swingarm linkage design

[stonezone]

So I'm really close to starting my frame but the one thing i haven't worked out yet is how to do the swingarm linkage.

I want to go as simple as possible and copy something like the Oset but want it beefier since i'll be using a 3kw GM. Frame will be 4130chromo, swingarm either the same or aluminum (have a bunch laying around from set swingarm mod). I've seen mtn bike kits available but I'd need something a bit beefier... I was also looking into something like a cr85 swingarm off eBay but that seems a little too beefy and would need to be extended. I've got all the welding tools, friends and materials if needed but just a little guidance.

How are all of you guys going about it? There are so many options and ways to place the bearings I honestly don't know where to start.

Anyhow, thanks for the advice and if you're ever on Oahu beers and trail-guidance is on me!

Aloha,

SZ

 

[efMX Trials Electric Freeride]

i would copy.. oops i mean emulate
the suspension design/ geometry from the ktm freeride, zero fx/mx, or electricmoto blade..
all are single pivot and make room for the electric motor while not affecting suspension under power..

http://endless-sphere.com/forums/viewtopic.php?f=9&t=61327

keep us posted.. aloha

 

[Drunkskunk]

Use a standard bottom bracket shell and bearings, then replace the spindle with a 3/4" or 19mm shaft or bolt.

 

[stonezone]

I love this forum... thanks for the quick responses! Emulate is my word for the week.

so DrunkSkunk, something like this:
http://www.paragonmachineworks.com/cgi-bin/commerce.cgi?preadd=action&key=BB2010

I have a ways to go but most of my parts and plans are coming together, so i'll absolutely do a build thread. I still need to do one for my Oset that I updraded to 24" ... but i'd rather play, and we don't have winters here in Hawaii

Thanks!

SZ

 

[Drunkskunk]

Thats the shell, yeah. you may have to narrow it some depending on your design, but the bearings that thread in there are designed to take all thew torque of your weight while pedaling, they should hold up very well as a pivot point.

 

[stonezone]

2 questions:

1) what about how bottom bracket's tighten to the axel, not the bearing? For example, on a skateboard or bike bearings you use a bearing cup (or whatever it's called). Are you using a similar cup, or spacer so it doesn't lock up when you tighten it?

2) Since I live in Hawaii we have to order everything,( including 4130, yeah, no one has it on the island) and I want to make sure i get the right stock since it's so expensive. What wall thicknesses is everyone using for their frame builds with chromoly? I'm told i can get 3/4 with 1/8" wall or 1" with 1/16th wall... Is that pretty much the standard for what everyone is doing here or is everyone going thinner walls? I'm going to prob use 4130 for frame and swingarm although I might use Alum for the swingarm since i have a good stock piece left over from my Oset swingarm extension.

Thanks again!

 

[John in CR]

i would copy.. oops i mean emulate
the suspension design/ geometry from the ktm freeride, zero fx/mx, or electricmoto blade..
all are single pivot and make room for the electric motor while not affecting suspension under power..

None of those appear to have the motor anchored to the swingarm, and unless the motor is either mounted on the swingarm or in the swingarm pivot with the torque anchored to the swingarm, then pulling on the chain will always affect the suspension. Trying to minimize it with the chain alignment like done with motos will help under power, but will exaggerate the effect during regen braking.

 

[SkyknightJohn]

For Q#1 you might like to check out this bottom bracket cup & bearing set from Staton-inc. : http://www.staton-inc.com/store/pro..._crank_Left_and_RIGHT_hand_threads-847-0.html or some of their freewheel adapters: http://www.staton-inc.com/store/products/5_8_ID_x_1_2_wide_Adaptor_for_freewheel_sprocket-876-0.html this one is right hand threads only, but do a search "FWADP" to see all the options. Lots of cool stuff for the home builder.

As to Q#2, most motorcycle tubular frames are 1-1/8" or 1-1/2" OD x 0.120" wall. Depending on your power levels (I see 3KW) you may want .083 or .065 (1/16") to save some weight. Should be plenty. For example bicycle tubing, (check out Nova Cycle Supply http://www.cycle-frames.com/bicycle-frame-tubing/TUBE-SETS/) A typical main tube is 0.9mm (0.035") at the butted ends and 0.5mm (0.019") in the middle.

Look at Aircraft Spruce for the best selection of 4130, at the best prices I've found. http://www.aircraftspruce.com/menus/me/steel.html They have round, square, rectangular, and streamlined in a variety of sizes & wall thicknesses, as well as plate and bar etc... I've always had good service and fast shipping from them, though I don't know how well it will work for you on the islands.

Best of Luck!

 

[stonezone]

free shipping to hawaii for orders over $500.... i LIKE VERY MUCH SUCESS...

 

[SkyknightJohn]

Your question got me thinking... and so I had to try it. I already had the bearing & cup set, I just added a 5/8" bolt. Probably not the best grade to use or anything, just a cheap one from the hardware store. But then, at 5/8", how tough would it need to be? Finer threads would be nice, and a nylon or other locking nut, too. There are probably bearings in this OD (1-3/8") with a smaller ID, if that would be better or more available.

I searched and searched for bicycle swingarm pivot bolts, and eventually (thanks to the forum) found a handful of Raleigh pivot bolts. Fabricating the cups and such for them was a bit tough with my limited tooling. This method seems much easier and uses a higher quality bearing. It's actually a bearing. I'll likely use this method on future builds.

 

[stonezone]

what size BB is that?

thanks for the pics!

 

[SkyknightJohn]

That's a 73mm from Paragon. It would work just as well with a 68mm, or any other size for that matter, you'd just have to get a longer bolt. Standard BB L/R threads 1.37 x 24tpi.

 

[stonezone]

awesome, i got the 73 coming...