Home Made Bikes

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flag willems
Posted: Mar 6, 2015 at 8:25 Quote
madm3chanic wrote:
willems wrote:
Here is a project i've been working on. Just welded it up today. Can't wait to see how it rides.

Custom frame

by the look of it, it aint gonna ride bad! short travel, pivots in the right spot, nice linkage up there wiv a good rising rate by the look o tings, ticks all the boxes. nice triangle- where'd you get those swoopy tubes?

i take it its a re-made front triangle jobby? the stays and links look to be from some other bike?

Thanks! It has 150mm of travel, built around a 150mm fork.

I work in the bike industry so the tubes are just some parts in the scrap bin that I harvested... Can't say which ones...

Oh, and the deer painting: apparently it my girlfriends family heirloom from the 1800's. hahahaha.
flag madm3chanic
Posted: Mar 6, 2015 at 8:57 Quote
that must be a good lookin scrap bin brother!
flag willems
Posted: Mar 6, 2015 at 9:29 Quote
madm3chanic wrote:
that must be a good lookin scrap bin brother!

I'm sure it would make a few bike enthusiasts go weak at the knees. hahaha
flag joose
Posted: Mar 6, 2015 at 14:35 Quote
Looks like it will ride like a Rocky, your in for a treat my man. Keep us updated on that thing.
flag EuanBisset145
Posted: Mar 7, 2015 at 1:05 Quote
Sweet looking rig! Got a bit of progress for mine, not started making it yet which was partly down to surgery this week.
Anyway all my tubes and bar has arrived.
photo


Also bought an Alfine hub as my gearbox is still quite a while off being ready to build, strange thing is I thought the shifting would be opposite to normal after trying a zerode but on my one it's just standard which is a bonus!

photo

And I figured I might as well show you one of my Cad drawings of the frameset.

photo
flag TreyDownhill
O+
Posted: Mar 7, 2015 at 7:14 Quote
wow. Pretty complex! It makes me confused!
flag EuanBisset145
Posted: Mar 8, 2015 at 1:05 Quote
It's not too complex, just a high single pivot where the swingarm pulls the linkage to compress the shock rather than push as seen on most bikes. It works in a similar way to a gambler if that helps you visualize how it works.
flag junipercycleworx
O+
Posted: Mar 8, 2015 at 6:02 Quote
That design looks really interesting! Did you figure out any of the kinematics?
flag EuanBisset145
Posted: Mar 8, 2015 at 8:28 Quote
Yeah I've worked out all of the kinematics, I've gone through several ideas from a straight single pivot and right now I've settled on this.

I used linkage to check everything I worked out and compare the design to others. It's reasonably progressive but doesn't ramp up excessively, it has 209mm travel with 73mm rearward travel, so I went with 400mm chainstays at static which will still clear the frame and seat with 26 or 650b wheels. Chainstay at sag is just about 438mm.

It does have a bit of brake squat but I think it's still within acceptable levels where the squat is still an advantage although there is the possibility for a floating caliper if I feel it's necessary. Anti squat levels work out at about 60% at 100mm travel so it shouldn't bob excessively but I wanted to make this so it destroys the gnar, so not too worried about the pedalling being 100% efficient.

26" Geometry at static is 400mm chainstays, 430mm reach, 63 degree head angle, 16" seat tube and 348mm (13.7") bb height so nothing crazy really (chainstays do sound a bit wild but it's only to make it not handle like a boat due to the lengthening of the chainstays.

650b geometry is identical apart from the higher bb which is around 361mm(around 14.25").
flag nitzsche
Posted: Mar 12, 2015 at 5:19 Quote
Hi guys ,
Would geting the privee shan bb height 5mm or 10mm up make the geo suitable for 130mm-150mm forks, instead of 140mm-160mm with out major changes in the bike behavior?

Thanks a lot!! tubes just arrived so I have to decide the geometry for the frame!!
flag smalltownboycustoms
Posted: Mar 12, 2015 at 5:36 Quote
nitzsche wrote:
Hi guys ,
Would geting the privee shan bb height 5mm or 10mm up make the geo suitable for 130mm-150mm forks, instead of 140mm-160mm with out major changes in the bike behavior?

Thanks a lot!! tubes just arrived so I have to decide the geometry for the frame!!

As you are making the frame from scratch you shouldn't need to change the BB drop. Its the axle to crown height that you would change. As you will be running less travel, bottomed out your frame will have more ground clearance than the shan bottomed out (someone correct if I am wrong)

Personally I would design the frame around the fork you intend on running at a specific travel not between 130-150mm. That 20mm difference can affect the geo quite alot.

have a play on this and you will see what I mean.
http://www.cotic.co.uk/geek/
flag BungedUP
O+
Posted: Mar 12, 2015 at 21:25 Quote
Not to interrupt the current conversation, but I felt I should post a photo update of the frame that I was working on earlier.

Also, some of you other builders out there might appreciate the dimpling form tool idea. This makes an easy dimpling tool (to protect the side NOT dimpled) which ends up leaving no deformation. With this, you can dimple the inside of a chainstay, and control as many sides as you want. In this case, it controls the outside, top and bottom, such that when the inside is dimpled, the stay doesn't widen out at the top and bottom.
Dimpling tool made from some scrap tubing left over from a fabrication job and Devcon Plastic Steel Epoxy. The epoxy gets slathered in the tube then placed over the chainstay in the opposite the area to be dimpled. The area is covered in plastic wrap ahead of time. The epoxy is left to cure then removed. The plastic wrap comes off easily and the excess epoxy squeezed out can be easily trimmed.

29er hardtail frame I finished Febuary 2015. Short ride on South Willamette Trail.

29er hardtail frame I finished Febuary 2015. Short ride on South Willamette Trail.

29er hardtail frame I finished Febuary 2015. Short ride on South Willamette Trail.

29er hardtail frame I finished Febuary 2015. Short ride on South Willamette Trail.
flag madm3chanic
Posted: Mar 12, 2015 at 21:54 Quote
LOTR nerd, anyone? Xp

hahaha takes one to know one

nice bike tho, good to see it finished off. can you post a pic of the finished "frogs spectacles"?
flag BungedUP
O+
Posted: Mar 12, 2015 at 22:23 Quote
madm3chanic wrote:
LOTR nerd, anyone? Xp

hahaha takes one to know one

nice bike tho, good to see it finished off. can you post a pic of the finished "frogs spectacles"?

Ha! I do like me some LOTR!

Actually, I'm a Norsky, by ancestry, and strong affiliation due to my upbringing. Probably not too many kids outside of Norway grew up hearing about Fridtjof Nansen and Roald Amundsen all the time. I think that's somewhat more typical of people of Scandinavian decent than is typical for most "whites" (whatever the hell that means) - to identify with one's historical roots. The family farm that we derive our last name from (Bungum) is only a short distance from some pretty cool places, such as the Urness stavkyrkje. There are still Bungums that live in Norway as well. Most people with that name are either directly related by blood, or through ownership of the farm. My middle name is Olaf, and I probably would have been named something even more strongly Norwegian if my Dad thought he could have gotten away with it.
flag madm3chanic
Posted: Mar 12, 2015 at 23:59 Quote
dagnamit i thought i was gonna be able to get away with doing some elvish scrawlings on my gravel bike! "one bike to rule them all..." hahaha

 


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