Home Made Bikes

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Posted: Sep 26, 2020 at 3:35 Quote
laynehip,

Just mount an idler sprocket on one of the three bolts immediately behind the main pivot and use a single chain. I've created a Linkage simulation and everything works out pretty nicely, not to mention it being so much simpler.

If you need more chain wrap on the chaining, use a DH chainguide with an idler behind the chainring. If you need chain retention on the idler, mount a guide under one of the neighbouring screws.


EDIT: I see the problem with this suggestion, regarding chainline. Thought it could be mounted outboard, but looks like it would have to be inboard, which would interfere with the shock mounting hardware. Maybe a more complex inboard mount could still be created that would attach to the same bolts and would clear the shock mount hardware.

Posted: Sep 27, 2020 at 9:02 Quote
laynehip wrote:
Tried to move the chain pivot point up using some skateboard wheels.
Second I pedaled the second wheel's shaft bent so much the chain popped off.

Back to the drawing board again. Although not sure what to do this time.


What is in the big gap at the main pivot between where the chainstay is mounted and the main frame? Is that just a spacer currently? Could you place the roller behind there? maybe use a large cassette cog mounted to a narrowed freehub body to give you chain clearance to the chanistay.

Edit: essentially just making the roller concentric to the main pivot.

Posted: Sep 27, 2020 at 17:44 Quote
Okay, I got it to where it is good enough and I am officially calling this thing done.
Ended up moving the wheel to the main pivot and then beefing the hell out of the second roller to clear the double shock mount.
Sure as hell won't bend now and there is a little chain growth but took it out for a ride and it is waaaay better.
So I am calling it a day on this project.

Not sure how durable the skateboard wheels will be long term. Can see them getting eaten up by the chain. Work well though.


Posted: Sep 27, 2020 at 21:02 Quote
Hot Damn! That looks strange, but I very, very impressed.

Posted: Sep 28, 2020 at 16:25 Quote
Need to see a video of this thing being ridden!

Posted: Sep 29, 2020 at 3:18 Quote
Why do you even need the second roller? Just have the one on the pivot point and call it?

Posted: Sep 29, 2020 at 8:18 Quote
dump wrote:
Need to see a video of this thing being ridden!
One is coming!


bikerboywill wrote:
Why do you even need the second roller? Just have the one on the pivot point and call it?
With just the single pivot it would interfer with the shocks/shock mount. So I need the second roller for the chain to clear everything.

Posted: Sep 30, 2020 at 0:46 Quote
Oh yeah, I see that now. Good work

Posted: Sep 30, 2020 at 2:49 Quote
Well here goes nothing....
Before lockdown I read some posts about making bamboo bikes, and thought I'd give it a go.
I have zero experience in anything woodwork, and I'd even admit my DIY is pretty crude.

It's been a long time in the making, but I've finally got to a stage where its almost ridable....
Stage 1 sanding don don dropouts and bb. Still need to wrap another time on the toptube seatstay joint. Also a few filler gaps needed around the BB wrapping. All in going very well. Fibreglass is a absolute pain though find splinters anywhere skins exposed
Original Geo was this:
Geometry mock up of for my Bamboo DIY bike project. Will it work out..... god knows but I m giving it a go anyway
But has evolved with:
1: ditched the double toptube\seatstays for a more conventional single toptube for knee clearance.
2: Shortened the backend to 435mm
3: Steepened the seatangle to 80deg.

Just sorting out getting it built up with wheels n cranks to do some latteral flex tests before I do final finishing work tidying up all the joints and making it waterpoof (epoxy then 2X laquer).

Everything was done 100% by hand, apart from:
1: Alignment of the jig (had the help of a smart phone and bubble level app)
2: Drilling the holes for the dropout mounts. (hand drill chuck wasn't big enough.)

