Full suspension longtail bicycle (Folding)

[spinningmagnets]

2ndShockMount.JPG (133.46 KiB) Viewed 684 times

ShockMountUpsideDown.JPG (108.71 KiB) Viewed 684 times

Since the tubes on this frame are aluminum, The 4 U-bolts that are now holding the shock-mount plate are placed over two saddles made from a short length of steel pipe sliced along its length, to spread out the force so they wouldn’t crimp the tubes.

If I couldn’t find steel pipe that was the best ID to snugly fit over the frame tubing, I would have gotten slightly larger diameter pipe and filled the void with JB-Weld (metal epoxy). I would’ve rough-sanded the inside of the pipe to help adhesion, and rubbed Chapstick (or any other convenient waxy substance) on the frame to prevent it from sticking to the frame.

The all-thread rod is now passing through a Brass Pipe T with three ½â€ threaded holes. I installed a brass bushing into the center ½â€ hole (actually about ¾â€ ID, as ½â€ refers to the ID of the intended plumbing pipe diameter), and this bushing is a ½â€ OD to 3/8” ID. I bought a ½â€-13 tap, and re-threaded the bushing ID so that the all-thread rod fits snugly. The bottom of the T simply has a snug hole drilled through it.

The two smaller central U-bolts are placed around two 1/2” pipe plugs that are threaded into the brass T. The common cast roundish brass T's would've worked fine, but when I saw the squarish billet brass T's, I felt they were a little stronger

If this brass T seems to work well enough, I may fill it with JB-Weld. In my opinion, the aluminum plate and brass T only hold the rod in proper alignment, and probably will not see much in the way of side loads. The neck of the shackle has been reinforced with an all-thread-coupler which looks like a long nut.

At the bottom of the threaded rod is another 1/2" to 3/8" bushing (re-tapped to 1/2"-13 threads) and a common cast brass T with all three ports having 1/2" pipe thread. Brass can be drilled, tapped, and cut with a hacksaw fairly easy, while still being stronger than aluminum,...plus I like how brass looks (Ex-Navy bubble-head). The brass T was hacksaw-cut and file-shaped to fit in the crotch of the chainstays.

Acquired a 4" plastic clothesline pulley from Home Depot ($5) that is a perfect fit over a bike chain, and a $5 used thrift store inline skate set with 10 wheels/bearings total...Thanks AW and torker!

If this shock mount works well, I’ll make up something that looks better after I resolve the rest the issues and the bike is functioning. “When you’re trained to use a hammer, everything looks like a nail”

[def215]

“When you’re trained to use a hammer, everything looks like a nail”

haha. i guess youre hitting that nail on its head then...lol.

looks good so far. looks like it can be emulated also for future users . are you going to run one long chain from the front pedals or you gonna put an intermediate shaft in some place along in the frame?

[John in CR]

I had to do a double take. I thought that was an S&M saddle on the first pass.

[spinningmagnets]

def215, right now it will be a single long chain, the plastic pulley and skate bearing is for an idler wheel at near the halfway point. However, for anyone else who's interested, it would be very easy to add a simple jackshaft. Also a 3-to-8 speed hub could be used as the jackshaft (which would also allow a small single chainring on the BB).

If I kept the same 26" rear suspension arm and then swapped in a 20" wheel (adds 3" plus the existing space), there would be plenty of room just in front of the rear tire for an RC-drive, roughly 6"...the length of a dollar bill.

If I used a 3-speed hub as a jack-shaft and then a Sram Dual-drive on the rear wheel (with two splined ENOs), an RC motor would then have 3 gears, and I would have 9 pedal-gears (without the need for a giant front chainring, such as the popular 47T-52T).

John, Soooo...S&M is the first place your mind goes when seeing that?...I want to party with you, my friend! (I guess then "hardtail" might describe the rider more than the bike!)...of course I will cut the extra length off the U-bolts and probably use acorn nuts to cover the stubs. The shock mount may yet evolve depending on driveline and seat solutions, but I believe this style of shock mount is fairly easy, affordable, and adjustable to fit the majority of frames that are likely to be used.

Full-suspension is supposed to make the ride more comfortable, not more painful!...

[John in CR]

SpinningMags,

You're going to have put your latex suit on for riding instead of lycra.

