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  1. #1
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    Building 2 enduro/cc steel frames

    Good day MTBR,

    Sorta skipping the roll call here... I'm Thierry, been building frames very very part time since 2002 now and I enjoy reading this forum. I think it's a great place where a lot of knowledge is shared and I beleive this is the most awesome thing about this forum. I've been working on a little project for a few days now and I thought this would make a good write-up so here it goes.

    Basically my gf had just gotten into mountain biking, she loves it and I personally just dropped off DH for more of an All-Mountain type of riding. So we talked and came to the conclusion that what we needed was a double suspension enduro/all mountain frame that tends to be more on the cross country side. So a 4ish" x 4ish" upgradeable to 5" in the front if needed.

    So here's what they'll look like :

    Building 2 enduro/cc steel frames-fyah6_zpsef25a488.jpeg


    Here's a 2d of the design followed by the goemetry.

    Building 2 enduro/cc steel frames-fyah2d_zpsf870ad53.jpg
    Name:  Geo_zpsf0d01bd3.jpg
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    This is an all steel frame except for the two sideplates, which are, of course Aluminum.

    Building 2 enduro/cc steel frames-fyah5_zps0ca8e7c6.jpeg

    Tube details :
    HT : Custon CNC'd from 4130, 44mm
    DT : 1-1/2" x .035" 4130
    TT : True Temper HAVRDT 1-1/4" x 9-7-9
    ST : True Temper VERUSSTMAG2 1-3/8" external butt 1.6/0.8
    Cross tube : 1" x .028" 4130
    BB : 1-1/2" x 73mm (paragon)
    Pivot tube : 1-3/4" x .065" 4130
    CS : 5/8" Square x .035" 4130
    SS : 5/8" square x .035"
    Dropouts : paragon 1-1/8 round (GF) 1-1/2 round for 12x142 (mine)

    Building 2 enduro/cc steel frames-fyah7_zps28a87a96.jpeg

    Building 2 enduro/cc steel frames-fyah8_zps7976a401.jpeg

    Here's an exploded view of the pivot assembly :
    Bearings (bottom bracket bearings) in teal
    Spacers in red
    Bearing cups in black
    Axle in grey

    Building 2 enduro/cc steel frames-fyah10_zps7999605e.jpeg

    Here's 2d view :
    Building 2 enduro/cc steel frames-fyahpivotdetail_zpsedec9689.jpg

    Most of the tubes and parts are ordered already, gonna be designing a custom jig to make them here in the next few days. I'm hoping building can begin in 2-3 weeks from now.

    Cheers !

  2. #2
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    Reputation: G-reg's Avatar
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    You should put a little more thought into that whole mess....






















    Just kidding , looks like quite a bit of time was spent here.

    Is the suspension geometry based on an existing design? Where/how are you getting your links made?

    And if you missed this 18Bikes' thread, those look like some steel frames that need a nice tapered HT.....
    Slowly slipping to retrogrouchyness

  3. #3
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    Looks fun - is there enough chainring clearance though?

  4. #4
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    That toptube can no way, no how handle what you want to do with it - you'll be welding your crossbrace through the thin section of the tube. Go for supertherm or straightgauge.

    IMO for aggro riding the .035 downtube won't be able to handle mounting a pivot like that, I would go with something beefier (Supertherm!) or find a way to completely capture the pivot with the tube.

    I would bump up the chainstays in size as well - 5/8" square is not going to be very stiff and will be super heavy. Round tube is your best bet for strength/weight.

    Keep us updated! Looks like a great project.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  5. #5
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    We the people ...

    Quote Originally Posted by G-reg View Post
    You should put a little more thought into that whole mess....

    Just kidding , looks like quite a bit of time was spent here.

    Is the suspension geometry based on an existing design? Where/how are you getting your links made?

    And if you missed this 18Bikes' thread, those look like some steel frames that need a nice tapered HT.....
    I figure I'd try this pivot location since it seem to give a good rear wheel path and didn't cause too much chain growth. I then located the shock accordingly. Single pivots are pretty straightforward. All in all, I think it looks like a lot of single pivot bikes out there. Just wanted to keep it simple and have it to work with the frame geometries I decided to go with (rear wheel clears ST properly without being overly long, able to put a the shock tabs on the DT without interfering, shock clears ST properly... etc..)