Jig was a crude setup of 2x4 with tonnes of screws, and 4 screws in the bottom (in each corner) so I could adjust it to completely level it on any floor I was working with it on. (conservatory and garden floors aren't level!)
Donor frame for BB, headtube and seattube was a scott spark that someon had bent in half.
Dropouts were spare Carver ICB 26in dropouts I had in my toolbox.
Dropout mounts are marine grade 10mm ply sheet.
Chainstay\seatstay are 20-25mm bamboo from bs-bamboo.co.uk
Downtube/toptube/seattube are 40-60mm bamboo from brycus.co.uk (don't ever use these people!)
Initial joint bonding\shaping was with JBweld full strength with cornflour as the thickener. (3 packs)
Joint wrapping is with standard orthopedic casting tape (10x3.6m 3in rolls, cut in half before wrapping, and I've still got 3 left now)
Lots of junior hacksaw blades, rubber gloves, lollipop sticks and loads of sandpaper.
And even more splinters, cuts, scrapes.
Total cost probably just over £230 give or take.

Full gallery from the start is here: BambooBike album

So far has taken 6months, half of that was waiting for bamboo to turn up due to lockdown, and juggling not annoying the family and missus too much Wink . (she constantly asks me why I need another bike.)
First order of bamboo took ages, was of shocking quality, and mostly oversized so couldn't use any of it for the rear end. I only just managed to get what I needed for the front out of 6x2.4m poles!
Second order of bamboo was much better, but glad I ordered 10 poles as it gave me a lot to pick the best wall thicknesses and widths from, but it was pretty green. SO... luckily doing it slowly allowed that bamboo to dry out nicely in my conservatory for a few months!
I 100% built my jig backwards, working around the parts that I knew I needed to fit on the bike (cranks, fork, and rear hub) and the geo I wanted. Most people do it from the headtube, axle and BB.
But I left myself a bit of wiggle room to make sure it lined up by taking the frame out of the jig before bonding the dropouts on, and doing that with a wheel in it, so I could better see and avoid alignment issues.

Super happy with how it's turned out so far.
Just can't wait to get it finished and out on the nice muddy winter trails Big Grin .

Would it have been cheaper to buy a frame with similar geo maybe, but that's not the point.
It's to prove you can try, and learn from failing along the way.

Posted: Sep 30, 2020 at 6:54 Quote
Wow. Amazingly good looking for a first. Keep at it.

Posted: Sep 30, 2020 at 7:44 Quote
Looks really good! Why bamboo though? Does it have some property that makes it good for mountain biking? Also, are are you thinking of running it rigid or with a fork

Posted: Sep 30, 2020 at 8:05 Quote
ski-n-bike-da-east wrote:
Looks really good! Why bamboo though? Does it have some property that makes it good for mountain biking? Also, are are you thinking of running it rigid or with a fork
Well it's supposed to be really good strength to weight ratio and good at absorbing vibrations too (kinda steel like steel).
I don't know loads about it tbh, just saw you could do it and wanted to give it a go.

It'll be running a 160mm fork and 27.5 wheels.
Can take it up to 29er with my 27.5 ICB dropouts if I want, but they're on my Carver running 27.5wheels.

Posted: Sep 30, 2020 at 8:22 Quote
scar4me wrote:
ski-n-bike-da-east wrote:
Looks really good! Why bamboo though? Does it have some property that makes it good for mountain biking? Also, are are you thinking of running it rigid or with a fork
Well it's supposed to be really good strength to weight ratio and good at absorbing vibrations too (kinda steel like steel).
I don't know loads about it tbh, just saw you could do it and wanted to give it a go.

It'll be running a 160mm fork and 27.5 wheels.
Can take it up to 29er with my 27.5 ICB dropouts if I want, but they're on my Carver running 27.5wheels.

I cant wait to see it finished! I bet itll be loads of fun. If you dont mind me asking, whats an ICB dropout?

Posted: Sep 30, 2020 at 8:52 Quote
Well done Scar4me, you've done a really good job for a first build. especially managing to 'engineer' a yoke for tire and chainring clearance. Providing the joints and the bamboo itself is stiff you're going to have an amazing bike there! The ride of a well built bamboo mtb is amazingly forgiving and supple, you can just push them harder and faster than any other! really hope it works out

Posted: Sep 30, 2020 at 9:54 Quote
lol misread the fork offset as the HA and thought

"dayum this is about to be the grim donut hardtail edition"

Wonder how that cast wrapping material does when it wants to flex.


 
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