# El Rebeco - short ass 29er hardtail



## MiWi (Jan 1, 2013)

Hi guys.
This is my first real MTB project. The last one was some kind of monstercross / full rigid dropbar 29er hybrid whatever - which made me fall in love with offroad cycling.

I love my Monstercross bike, but I want something to ride more relaxed when it comes to technical and descending terrain.

This is the geometry (some kind of allmountain or whatever, I guess)


















It´s designed for a tapered Epicon (15mm through axle), setup with 5" travel. The rear will get the 2SoulsCycles X12 dropouts.

Because these are my first X12 dropouts, I decided to build a chainstay-mitering jig.
Welded the dropouts to the chainstays (bent from round 4130 tubing 19x0.9mm = 3/4"x0.035)


















Put them in the jig and let the mill do the job.









Worked out well (I´ll add a cross-bracing after the seattube is welded)


















This is a Conti Mountain King 29x2.4









Then I made myself a rollbender with 31.8mm dies.

















curved seattube from 31.8x0.9mm = 1.25x0.035 straight gauge 4130. The radius is smaller than the rearwheel to get a long straight section at the end - so I can run (and drop when needed) a rigid seatpost. Just in case I don´t like the dropper-post I just ordered.









That´s it so far. Next steps will be mitering the main-triangle.

Cheers, Michael


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## pvd (Jan 4, 2006)

Great job on the prints. It shows that you really get it, at least on paper. #2 is supurbe other than referencing drop instead of bb height.

You may be digging a hole with the bent tube. It's really not that important to have 'super duper' short stays on a bike. It's nice, but the bent seat tube creates far more major problems. Since your print doesn't show the bent tube, you won't be getting the seat into the right position. You should update the prints to check.

I don't like bent seat tubes as they don't allow for quality fine adjustement of saddle height without really screwing up riding position. You have to nail it or it sucks.

Your detail and craftsmanship look great.


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## MiWi (Jan 1, 2013)

Thanks for your reply Peter.

I didn´t go for super short. 425 was the way my wheight distribution might be well o.k. Would have been enough space to go for 415mm or something like that but didn´t want that. To short for a 191cm guy imho.

Concerning the seattube angle (the effective (!) seattube angle).
The first 2 sketches only show the geometry for the jig / for straight tubes. 
RattleCAD can´t do curved tubes. That is way I implement my curved tubes via CAD. See the green line for effective angle as shown in the sketches.








(this sketch shows 120mm sag / end of travel to also check the space between frontwheel and downtube)

Made a Dummy-Seatpost / Seattube extension to the length of my exact seat-position.
The jig-cone connected the seattube/the dummy where my saddle will be. So the jig is setup to the effective seattube angle.
In this picture you can see that my jig got an extra long rail for the seattube. This way a can grab/hold a seattube far up high, where my sattle will be lateron.









The longitudinal shift of the saddle-position when lowering is no issue for me. I got a fix riding position which is fixed in a range of +- 2mm on all of my bikes. 
I don´t care for the dropped position when descending. It´s even better that the saddle moves more forward because of the curved seattube. This way it is easyer to work my center of gravity behind the saddle / where I need it.


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## unterhausen (Sep 28, 2008)

is that a homemade radius toolpost I see? Any more pictures of it?


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## MiWi (Jan 1, 2013)

Yes its homemade. (All my tools are homemade.)
I have 2 radius tools. For large radius and for small radius / immersion.
I can make another picture of the immersion radius tool used for the roller dies this evening.
This is the other one / big one, the small one is quite the same but with a continious shaft.









It´s simply just a stainless steel rod running in tight bronze bushings. 
Both use 8mm HSS cutting steels or old 8mm drill ground to a "turning tool".


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## MiWi (Jan 1, 2013)

Made a better picture of the radius turning tool.


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## unterhausen (Sep 28, 2008)

I love it, thanks for the pics.


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## MiWi (Jan 1, 2013)

Most important: The handhold is carbon and the clamp is titan. Everything else doesn´t work. 