    I'm having the links' blanks waterjetted by a subcontractant out of 3/8" alu plate, then it goes onto a second operation on a CNC milling machine. CNCing is done by a good friend of mine.

    Yeah I've seen those tapered headtubes 18 bikes is manufacturing, they look good. The problem I have with a tapered headtube is I just can't seem to figure out a way to make the DT and TT notches other than with a file. So until somebody comes up with a tapered/straight endmill that matches the profile of a tapered headtube, straight 44mm headtube will be... at least for me !

    Thanks !

  6. #6
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    Walt,

    Toptube : Supertherm 1-1/4" x 1-0.7-1, sold.

    Chainstays : 3/4" x .035" , 3/4 x .049" or 7/8"x .035" or a chainstay specific tube, what would you recommend ?

    Pivot tube and DT: I was a little worried there too. I first drew it with another 1-1/2" x .035" tube that wrapped the pivot... then said to myself "Aaaaaaa... it'll be all right" Your comment confirms my worries. I chose a straightgage tube obviously because I'd be welding quite of bit of stuff on it and doing so to the thin section of a butted tube didn't seem too too awesome to me. I'll go back to the dwg board with this.

    Your input is very much appreciated. Thanks.

  7. #7
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    Dr. Welby,

    both gonna be 1x10 with 32 or 34 tooth chainring. Clearance won't be a problem !

  8. #8
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    3/4 x .035 should be enough for the chainstays provided you've worked with this kind of thin wall steel before. The seatstays can be .028" probably, I'd just make them 3/4" as well. 7/8" is probably overkill but if you can make room for your tire/chainrings/etc then you could go for it if you want to.

    The 1.5" Supertherm tube (BMXSTDT03? I can't remember the part number off the top of my head) has really long butts and should allow you to attach the pivot to the 1mm section. I would still try to somehow get yourself some more surface area for the pivot/DT joint if possible - you probably don't need to fully capture it but perching it on top of the tube like that is a recipe for disaster.

    I've done the BB-as pivot and it works great. If you want to go a little smaller on the pivot to make that joint easier to build, think about using some 1" headset bearings instead. Still plenty stiff enough (at least in my experience) and much smaller and easier to deal with.

    Man, I love to see people doing FS bikes here. I learn a ton every time.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  9. #9
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    Quote Originally Posted by TLKD View Post
    Dr. Welby,

    both gonna be 1x10 with 32 or 34 tooth chainring. Clearance won't be a problem !
    Good! I'd hate to have to tell my girlfriend "Uh sweetie, you know that bike I've been building for you for the last six months..."

  10. #10
    pvd
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    Good effort, but it's just a single pivot. Why make the rear end so flimsy, comples, and expensive when you could just weld it together properly?

  11. #11
    WIGGLER
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    Looks good the only thing I would add is gusseting from the pivot to the ST to take advantage of that triangle intersection spreading the load out!!!
    PAYASO 36er.....Live the Circus

  12. #12
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    Your frame looks very similar to an Xprezo frame.

    They use Columbus Zona butted tubes for the rear triangle. Not sure what the exact specs are, but you could likely figure it out.

  13. #13
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    Hey;

    It seems to me that if you did a little rejiggering of things, you could nest that pivot housing in BOTH the DT and ST and alleviate any possible overloading from only using the DT. I also sort of agree with PVD that the rear triangle is potentially needlessly complex with the alloy rocker plates instead of a welded connecting member and longer stays-to-pivot, but with perhaps a different or additional reason. I wondered if 3/8 thickness would give you sufficient lateral stiffness within just the rocker itself?
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
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  14. #14
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    I'll add my agreement with TM on the shifting the pivot if possible to nestle between the ST and DT. I admit that I am more a structure person than a Suspension type, but I see the better design path you've used to the rear axle path being true vertical and in the more complex way of acheiving that goal. The Mono Shock style brings the rear wheel into conflict with the seat tube at full compression, so I see your thinking here.
    This needs a more expert over-view by a more experienced person to comment and I hope someone will on the merits of the lateral stiffness.

