Time to build my own DH frame
- Thread starter ZenkiGarage
- Start date
I'd be interested in seeing some of the other bikes you have built. I want to build a HT at some point in the not too distant future.
I have a custom street trials frame that my buddy made, it fits a Michelin 2.8 and has 14.75" chain stays. I say its possible.
lets see a picture of all that clearance you have...
It's a little higher than that. Like 12.85ish. But yeah, it's a little too low. I'd go for something more like 13.25 at least.
Goatbike worked for some back in the day too.... Definitely unique. I dug it.
So, sure.... I'd love to see this project work.
So, sure.... I'd love to see this project work.
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26"? what size chain ring? pics or it didnt happen, unless maybe your running a 22 tooth or smaller sprocket
Sell your BB idea to some 29er manufacturer.
Nobody has mentioned bearings in cranks yet running on steel studs for the axle.
Will it have sliding drop outs? Make em long enough to fit the inevitable 27.5 DH tyres to fit, this will fix your BB height when you realize all your toes are broken.
Sounds like a great project. You could easily change swingarm to steepen it up and raise BB a touch if/when you work out it's all wrong. My prediction is rear end will get real loose real easy, and try overtake the front, similar to a 24 rear 26 front feeling.
Might aswell try your concept, it is yours after all. I'd just leave room in the design for quick fix mods(shock shuttle, bolt on drop out, 1.5 headtube for angleset etc). Good luck, please post daily updates.
Nobody has mentioned bearings in cranks yet running on steel studs for the axle.
Will it have sliding drop outs? Make em long enough to fit the inevitable 27.5 DH tyres to fit, this will fix your BB height when you realize all your toes are broken.
Sounds like a great project. You could easily change swingarm to steepen it up and raise BB a touch if/when you work out it's all wrong. My prediction is rear end will get real loose real easy, and try overtake the front, similar to a 24 rear 26 front feeling.
Might aswell try your concept, it is yours after all. I'd just leave room in the design for quick fix mods(shock shuttle, bolt on drop out, 1.5 headtube for angleset etc). Good luck, please post daily updates.
A 15" CS is doable. It's not like a hardtail were you need to fit the chainstay in there. With the high pivot, it can be done. I think it will be too short for good handling though. Bikes, like all vehicles, perform best with 50/50 weight distribution. To short of a rear and you have to shorten the front which gives you a too short wheelbase. Wheelbase probably has more affect on handling than any other measurement, and it's one that is often never looked at.
Precisely!
The issue with dirt jumpers running short rear ends is that you've got to have clearance for a tire and a sprocket in the same area. With a high-pivot and jack-shaft setup, you move those elements away from each other and open up new space to work in.
Now that I've modified my roscoe, and it rides pretty damn well, havent really been in a rush to do another hardtail. My next frame will be a DH specific hardtailI was hoping you were going to make a hardtail but this sounds good too
I'll have to scan them, they are all hand drafted full size and ½ scale.
Not gonna happen.
Im not using a spanish BB, just the style of bearings being pressed directly into the shell. I will be machining the shell out of solid stock. This way I can have just enough clearance in the middle for the 19mm axle to pass through, then I will turn down the middle, basically making the shell look like an hour glass(for the lack of better words).
Thats pretty close to what Im doing, but with more of a radius, to prevent stress risers.
Definitely dig all of your builds! Was inspiration for sure.
Its only that short completely topped out. at sag it will be just over 16", so while riding the bike it wont be that short.
Yup!
regardless of what the exact details are, it sounds like you've got this pretty well thought out.
ETA on this piece of awesomeness?
Jig should be done tonight(I'll take more pictures). I picked up some 7075 aluminum to machine my swinger out of yesterday. Gotta pick up steel either today or tomorrow. This weekend is a race weekend, first weekend of skibowl open, and father days, so I'll be out ripping all weekend. With that said, I probably wont have much of an update on the actual frame until next week some time.
why did you opt for an alu swingarm and a streel front triangle?
just taking a wild guess here, but he's probably more comfortable manipulating and welding steal, planning on machining lots on the swing arm thus the alu
Yup. I own enough machine tools to machine everything I will need. Also, with aluminum, when you weld it you lose a lot of strength, from losing its temper. It can be re-heat treated but its something i dont wanna deal with right now. Plus, the benefit of steel is its compliance, and I think those benefits are better suited for the main triangle, than in the swinger. I could be all wrong though.
This is a big experiment for me, so if I get it together, and its not how I imagined, I'll do another one. Trial & Error.
You guys know the difference between "Trial and Error" and "Research and Development"?...
Nothing. I just get to charge for "Research and Development" lol.
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interested to see how your "no heat treating" plan works out. what Alu are you going to use?
i'm drawing up a new front triangle to build this summer and 6061 is winning, my buddy can get it heat treated for ~$100 so i'm gonna go for it. i had a 6082 frame that cracked rewelded and it cracked again within the first 10 rides..
i'm drawing up a new front triangle to build this summer and 6061 is winning, my buddy can get it heat treated for ~$100 so i'm gonna go for it. i had a 6082 frame that cracked rewelded and it cracked again within the first 10 rides..
Did you determine if infact using a alu rear will save you a considerable amount of weight? As opposed to creating a complete steel ride?? maybe vacume created carbon swingers is the next stage
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are you using alu tubes for the swingarm? box stock? or going full-german and cnc'ing (sorry, had to throw that one in). I'd be concerned about not heat treating alu.