[amberwolf]

Seeing it in this form reminded me that CrazyBike1 would have been a little like yours is turning out:
http://electricle.blogspot.com/2009/01/ ... ea-or.html
But at the time I had no real shocks available; I was trying to see if I could do it with a shockmount seatpost but there was not enough spring. I thought seriously about using a front fork, but IIRC the only useful one I had was the one I needed to use as the front fork itself.

Then I decided to go simple and make it a hardtail, and CrazyBike2 that you all know and love came about.

[dequinox]

Wow nice use of the air and pipe fittings! I don't think I would have thought to use off the shelf stuff like that for this application. Looking good so far spinning, are you planning to add cargo capacity to the longtail design similar to an xtracycle?

[spinningmagnets]

Based on a thread last year, one cargo rack idea that was tossed around was a 3-pivot mount. The lower red dot is the location of the rear supension pivot to help you visualize the rear suspension moving up and down. If the bottom pivot of the rack support-rod is moved to the rear, the rack would move up when the bike hit a bump.

If the support-rod bottom pivot is moved forward, the rack would actually be pulled DOWN when the bike hits a bump. When the upper and lower support-rod pivots are aligned with the frame-suspension pivot, there will still be a small amount of rack movement, but very little. Plus the resulting rack could hold very heavy cargo. I've seen several commercial racks like this, but they are not common.

rearSuspensionRack.jpg (47.2 KiB) Viewed 650 times

[John in CR]

I missed that discussion last year. That seems like a perfect rack, and it avoids all the weight hanging off of the seat post which puts a lot of pressure on the rear suspension components as well as the seat post.

[docnjoj]

That is seriously fine engineering, SpinningMags. I just noticed your initials would be SM. Hmmmmm............!
otherDoc

[spinningmagnets]

This pic is from Dogmans suggestion that its useful for a bike to be able to fit on a bus rack (also helps for apartment or garage storage). Once folded with 26” wheels, its 35” from axle to axle (89cm), and 5-foot / 60” (152cm) overall from tire edge to tire edge.

FSLB_Folded.JPG (90.68 KiB) Viewed 415 times

This pic is inspired by Ypedal who is an advocate for a 20” wheel on the rear. Using the stock 26” suspension arm, there is room for a 4” / 100mm diameter motor. The large RC motor AussieJester uses is only 80mm in diameter, and it’s quite a powerful beast.

The derailleur hangs quite low, so if I end up going this route, I may use an internally-geared Nexus or a SRAM Dual-Drive with two broached ENO’s

FSLB_20_RC.JPG (94.88 KiB) Viewed 415 times

[John in CR]

...SpinningMags. I just noticed your initials would be SM. Hmmmmm............!
otherDoc

Doc,
If his username was Spinning&Magnets, then you'd be onto something.

[spinningmagnets]

Used the in-line skate wheel (smaller diameter) as an idler. The clothesline wheel already had a perfect groove in it, but the larger 4" diameter would have been more difficult to mount on this particular project. Wheel material (urethane, hard-rubber?) got soft when warm, had to let it cool on occasion to cut better.

I already had a coarse round-file and a sawzall blade handy, and they worked well. Wear a leather glove when holding the cutting tool, and have the spinning wheel pull the tool away from your crotch. Also point yourself and the job so that if the spinning wheel pulls the tool out of your hand, that it doesn't launch it across the room and stick into someone. Spread out an old sheet to collect all the little shavings and wear some type of glasses, even if they are sunglasses. Thanks for the suggestion Torker and Amberwolf.

White sleeve is the barrel I cut from a fat ink-pen, I used it as a bushing-rest when the all-thread was spinning. the idler-wheel shaft on the bike has jam-nuts spaced to allow the wheel to slide back and forth about 1-1/2 inches while shifting the chain across the rear gear-cluster.

FSLB_idler1.JPG (66.12 KiB) Viewed 375 times

FSLB_idler2.JPG (116.53 KiB) Viewed 375 times

FSLB_idler3.JPG (99.02 KiB) Viewed 375 times

[zap]

Nice build spin.

That's exactly how I carved a roller blade wheel for an idler on my bent and also for a small pulley on my first pedgen.
I turned it with a drill also and was trying all kinds of stuff to lathe it. I finally ended up using a circular saw to quickly and cleanly remove the soft urethane to get a rough shape then clean it up with a rough file... it seemed to work the best.

[spinningmagnets]

I have an idea I could use some input on, to see if I'm missing something. I like how the bike folds up when I pull a pin from the rear shock. I'm likely to use a locking ball-pin on the rear-most shock joint.



