Long tail full suspension bolt-on frame

BarkMau

BarkMau

10 W
Joined
Aug 18, 2012
Messages
98
Location
Boca Raton, FL
Hi, I am looking for some of your invaluable input as I am putting together a long tail, full suspension frame. The main frame is a 26” cromoly and the swing arm is from a 24” steel “wally”. The front wheel will be a 26” while a 24” will fill the rear. Not sure yet which wheel will have the DD hub. The expected wheelbase is 561/2” which is close to what most xtracycles are.
One of the goals of the project is to make a bolt-on solution; which means, no cutting and no welding at least on the main frame. I am confident on the way I linked the shock to the frame (custom plate which bolts on the brake bosses). However, don’t feel the same way about how the bottom bracket attaches to the dropouts. For starters, both sides of the BB have different lengths… It is obviously critical the way the rear swing arm works with the frame and it is for this reason that I would welcome your feedback, links, or any other info that could shed some light.
Cheers!
 

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Love to see more FS Frankebikes. Though the shocks on mine are a joke, it's worked amazingly well for me.

Interesting shock mount bracket. Is that a repurposed caster? If you have not tuned it yet, this is how I did mine. I took the original frame and fork, and put wheels on it. Then I measured the height of the pedal crank from the ground. Then when I put on the rear assembly, I made sure the crank height was identical. This makes sure that you haven't ended up with a funny fork angle. Mine ended up riding perfect, with no funny handling issues.


But I do think you must center that swingarm in the frame. Id take a hacksaw to the long part of the BB, or find a cheap bb that is equal in length to install on the swingarm.

Love your bolt on shock mount. Much nicer that what I did, retaining a large chunk of the second frame.

Once I was happy with the connection, I welded my bb to the frames rear droputs. I didn't like relying on just bolts at that point. You can only do that if the front frame is steel of course.

But if you bolt it, which should work fine really, I'd think that some kind of torque arm like device might be good. What I mean is a plate with a round hole for the bottom brackets "axle" to pass through. This then attaches to the front frame. It's not to prevent rotation like a TA, but just to prevent a complete separation of the two parts of the frame. That way if your bolts slip, you get some chance of stopping and getting off before the rear wheel goes bye bye.

Most of the riding forces just want to make the bb jam into the dropout, but you might still have forces when you jump off a curb or whatever going out of the dropout.
 
"DIY longtail, Could it be this easy?"
http://endless-sphere.com/forums/viewtopic.php?f=1&t=9673

I think Dogman and I are the biggest supporters of full-suspension longtails around here. He rides his often, and mine has been dis-assembled since I moved to another state (only have a one-car garage right now).

While mine was running, I loved it. I had it adjusted so that my feet were flat on the ground when I was at a stop. With fat tires it ran like a dream floating on a cloud.

Using a wheel bracket as the shock-mount is brilliant.
caster_201281521724_Rubber_Caster_Wheel.jpg


The flat plate that's anchored to the V-brake bosses is a great idea (mine was a disc-brake frame, no V-brake bosses). Such a plate would allow for several mounting-hole sets, so the shock could be moved forward or back (depending on the length of the shocks you experiment with). If the cheap-o WalJunk shocks were too craptastic, a more-expensive air-shock could dramatically improve the shock performance, with your budget being the only restriction.

I planned on a 24-inch (or 20-inch wheel with fattie moped tire= 22-inches, very flat-resistant) on the rear wheel for a future build to make the bike a little shorter overall. I wanted to show that it was possible to do with just a hacksaw and a drill. I put it together while I was renting a bedroom in a 2-bedroom apartment. The bottom pic is the money-shot of Dogmans frame-set. By leaving the top-tube on the rear frame section still attached, it provided a perfect place to hang cargo boxes.

Between your method and Dogmans, making a FS longtail is very easy and cheap, I highly recommend having a second E-bike like this as a back-up. Sooooo cheap to put one together.

"Full-Suspension Longtail 2.0"
http://endless-sphere.com/forums/viewtopic.php?f=28&t=19131&p=278822#p278822
file.php


file.php


file.php
 
Mine works well, has a decent air shock. I just don't like the sluggish handling, and weight. I was thinking of converting it to semi-rigid so I can load cargo on the rear triangle.
 
BarkMau said:
One of the goals of the project is to make a bolt-on solution; which means, no cutting and no welding at least on the main frame. I am confident on the way I linked the shock to the frame (custom plate which bolts on the brake bosses).
Click to expand...
Its good that you're aware of the need to have confidence in the shock absorber/spring mounting. That short shock is pressing into the center of the long tubes that are your stays, however. The stays will be subject to a repetitive flexing for which they aren't designed.

