TT and CS will be attached and in the area of the TT/ST brace. 
0.9mm inbetween. 
This upper piece is welded to a 31.8*0.9mm tube (which I bend in my rollbender for tire clearance, it´s a 29er)

Dropouts:
What dropout do you use ?
This are the dropouts I use.








2SoulsCycles GmbH & Co.KG - X-12 Ausfallenden, Stahlteile

Keep us updated as the building goes on.

Michael


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## Eric Malcolm (Dec 18, 2011)

Ahh... the wood smoke produced will be great when the heat is applied.

Eric


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## todwil (Feb 1, 2007)

Love the jig, miters look perfect the only way this could be better is that you were doing all this in an 8'x8' shed from home depot!!! Looking good!!


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## Berkley (May 21, 2007)

I didn't go with the straight gauge seat tube after all. After cschaafsma alerted me to the typo on the Henry James website, I went with their 31.6mm seat tube because it was simpler and more affordable. The rear dropouts are the 142x12mm hooded ones from Paragon.

I already did a full write up on my site so I'll mostly let the pictures speak for themselves here. I will say that I picked the Nova Deda chainstays because they 1) resemble the specs on the On One frame I'm riding now, which has a pretty good ride quality and 2) give me the tire/chainring clearance that I need with 425mm stays on 650b wheels. They're 30x16mm, single bend and taper down to 1/2" at the dropout. The seatstays are round S-bend, 3/4" at the seat tube and taper down to 1/2" at the dropout to match the chainstays.

I also just noticed that my photos are pre-chainstay brace, which has since been mitered and bolted down.

*Chainstays*





































*Seatstays*


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