(in fact those are relics from when my father broke his pelvis and most of his leg-bones in a motorcycle crash)


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## pvd (Jan 4, 2006)

Very good work. It's nice to see so much quality thought going into the bike well before metal starts getting cut. Looking forward to seeing more.


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## TrailMaker (Sep 16, 2007)

Interesting, eh?

As I learned, and as it occurred to me somewhere early in that journey, it was the process itself that consumed most of the energy and creativity. The bike itself was almost a _fait accompli_.

Quite creative and accomplished you are, Sir. Obviously, possessing a lot of parallel/tangential knowledge. The bike will be marvelous, no doubt!


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## eMcK (Aug 22, 2007)

Pretty amazing stuff so far.

Personally, with stays that short, I'd prefer a slacker head angle (~68), but that is me, not you. Looking forward to seeing the completed bike!


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## MiWi (Jan 1, 2013)

Thanks guys.



> it was the process itself that consumed most of the energy and creativity.


Indeed. Better think twice than cut twice.



> Personally, with stays that short, I'd prefer a slacker head angle (~68), but that is me, not you.


I know, the chainstays and bike is quite short and quite on the steep side.
There are 2 reasons: 
-Love the quaterhorse from 2Souls-Cycles, which has a similar in geometry.
- I spend a lot of time on my other (non offroad) bikes, which are all are very short and very steep. I am used to it and I love it. My Polobikes have 75° hta, 360mm chainstays, 940mm wheelbase. I know this is not offroad and not comparable. But till now my formula was: Look at the common standard and make it a little steeper and a little shorter and it will work out for you.

Time will tell. First time I cycled offroad is just 2 month ago and I´m gettin deeper into it every day. The terrain I ride is gettin heavier also. Won´t be long till I built the next and different MTB for sure. 
(started framebuilding 22 month ago and this is number 8, so the forecast is, it´s less than 3 month till I start number 9  )


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## afwalker (Apr 26, 2012)

I'm liking the plate to the chainstay for chainring and tire clearance. How thick is it? Looks about 1"/25.4mm wide. It came out with good clearance for a 2x10, if that's the first time you tried it, you nailed it!
cheers
andy walker


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## Walt (Jan 23, 2004)

Keep in mind that using plate for chainstay sections often results in a VERY flexy rear end. Depending on your taste, this can be totally fine or totally unacceptable, it just depends on the preferences of the rider. 

In this case there's enough space that the OP could probably have just used a conventional chainstay. 

But all that aside, this is the most impressive DIY tooling post I have seen in a while! Kickass!

-Walt


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## MiWi (Jan 1, 2013)

Thanks for your comments.

Andy: The plate is 1" x 1/4". I printed a pattern from the chainstay-sketch. Worked out better than I expected. 
This is an older template i made, changed it a bit before I made the chainstays.











> Keep in mind that using plate for chainstay sections often results in a VERY flexy rear end.


Not necessary, when build proberly imho. As I said: This will be reinforced with a brazed box-girder for transverse rigidity. There will be only very little plate left unsupported. Made an FEM model and with the X12 and with the reinforcement there is absolutely no differnce in transverse rigidity.
It will look similar to this lateron, but I´ll plan to make a hollow box-girder connecting the plate and the BBS:



















> In this case there's enough space that the OP could probably have just used a conventional chainstay.


No, not with plenty clearance for mud and 2.4 tires. At least not without crimping the hell out of the stays (see those chainstys from Christopher Henry - love his work but those stays scare me). Massive crimping might lead to fatigue problems in 5 or 10 years.

It may seem I´m a wisenheimer, sorry (indeed, I sometimes am :eekster:).
I plan details of my projects a lot, often it keeps my from sleeping, which is a pain. 
I´m a civil engeneer, designing, calculating and doing manufacturing control of huge steel- and composite bridges. So I´m not that ingenuous concerning those stuff.