    I like what you have put together thus far.

    Eric
    If I don't make an attempt, how will I know if it will work?

  15. #15
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    PVD, TrailMaker, EricM, Todwil

    I gotta agree with you guys. I'll go back to the drawing board and work on the rear triangle for a bit. I'll see if I could also relocate the pivot backwards a few thousands but doing so means I also have to relocate the shock mount, this may interfere with the downtube or seattube...

    I'll keep you posted.

  16. #16
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    Why have the extra tube bisecting the toptube?

    The Santa Cruz Heckler has always been a great riding bike. I'd look at modelling things off the Heckler with your updates to geometry and custom sizing.

  17. #17
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    I'll second that. If you want to build a high single pivot just copy what Santa Cruz has done with whatever geometry tweaks you want.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  18. #18
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    Moving the pivot forward would solve a couple issues. The Santa Cruz pivot is fully in the downtube.


  19. #19
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    A Good Choice;

    When I modeled a FS Fatbike, I decided very early on that a single pivot would be just the ticket for a novice builder, and naturally thought of the Legendary Heckler to model it after. It does not hurt one bit that I happen to have one hanging in the garage either. A good riding bike it definitely is!
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  20. #20
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    $0.02...

    -If you do stick with this general design, I don't see why you wouldn't just use off the shelf seatstays and chainstays rather than 4130.

    -If you want to capture more of the pivot between the ST and DT but not move the pivot, you could offset either or both. And/or use a 1.75" Supertherm DT.

    -I don't see this design as needlessly complex for a home builder. Those Al plates would be much heavier made out of steel and if you were to use tubular steel it would be much more complicated. Also, the pivot location seems to be pretty far back compared to a Heckler, so that might be what he's going for.

  21. #21
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    Good evening fellow builders,

    I can't look at an elevated chainstay bike, so copying the heckler or make something similar that I'm very not crazy about, that I'm gonna ride and have to look at for the next few years isn't a viable option for me.

    What you see down there is take #2 with a unified rear triangle, the machinist in me had a little bit of a hard time letting go the CNC'd sideplate but that's all right since I managed to make one sideplate on the driveside.

    I didn't move the pivot but reinforced the pivot section, added a 1" x .035" on top of the pivot tube and I did reposition the seat tube not in line with the center of the BB (so the notch of the pivot grabs a bit of that tube as well). I understand that this is lots of beads in a pretty small area...

    Not any less complicated than the sideplate option imo but it's all for a better bike I beleive. And I think I rather the look of this one.

    Chainstays are the long 465mm 29er novas, I represented the non-driveside without the bend for the tire clearance... Now I'd just need an advice on how to "unbend" a bent chainstay ! Any advices on that would be much appreciated ! If that can't be done then I'll have to choose another tube for the NDS chainstay.

    Anybody's got a suggestion on the thoughest seatstays out there ? I would like to use the stronger supertherm stuff but they ain't long enough since they're BMX specific. Can't take a call...

    DT will be supertherm as well.

    Building 2 enduro/cc steel frames-unirt1_zps540aef78.jpeg

    Building 2 enduro/cc steel frames-unirt2_zpse0fd423f.jpeg

    Building 2 enduro/cc steel frames-unirt3_zps0a2070d4.jpeg

    Building 2 enduro/cc steel frames-unirt4_zpsf87ba389.jpeg

  22. #22
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    What shock are you planning on using?
    Quote Originally Posted by a stoned guy with a beer in his hand eyeballing your sisters bike
    "i fit my bike to fit me;not for looks...nice did you buy that bike from jc whitney?" Stoner Island 1984

  23. #23
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    Well, this looks interesting.