A much better point of attachment would be in a way that transfers the force to the junction of the top tube/seat tube/rear stays. A longer motorcycle or moped shock would span that distance, have better damping, and most have a five position spring preload adjustment. They also come in about any length you'd need.

Longtails FTW!
 
dogman said:
Love to see more FS Frankebikes.

FS Frankenbike it is!

Though the shocks on mine are a joke, it's worked amazingly well for me.

Glad to hear!

Interesting shock mount bracket. Is that a repurposed caster?

Correct.

If you have not tuned it yet, this is how I did mine. I took the original frame and fork, and put wheels on it. Then I measured the height of the pedal crank from the ground. Then when I put on the rear assembly, I made sure the crank height was identical. This makes sure that you haven't ended up with a funny fork angle. Mine ended up riding perfect, with no funny handling issues.

Pretty straight forward, fool-proof procedure. I'll be doing that to be sure I end up with the right geometry.

But I do think you must center that swingarm in the frame.

Totally agree.

Id take a hacksaw to the long part of the BB, or find a cheap bb that is equal in length to install on the swingarm.

Are there any BBs that have the same length on both sides? Or, once you take it apart both sides separate?

But if you bolt it, which should work fine really, I'd think that some kind of torque arm like device might be good.

Great idea. I think some sort of reinforcing arm is mandatory.
Thanks Dman, any pix of your bike?
Click to expand...
 
spinningmagnets said:
...mine has been dis-assembled since I moved to another state (only have a one-car garage right now).

Sorry to hear that man.

While mine was running, I loved it. I had it adjusted so that my feet were flat on the ground when I was at a stop. With fat tires it ran like a dream floating on a cloud.

Hopefully, I'll be able to reach the ground comfortably when sitting on the back rack.

I planned on a 24-inch (or 20-inch wheel with fattie moped tire= 22-inches, very flat-resistant) on the rear wheel for a future build to make the bike a little shorter overall.

Would that be a regular bmx type rim?
Click to expand...
 
veloman said:
Mine works well, has a decent air shock. I just don't like the sluggish handling, and weight. I was thinking of converting it to semi-rigid so I can load cargo on the rear triangle.
Click to expand...

Semi-rigid. Do you mean something like replacing the shock for a rigid piece? If you want to load it up and are equipped with an air shock, wouldn't it be enough to just increase pressure?
 
gogo said:
BarkMau said:
One of the goals of the project is to make a bolt-on solution; which means, no cutting and no welding at least on the main frame. I am confident on the way I linked the shock to the frame (custom plate which bolts on the brake bosses).
Click to expand...
Its good that you're aware of the need to have confidence in the shock absorber/spring mounting. That short shock is pressing into the center of the long tubes that are your stays, however. The stays will be subject to a repetitive flexing for which they aren't designed.

A much better point of attachment would be in a way that transfers the force to the junction of the top tube/seat tube/rear stays. A longer motorcycle or moped shock would span that distance, have better damping, and most have a five position spring preload adjustment. They also come in about any length you'd need.

Longtails FTW!
Click to expand...

No doubt the shock and attachment you suggest would provide superior suspension. I'm hell bent on a bolt-on solution though. I'll keep it in mind.
Appreciate your feedback
 
My longtail stopped being sluggish when I put a 5304 on it. :twisted: I run it at a mere 2000w of 48v, but I zoom away from cars at the stop lights.

But loaded up, it never handles like a light bike of course.

For those not wanting to hunt it down, my build thread here.
http://endless-sphere.com/forums/viewtopic.php?f=6&t=28389&hilit=bouncing+betty

I need to update it, I put my 56 tooth crank on it yesterday. I'm riding it fast more and more now that a new grocery opened only 5 miles away. I used to have to crawl to a store 9 miles away. 10 mile round trip I can go 30 mph.
 
For low power you can have FWD or 2WD, but for high power...FWD is just not safe.

edit: for those who are going to go FWD, regardless of warnings, use TWO torque-arms. One of the pics floating around the archives is a high-powered FWD that started acting funny, pulled over and both drop-outs had snapped. If he had not using two torque arms, it would have likely been a face-plant into traffic. And...one torque-arm for FWD? injuries to my body are not worth the risk...just to save the extra $20.
 
I seriously considered making my bike a fwd. I have liked front hub a lot on the street, but front motors on suspension forks never work that great in terms of suspension function, and I wanted good suspension on both ends.

As for dangerous, 3000w front motor got tricky for sure, but only if you grabbed full throttle while entering a corner. Leaving a corner it was fine.