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## MiWi (Jan 1, 2013)

Not much work done today. 
Swapped the 29er wheels into my monstercrosser this morning and spend most of the day out in the woods. Quite funny to ride around on 29x2.4 tires on the cross bike. (tight as hell, only 2mm around each tire, just for fun today)









The rest of the day I focussed on that 44mm headtube. Man, whe you are used to that 1.1/8 stuff, 44mm is really HUGE. :eekster::eekster:

Made a set of tapers for the jig.









And purging heatsinks for that headtube.


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## Walt (Jan 23, 2004)

Great stuff!

My comment regarding flex comes from personal experience building a lot of bikes of both styles. I have never done an FEA of any of them, so we're coming at it from opposite directions. And as I said, that's pretty subjective so for most people it's not going to matter. Plate type stays are on all kinds of bikes and are working just fine, obviously. Just not my style when IMO it's easier to just use an oval chainstay. 

I regularly do 41cm chainstay 29ers with conventional stays and decent (65-70mm) tire clearance and not *too* much crimping. You could fit your tire with no crimps at all at 42.5 with most drivetrains, though 2x is typically the tightest.

-Walt


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## Walt (Jan 23, 2004)

It's funny, I thought the 44mm head tubes looked huge a few years ago but now they are on every bike I make, practically - 1 1/8 now looks weird to me!

-Walt


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## MiWi (Jan 1, 2013)

> I regularly do 41cm chainstay 29ers with conventional stays and decent (65-70mm) tire clearance and not *too* much crimping. You could fit your tire with no crimps at all at 42.5 with most drivetrains, though 2x is typically the tightest.


Thanks for the information ! I think I´ll try that on one of the next bikes. 
(Though 65-70mm would be to tight for those 2.4 allmountain tires and the mud we got here for most of the year.)
In fact it looked much tighter in the drawings, than it did now in real life. I was surprised how much clearance there is in the end.
And with building the chainstay subassembly first, there ist no real risk. Tack it and put a wheel in it. If it doesn´t fit, do it over... I´ll try that. Thanks



> It's funny, I thought the 44mm head tubes looked huge a few years ago but now they are on every bike I make, practically - 1 1/8 now looks weird to me!


Yes, is all about what you are used to I guess.
I like the massive look of that short and thick headtube. Will be building more bikes with 44mm.


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## Drew Diller (Jan 4, 2010)

That is good news for me Walt and MiWi, I find I can't make a suitably stiff bamboo frame without a massive 2 inch down tube, which makes a 1-1/8 fork look goofy. More of a marketing thing that I'm going to have to deal with in the future.


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## MiWi (Jan 1, 2013)

Main triangle mitering pretty muc done. 









Next stop-> internal cable routing

My plan so far:
All four cables (both derailleurs, rearbrake and dropperpost) will be routed via the toptube. 
2 of them will be routed internally (still have to decide which two), the other two will be routed externally.

Maybe brake and dropperpost internally. The two derailleurs externally with stops (not full length housing). 
Or I route the external lines for full length housing (no stoppers) so I got all the options which 2 to choose for the external routes.

Any suggestions ?


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## TrailMaker (Sep 16, 2007)

Hey;

If you are running two outside, I'd make it derailleur cables, since they need the most servicing. If you use full length housing, you even eliminate a lot of that.


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## MiWi (Jan 1, 2013)

> If you are running two outside, I'd make it derailleur cables, since they need the most servicing.


Good tip ! Thanks.



> If you use full length housing, you even eliminate a lot of that.


Chose that way with my Monstercrosser and in fact they need very little service. 
My only disconcern is the look. Telling from pictures I´d say thin inner wirer (with stops) under the toptube is more unobtrusive than thicker full length housing. 
Hmm, less servicing or better look....got some time left to think about that.


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## Feldybikes (Feb 17, 2004)

I'm not sure why you would bother running 2 cables internally and 2 externally. Do you think there's not enough room? If you ran the derailluer cables externally on the downtube it would make sense to me, since having the top tube clean for shouldering the bike occasionally can be nice. But I don't understand your motivation. I wouldn't mention this except you solicited input (though realize I'm not quite answering your question).