Also, compliance in terms of what?
Full on German hahaha! Thats funny because its true on multiple levels. Im half German btw. The swinger is gonna be machined from solid 7075, so thats why heat treating wont be necessary.
Not too sure on the weight, It'll probably be close. I prefer machining over welding, so thats a big factor for me as well.
Maybe compliance isnt the correct term to use. As most of you know aluminum is rigid as hell. I prefer the feel of steel.
different strength to weight. i too prefer the feeling of steel. my current DH rig is alu front, steel swingarm, and its the best of both worlds. was just curious your reasoning for doing the opposite.
also, you should etch the phrase "moar shimz" into the swingarm while you're at it
Biggest reason, is the ease of manufacturing for me. Machined rear and welded steel front, will be fastest and easiest for me.
I actually have a buddy that does vinyl and decals and thought about having him make me some rediculous stickers to put on it. "moar shimz" on the swinger and "looks flexy" on the frame lol.
I actually have a buddy that does vinyl and decals and thought about having him make me some rediculous stickers to put on it. "moar shimz" on the swinger and "looks flexy" on the frame lol.
Let me know when you're taking orders. I think my next frame is going to be custom.
depending on how this comes out i think a few people might be in the same boat as you. If it looks nice and goes throught a few stages of refinement i imagine lots of people are going to be stoked
I would have never thought I'd go that route but I was describing what I'd like in a frame to a buddy while going up a lift and he said "I think you're going to need a custom" And I realized if I really want a frame that specific then I might have to get one made.
Waiting to see how this one turns out...
it really is a shame that there isn't more custom full suspension builders out there anymore. I remember in the days of people liking tanks there were lots to find, but hydroforming and acronyms for suspension designs kind of killed that. Hood, Tankass, ect
I was just thinking how there are no/very few custom builders....and how surprising that is. I mean, when you can squeeze a Specialized out of a tube in taiwan and charge over 2.5grand for it, I can't imagine it would cost that much to weld one in a garage somewhere out of 4130. Hell, I now have a connection with a machinist, I'd just have to design the parts and find a welder.
Katipo, purgatory, brooklyn, hood, superco....everybody's gone!
those katipo's were super nice too.... wasn't he a user on here? I really liked his stuff and kind of wish i would have jumped on one a couple of years ago. Dobermann can still do custom steel work and the pricing would be too bad, but you would have to be happy with the pivot placement and aesthetics, which i am not. but if you wanted a simple single pivot with custom geometry, they can do it
Yeah, the katipos were awesome. I messaged him on PB but never got a response, he must have quit. When he started, frames were $650. That's crazy. By the end they climbed to like 1500 I think. Still worth it on a frame you can tweak angles on.
I'm really tempted to try and farm some work out to china. If you hop on aliexpress or whatever, you can pick up a ti hardtail for under $1000 shipped, and they'll customize the geometry to your preferences. I'd love to get them to build a front and rear section...
I'm really tempted to try and farm some work out to china. If you hop on aliexpress or whatever, you can pick up a ti hardtail for under $1000 shipped, and they'll customize the geometry to your preferences. I'd love to get them to build a front and rear section...
for the amount of work needed for a custom FS bike (designs, tolerances, QC, etc), i wouldn't recommend dealing with the far east unless its something you already have experience doing.
Actually, exprezo is pretty darn close to a low volume custom fab.
There was a feller on mtbr who had a custom hardtail done. He told them what he wanted, they drew up a sheet with specs and numbers on it, and he gave them approval. All for under a grand. I assume if you wanted to go full retard and have them fully customize one for you, you'd have to do all the drawrings yourself.
There was a feller on mtbr who had a custom hardtail done. He told them what he wanted, they drew up a sheet with specs and numbers on it, and he gave them approval. All for under a grand. I assume if you wanted to go full retard and have them fully customize one for you, you'd have to do all the drawrings yourself.
dunno if xprexo would do custom... then again, i can't really thing of anything on their frame i would want to change.
re: china, sure a custom hardtail is one thing and is reasonably straight forward. full suspension is a whole different animal coughcoughevilcoughcough
i know, I was one of the loudest crying foul. It would be almost infinitely smarter to work in steel with a local welder, even somebody who didn't know bikes. But this isn't smart, it's the internet.
isn't purgatory still around? wow, check this out: low / slack mid travel bike w/ proprietary drivetrain. rad!
someone that didnt know bikes could build it for you for less than someone that does. Source the tubing, headtube, and bottom bracket yourself, build a jigg. Spec up all the angles. Find a local welder to lay down the bead and cut the tubing for you. And then a local machinist to cut up the links ect... I bet it would cost you less than a stock frame if you did it all this way. a couple hours of welding, a few hours of machining, and the tubing. Your ready to go. I actually talked to a few local guys once about doing this and they would have no problems doing it. when you think about what it takes to build what you want, its nothing difficult at all for a journeyman welder to lay down 10 or so welds on tubing. And it isnt hard for a machinist to do up 4 or so 6" links for you
I had heard that he hung up his torch. That bike is rad though, and really pretty close the what I would want in a frame.
I'd heard the same as well. Which is unfortunate, but not terribly surprising. It was only ever a part time hobby/ endeavor for him.
edit: i remember he had done a SUPER adjustable geo AM bike that used a hammerschmidt alongside his custom 4 speed derailler, which looked awesome, but was a bit heavy for a trail bike. still though.