    Any frame that has the direct link to the rear wheel and BB shell cut away will suffer BB rotation. This can be designed out by using various methods including heavier gauged tubing and/or larger Dia tube, bracing and sleeves. My concern with the original was to do with the bearings taking that load instead with the multi linkage that was to be used. I liked it otherwise. The bracing now used at the pivot will be good. I understand the pivot placement for the travel you are looking for and this in combo will address the bearing load somewhat, but I wonder if you have lost that nice vertical wheel movement. These bikes seem to be hard on pivot movement in a lateral sense.
    You could use a fork blade for that chainstay if the dimensions work out to use one. They are very similar in dimensions and could work for you.

    You are rendering drawings very well, and the proportions are also good. I like the cross tube. 'Sus' bikes are interesting in that they don't follow the 'rules' so much and this makes them innovative. Keep working on it. They call this part the frustration zone, its easy to push the save button and try a new theme. You're moving in the right direction - having a go, building up a design profile, keep up the good work.

    Eric
    If I don't make an attempt, how will I know if it will work?

  24. #24
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    I'd use Deda chain stays. You're making 2 bikes (?) so if you want 1 straight and 1 bent, just mix'n'match 2 pairs!

  25. #25
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    Quote Originally Posted by nogod View Post
    What shock are you planning on using?
    Fox Float CTD.


    Quote Originally Posted by Eric Malcolm View Post
    Well, this looks interesting.

    Any frame that has the direct link to the rear wheel and BB shell cut away will suffer BB rotation. This can be designed out by using various methods including heavier gauged tubing and/or larger Dia tube, bracing and sleeves. My concern with the original was to do with the bearings taking that load instead with the multi linkage that was to be used. I liked it otherwise. The bracing now used at the pivot will be good. I understand the pivot placement for the travel you are looking for and this in combo will address the bearing load somewhat, but I wonder if you have lost that nice vertical wheel movement. These bikes seem to be hard on pivot movement in a lateral sense.
    You could use a fork blade for that chainstay if the dimensions work out to use one. They are very similar in dimensions and could work for you.

    You are rendering drawings very well, and the proportions are also good. I like the cross tube. 'Sus' bikes are interesting in that they don't follow the 'rules' so much and this makes them innovative. Keep working on it. They call this part the frustration zone, its easy to push the save button and try a new theme. You're moving in the right direction - having a go, building up a design profile, keep up the good work.

    Eric
    Thanks for the kind words Eric !

    Fork blades could be a good idea for the Non-Drive side chainstays. Length could still be an issue I think.

    Lateral stiffness and bearing load : worst case scenario if those bearings fail under normal abuse, I'll design new cups that can take a stack of 2 bearing side by side, making them 4 to take the load instead of 2. Lateral stiffness of the rear triangle... I guess a guy can't really do much on this after he has chosen the tubes, notched them and everything is welded...

    Here's a detail view of the pivot location and rear wheel path. This is on mine where the CSL sits at 17.25" at rest. I'm hoping this will feel great and pedal good. A guy never know right 'til he throws a leg over it, eh ! Worst case scenario, if this thing bobs like a mofo, I'll just lock the shock !!!

    Building 2 enduro/cc steel frames-path_zpsf6ee669c.jpg


    Quote Originally Posted by Feldybikes View Post
    I'd use Deda chain stays. You're making 2 bikes (?) so if you want 1 straight and 1 bent, just mix'n'match 2 pairs!
    Yes, making 2. Mix and match is, indeed, a good idea. I just looked at Deda chainstays, they're too short.

    My main problem is that I need 436mm of length (direct measurment) for the NDS chainstay (if those stays are 30mm high) from the disc side dropout to the NDS of the pivot. Add a bend into this tube and 440mm long chainstays become just too short... That's why I drew them images with the 465mm stays which still seem to be my only option... Maybe I could just weld them on outside in and work the bend off the small end...

    Some stuff showed up in the mail today... Now I'm becoming the bottleneck of the project as I must send my tooling order out ASAP !!!

    Building 2 enduro/cc steel frames-img_5766r_zpsd89410c9.jpg

    Out of those parts, the zip-tie cable guides are what caused my jaw to drop. These guys are machining every bit of it and there are noburrs, no nothing to add besides, holy.... Just very impressed by them so far !

    Still looking for inputs on seatstays btw...

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