Also, while I do agree with Trailmaker's suggestion given the circumstances--and if everything is mechanical-- I'd reconsider if your brake and/or dropper is going to be hydraulic. Just seems like a PITA to rebleed (though not undoable).


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## MiWi (Jan 1, 2013)

Thanks for the input.
Shouldering is a thing to consider. Maybe not as much as with my cyclocross, but you never know....

Brake is hydraulic, dropperpost mechanic.
Bleeding is no problem for me. Did that on all my motorcycles regularly. The one-way bleeding from shimano makes it supereasy. Did that on my polobikes and had no problems.

Reason for all 4 routings via toptube: 
Don´t want anything under my BBS (touchown on rocks, dirt/mud etc.).
Beside that: Brake is upon seatstay, so routing with a slope down chainstay looks weird. Rear derailleur cable is also heading into the seatstay direction.

Telling from ggogle picture search 80-90% of all allmountain-like hardtails route all cables on the toptube.

Reason for 2 internally, 2 externally:
4 externally on one tube looks way to chaotic for me. 3 would be okay, but 4 is to much for me.
Its a 35mm toptube. 2 internally fits good, 3 is a pita, at least for me. Furthermore I´m not feeling good weakening the tube to much. For me 2 internally is a good compromise (internal reinfocement of the holes will be added).

2 Examples, want it just like that but a little cleaner looking.


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## Eric Malcolm (Dec 18, 2011)

MiWi

Good explaination. You have mentioned Reinforcing the holes in a 35mm TopTube. Should be all good IMO. That's a big TopTube. I'll stir the pot, you could put all of the cables in 35mm, but 2 in and 2 out in sensible.

Eric


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## MiWi (Jan 1, 2013)

Hi Eric.


> You have mentioned Reinforcing the holes in a 35mm TopTube. Should be all good IMO.


Not shure if I understand / translate the context right....You mean reinforcing would probably not be necessary ?



> I'll stir the pot, you could put all of the cables in 35mm


I think I am really clumsy when it comes to internal cable routing. I have seen a lot of guys putting 3 cables in one tube and I think I sometimes saw 4 cables. But it even takes a lot of time for me with 2 brasstubes to align them in a way they got at least 5mm space between them (hate rattling-noises). For the next projects I need to practice on a 35mm mildsteel tube if I am able to get 3 in there. Right now I am just afraid not doing it satisfactorily.

Worked on the internal cable routing yesterday. No external shots yet, its fresh from the soaking and not filed.

Seattube ports (one left, one right) 









Headtube inlets (both left)









Because the inlets are very close and so are the tubes, I connected the tubes with some silverbrazing, too. Knocked on the toptube and I think the internal brass tubes should be quiet / not rattling on the trails.

Michael


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## Eric Malcolm (Dec 18, 2011)

Michael, I do mean reinforcing is necessary. What I see in your pictures is good reinforcing. I am not suggesting that you put all cables into the TT, just that it could be done. It is a very hard and patient task to do, but not impossible. I have used over sized cable to put inside the tubing so I could get the bends with-out kinking the tube. Motorcycle clutch cable or similar that fits inside the tube will do. I have found that the cable tubes don't rattle inside the TopTube as it is all very stiff once silvered in, but maybe I have been lucky so far. Tacking them together if possible seems good. At 35mm, there is more room to do this. I have used 2 in 28.6mm without problems. Sorry, no pictures for you.

Eric


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## MiWi (Jan 1, 2013)

Hi Eric.



> Michael, I do mean reinforcing is necessary.


Ah, thanks.



> I am not suggesting that you put all cables into the TT, just that it could be done.


Yes, got you that way.



> I have used over sized cable to put inside the tubing so I could get the bends with-out kinking the tube. Motorcycle clutch cable or similar that fits inside the tube will do.


That is a good idea ! I´ve made a small bending roll (about 2.5" Diameter) with a 7mm radius for the brass tube. Togehter with soft-anneal of the brass tubes with the torch this worked o.k. but leaves very small ripples.
I tried sticking Tig-Rods in the brasstube, but sometimes it was hard to get them out. Will try the motorcycle clutch cable or something similar, thanks !