Now that this beast has a chain I can start working out other issues.

When the bike folds, the bottom half of the chain droops a lot. Several ways to deal with this, but...I'm thinking I'd mount an ENO "Dos" to the suspension pivot. Run one chain (a half-link style) from a big single front chainring to the ENO joint, and then a second conventional chain runs to the rear gear-cluster and derailleur.

I "think" the trials crank from the resources sticky has freewheel threads on the right crank, in order to allow the front chainring to freewheel. I could just cut off the threaded section that has a square-tapered shank hole. Are trials cranks right-handed threads, or LH? Will the ENO Dos work like this (I may remove the pawls so it rotates in both directions...)...thoughts?

http://sickbikeparts.com/catalog/product_info.php?cPath=21&products_id=35



Edit: found a great post about ENO's on trials cranks with lots of pics concerning a tear-down:

http://observedtrials.net/vb/showpost.php?s=691c0e51b5e4944e3d543653e4899ec4&p=285967&postcount=7

ENOtrialsCrank.jpg (29.72 KiB) Viewed 364 times

[amberwolf]

So you mean, run the bottom chain *over* the joint instead of under it, riding on the ENO as an idler?

Assuming the ENO spins the right way or you take out the pawls, it should work, but:
--It won't allow the sideways movement across the cassette that the other idler does.
--I think it'll change the derailer tension differently (less?) than if it were spanning the bottom naturally, as the shock pivots.
--Won't you need another idler roller under the chainstay forward of it, to keep it off the frame as it goes down to the front chainrings, especially the smaller ones?

[grindz145]

I just got a Monty trials bike. If you REALLY need to know I can take it apart and figure it out

[spinningmagnets]

The idea is to tave two separate chains instead of one long chain. When the bike is rolling the chains will be near in-line, and when folded, they will be shaped like an upside down V, with the two-cog Dos as the joint. The derailleur on the rear provides some slack, so the rear chain could be a normal one.

The front chain would not neccessarily need a sprung idler wheel, so if using a half-link style chain, a chain could be made in the proper length to run from a large single chainring onto the Dos while being just the right length to fit the ENO joint into the drop-outs. Just a thought...

The trials crank is about $25 and the ENO Dos is $110 so I'm not going to rush into it. Certainly a small idler wheel on the bottom of my chain will work for now.

FSLBfoldedChain.JPG (87.59 KiB) Viewed 355 times

[amberwolf]

OH! I totally did not grasp that possibility when looking at it before.

[gogo]

I have an idea I could use some input on, to see if I'm missing something. I like how the bike folds up when I pull a pin from the rear shock. I'm likely to use a locking ball-pin on the rear-most shock joint.

When the bike folds, the bottom half of the chain droops a lot. Several ways to deal with this, but...I'm thinking I'd mount an ENO "Dos" to the suspension pivot. Run one chain (a half-link style) from a big single front chainring to the ENO joint, and then a second conventional chain runs to the rear gear-cluster and derailleur.


http://sickbikeparts.com/catalog/product_info.php?cPath=21&products_id=35

I don't think the dos allows two chains at the same time. Also, the lever action on the shock absorber link seems a potential problem. Can it compress far enough to "pop" into a reverse position? It looks like you really need a shock that will go all the way to your plate.

I've followed this thread since you started it and only this time caught doc's SM reference.

[docnjoj]

Not my fault, Gogo! John started it!
otherDoc

[docnjoj]

There are true dual frewheels that allow 2 chains at a time but the Eno is not one. I think Cyclone uses something like you (SM) want. As you said there are BMX types with different gears and reverse freewheels on opposite sides of the wheel. The folder is really brilliant!
otherDoc

[docnjoj]

Oh yeah! the Mongoose CX240 uses a 2 sided reverse freewheel so they may sell the part (hub) or wheel at reasonable cost. I made a double sided one from an old SA 3 speed hub for my grandkids CX240 and it worked fine. Close machine fit and JB weld held the freewheel on the left side. I may be able to find the prototype if any interest.
otherDoc

[vanilla ice]

I want a FS stokemonkey..

[John in CR]

SpinningMags,

Thanks for throwing that picture up of how it will fold. I hadn't thought about making sure I have clearance to make sure the rear will pivot all the way under and to the front, and I definitely want to copy that folding. With the front wheel off and that folding, my 2 wheel land rocket will be quite compact (for a big bike) for tossing in the car.