4000w was dangerous. Tricky any time you grabbed a lot of throttle. To run that much power in a front fork, I had to weld a special fork to hold the torque arms better. Hose clamps couldn't hold it.
 
I have yet to finish mine to test it's usefulness, but there's plenty of ideas in it to ponder:
http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=31255
 
Since you're likely to load it down, make he rear a 20" and put the hubmotor in it. That will give you lower gearing and better all around performance. I hope that caster is rated for 400lbs or more, because it looks kinda thin to me.
 
John in CR said:
Since you're likely to load it down, make he rear a 20" and put the hubmotor in it. That will give you lower gearing and better all around performance. I hope that caster is rated for 400lbs or more, because it looks kinda thin to me.
Click to expand...

I'd like to use a 20" in the back, however 24" is what I have. Maybe in the future. If the linkage works, switching to 20" should be pretty straight forward. I thought the same thing about the caster but the wheel was all metal. I'll be keeping an eye on it.
 
AW had spoke problems with 20" wheel. Radial laced But that was a stock 9c rim and stator I sent him. Surely it can be done stronger.

I have wondered how nice a FS longtail you could make with a nice strong scooter wheel with a cast rim and fat tire. Get that load as low as possible. Mine carries too high, and you do feel it. I try to put all the heavy shit in the lower panniers, water, batteries, canned foods, milk, beer. The big upper boxes high on the deck carry the lighter stuff in the grocery bags.

Loaded for touring, all the extra camping gear ends up loaded very high and makes it harder to ride. But touring I need to ride slow to extend range, so it's still tolerable enough.

In the end, I just put the longtail on a trailer, and camped in my car when I did what little touring I did this summer. The place I wanted to ride was 150 miles away. That made the riding I did much nicer, loaded only with battery. It was nice to carry a generator in the car to charge.
 
fat 20" on cast rim seems bullet proof. Right now I'm looking at Michelin gazelles 17x3.0 on moto wheels which should come a bit under a 24" bicycle wheel size. we'll see how that turns out.
 
dogman said:
AW had spoke problems with 20" wheel. Radial laced But that was a stock 9c rim and stator I sent him. Surely it can be done stronger.
Click to expand...
Yes, it can--just using "real" spokes instead of the crappy ones that come on those wheels helps a lot. ;)

If you look in the CrazyBike2 thread starting in maybe July-ish, maybe August, it should show the new Sapim spokes used on a similar Crystalyte wheel (to replace the crappy ones it came with that just kept snapping fast until I had at least 10 broken ones) in an odd lacing suggested by JustinLE. It's radial on the left side, and 1x on the "drive" (right) side--but to help the spokes go into the rim straighter to put less strain on teh threads, they are bent a couple cm in from the end of the spoke, for those 1x spokes.

So far it survived WAY better than the other--but I *have* lost two spokes--both from severe potholes (one of which I couldn't see under the puddles in the rain, and was new because of the rain and cars going thru it, I guess, cuz I know where all of the dangerously large holes and bumps are, so I can avoid them even if I can't see them). That first big pothole is at least a couple inches deep, and I was probably going 18-20MPH when I hit it--hard enough to flatten the rim itself, too. (cheap one that came on the Crystalyte wheel, but still a doublewall). I don't remember what broke the other one.

But so far no other spokes have gone, evne with some of the other stuff I've hit that I had no way around it at that instant.


All that said--if I had *any* kind of suspension back there other than the flex of the long long frame itself, I doubt I would be having such problems with the spokes in teh first place (some, yes, but not like this).
 
BarkMau said:
fat 20" on cast rim seems bullet proof. Right now I'm looking at Michelin gazelles 17x3.0 on moto wheels which should come a bit under a 24" bicycle wheel size. we'll see how that turns out.
Click to expand...

Pedal strike will be an issue - if you pedal in turns - which seems silly @ 30+ MPH.

Looking forward to seeing how well this machine performs 8)
 
Assuming we are still talking about a frankenbike longtail, you'd tune the pedal height to the exact same as before, including any lengthening of the the front forks.

And then there's the "who's pedaling" method. Long as you don't hit pedals unless turning it can still be tolerable to pedal with a pretty low bb.
 
With the frankenbike longtail, it would seem to me that's it's easy to rotate the swing-arm rear downwards (via the shock mount location, or adding spacers) to dial-in the pedal-height?
 
spinningmagnets said:
With the frankenbike longtail, it would seem to me that's it's easy to rotate the swing-arm rear downwards (via the shock mount location, or adding spacers) to dial-in the pedal-height?
Click to expand...
Exactly!
 
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