Michael


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## wms (Aug 8, 2007)

Very impressive work Michael, and a fun thread to watch! Can't wait to see more progress.


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## MiWi (Jan 1, 2013)

Sometimes you are the hammer, sometimes you are the nail.
Yesterday I´ve been the nail. Need your advice, please.

Welded the mainframe yesterday. Right in the middle the Argonbottle was empty and I connected a new one.
Both bottles were grey with green banderole, didn´t look closely at the label which I should have ! :madman::madman:
It was not Argon but 82%Argon+18% Carbondioxide (for MAG welding).
The cursed gas-supplier gave me the wrong bottle (the bill is on 100% argon).

Noticed something was wrong few seconds after I started the torch (leftover of 100% Argon in the line from the old bottle running for few seconds). 
Switched off the torch, but it was already to late. Already layed a 3-4mm long bead. :sad:
Grinded that bead out and started over with a new Argon bottle.

When welding over the old / grinded out part, there were 2 or 3 very little sparks flying and you could tell the conditions were not absolutely perfect.
I guess the tubes embeded some of that Oxy from the 18% carbondioxide gas.

The bead is not dull or burnt, but also not as nice looking as the other parts.
Somewhat rough surface, not flowed as well as it should have. Touched the surface with a file just slightly and there are no bubbles or anything inside as far as you can tell without destroying the joint.
So not really that bad as far as the eye can tell, but we all know that means nothing with welding. I guess it will be more brittle in that zone than the other beads.
This zone is just 1/8-1/4 inch long, but I´m really displeased with this.

Due to the 2 times putting heat into the joint, the headtube is also slightly shrinked towards the toptube where the bad bead was.
Not much (+0.5mm = 0.02" dent towards the toptube, sidewalls right/left each -0.15mm = 0.006" shrinked narrow, front is o.k.), but usually I don´t get any noteworthy ovalisation.
I can´t straighten it, cause the dent is just where the weld to the toptube is.

So I´m quite annoyed and ask myself what to do now.

I´ll ride that frame and keep in mind, I will have to replace it soon or late. But should I reinforce it now ?

Option 1: Don´t agonize no more, ream it, ride it and look after that weld regularly. The headtube is 44mm with 1.3mm walls, enough left to ream.

Option2: Silver braze a reinforcement ring. Just strengthening the headtube, which will have slightly thinner walls left/right after reaming.
This improves nothing for the headtube/toptube connection.

Option3: Make a reinforcement ring which extrudes down to about 1/3 of the toptube. 
Similar to this:








+ make a plate gusset for the top of the toptube.
3a: weld together gusset and ring before attaching both with silverbrazing to the frame
3b: braze gusset and ring with brass in situ and connect them with a fillet. But this means even more heat in that section.
What I don´t like about option 3, is that I can´t see/inspect the weld after it is hidden under the ring/gusset.

What would you do ?

Michael


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## MiWi (Jan 1, 2013)

I guess I just worried to much.

Spend this morning with alignment of the frame on my milling-machine.
Reaming was absolutely no problem, really easy. 
No that much distortion, as I feared.
(Not perfect, but nothing really to worry about.)

ream it like you stole it....



















Pressed the headset into the frame and put the fork in. 
Used a 1/2" thread rod to put some serious pre-stressing on the bearings.
They are running very nice and smooth.










After the succesful reaming I checked the alignment of the mainframe and the chainstays / the rearwheel. 








Mainframe and rearaxle are spot on. The rearwheel is spot on front / back. But 0.015" of to the right on top and -0.015" off to the left at the bottom. Nothing to worry about, I´ll take care of that when connecting the seatstays. 
Cold setting is not needed or could things just make worse, because 0.015 at the wheel is just about 0.005" dropout height.

Next I´ll work on the chainstay cross-bracing and the seattube strutting.


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## heybrady (May 31, 2009)

Very cool. Love to see the process.


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## MiWi (Jan 1, 2013)

Fresh from the soaking tank.









Done.


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## MiWi (Jan 1, 2013)

Bent the seatstays today.

Followed by another clamping crime. 
Made a quick and dirty "mitering device".










Ugly clamping, but nice result:


















Seatstays still need to be mitered to the dropouts.
They will slide down appr. 1cm to connect behind the upper half of the toptube.

Michael


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## MiWi (Jan 1, 2013)

Far from finished, but good enough for 1week testride near Siena / Tuscani. This thing is really fun to ride.


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## adarn (Aug 11, 2009)

Nice! That looks like a super fun bike!

I like the reaming with the fly cutter. That's fancy.


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## MiWi (Jan 1, 2013)

Rollout...
(the candyred is darker, than it appears in the first picture. its more like dark cherries or wine / not orange)


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## TrailMaker (Sep 16, 2007)

OFF TOPIC;

Shown strictly for accuracy/information. No diss intended, please. 










Adjustable boring head for milling precision holes.










Fly cutter, for milling surface preparation. Boring would not be impossible, but very tricky to set up.
---------------------------------------------------------------------------------------

The bike looks great. If it rides as good as it looks....


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## MiWi (Jan 1, 2013)

> The bike looks great. If it rides as good as it looks....


Thanks. Just did a first testride of 4hrs. Was a lot of fun, love it.



> OFF TOPIC;
> Shown strictly for accuracy/information. No diss intended, please.


Sorry, I don´t really understand where you´re pointing me to.
Did I make a mistake with the setup of that boringhead ?


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## TrailMaker (Sep 16, 2007)

No, Not You, Michael;



adarn said:


> I like the reaming with the fly cutter. That's fancy.


What brand/model of mill do you have, by the way? I'm always interested in the machinery. You obviously are quite accomplished with it, as reaming would be a very exacting cut to pull off on a mill.


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## MiWi (Jan 1, 2013)

Ah, missed that.



> What brand/model of mill do you have, by the way?


It´s a Steinel SH3.5. Which is quite uncommon, the Steinel SH4 is quite similar (has automatic feed) and quite popular.








It´s dimensions and wheight is in the Deckel FP1 class.

It´s a horizontal milling machine, but I also got the vertical milling head.
Quite small, quite stiff, old, a little worn out, but I like I. Good enough for what I need it for.


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## MiWi (Jan 1, 2013)

Reaming was easier, than I feared. Placed an angle plate on the table and aligned it with the spindel (to get a guide for the headtube-axis). Then I clamped the frame to the angle and to the table. Centered the headtube with a lever type dial gauge and reamed the upper bearing seat. 
Flipped the frame over and again clapmed it to the table and the angle (which made sure, both reamings aligned in the same axis). Then centered the lower headtube reaming with the lever type gauge and thats it.

The fresh ground HSS tool did a perfect job on the 4130 headtube. Nice and shiny surface, no chattering.


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## chernichovsky (Mar 11, 2011)

Sweet machine !


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## MiWi (Jan 1, 2013)

This weekend I finished El Rebeko "Evo II".

El Rebeko "Evo I" was my first MTB ever. In the last year my riding style changed / developed quite a lot (got a 7" freeride-bike and a 8" downhill-bike in the stable).
So Evo II got a little change here an there to get more downhill performance. 
(slacker, longer, little more travel, 31.6mm seattube for 150mm dropperpost, more clearance for bigger tires, less standover)

geometry with 30% sag: 
67.8° HTA, 73.9° STA, 425mm chainstays, 466mm reach









































































-X12 axle
-140er Pike RCT3/ 51mm offset 
-150mm kindshock LEV
-Formula T1 180mm/200mm
-1x10 with 11-42 (one up), SLX Shadow plus, RAD cage (OnUp), RF Atlas crank + n/w chainring
-Hope Evo 2 hubs/ Flow Ex rims
-35mm Spank Spike stem / 785mm RF Atlas bar / Hope Headset (DIY anodized in orange)

Rode it for 4 hours yesterday and absolutely love it.


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