Full suspension longtail bicycle (Folding)

[spinningmagnets]

FSLB 001.JPG (199.52 KiB) Viewed 2414 times

A while back I bought a Mountain bike to get fat tires, full-suspension, and a front disc brake. I didn’t like the posture, so I modified it to be more of a semi-recumbent, similar to a beach cruiser posture. I was pleased except that when riding uphill, the rear weight bias made the bike somewhat wheelie-prone.

There is a longtail bike thread with many examples, and oldhaq’s bike inspired me to attempt adding a rear suspension arm to a hard-tail Downhill (DH) bike. Half of cheap MTBs have the bottom bracket (BB) as part of the frame, and the other half have the BB on the rear suspension arm (thats the kind I needed). I wanted to try attaching the BB square tapered spindle to the drop-outs on the rear of the hardtail bike.

http://endless-sphere.com/forums/viewtopic.php?f=1&t=9673&start=15#p151589

Most cheap bikes have integrated non-removable studs extending from the ends of the BB-spindle (the pedal axle). I found some mid-range Schwinns that had threaded holes on the spindle ends, which would allow me to use bolts (of my chosen length) to attach the BB-spindle to the drop-outs. I could then shim the odd bold length with washers (which I have).

My local bike shop (LBS, a big thanks to Big Poppi bicycles in Manhattan, Kansas) informed me that sealed spindle/bearing cartridge sets are available for $16 that also use end-bolts, and the spindles are available in several different lengths. The end-bolts for the spindle I acquired were M8-1.00 (metric diameter and thread-count) and the hardware store had high-strength "8.8" bolts of that type. Chose a length for maximum insertion, ended up shimming the excess bolt length between the drop-outs with two washers on each side. This bike had 8 gears and a rear disc, so the drop-outs were widely spaced, the spindle I used is 5" long.



Of course hub-motors can be fitted, and the extra frame space provided allows several types of non-hub systems to also be fitted. If someone desired to use a 24” or a 20” rear wheel, the shock mount could be extended to rotate the arm down so that the pedals wouldn’t strike the ground on turns.

If you have a rear suspension arm that uses the larger diameter bearings for the one-piece crank (found on many of the cheaper range of bikes) Sick Bikes makes a $20 adapter so that you can use the 3-piece crank-set with the square-tapered spindle.

http://sickbikeparts.com/catalog/product_info.php?cPath=23&products_id=56

second try 004.JPG

This pic is a close-up of the BB/drop-out joint

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[oldhaq]

Looks like you're gonna end up with a super comfy ride, wish I had had front susp on mine as well. I say had because it is no longer in action - a mate is now working on it's next incarnation which is something different again.
The bracket for shock to frame, I took some photos of mine which might give you some ideas for how you do yours. The extra rails on either side on the bottom of first pic were to mount the controller on one side and the BMS/wiring junction box on the other. I used hi ten b&n to mount it to the frame as there's a fair amount of force in there (thicker diameter bolts were intended but I never got around to it).
Getting chain clearance involved the most thought, adjusting the shock mount to get the main frame's rear dropout out height right, taking into account the movement when seated and over bumps. I had to use the chain guide cos there was a fair distance from chainwheel to rear sprocket, looking at yours though you might be ok.
Great to see, I look forward to see how it ends up.

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[Thud]

Good morning spin,
I am doing the Exact same thing to a Tidal force frame I bought from oatnet. I will add some pics to this post later tonight when I get home.
(I am debating taking it to the race in Ohio )

[BLUESTREAK]

How about that, a group of guys trying to make a longtail rear supension bike at the same time. I am making one as well I am using the front frame of a MERIDIAN TRICYCLE with the step through opening, the rear is from a steel frame that i bought from a member here,I haven't made much progress lately because I hurt my left shoulder last NOVEMBER and when you get a little age on you things don't heal very fast plus I have been working on my 2 meridian trikes and my VECTRIX scooter trying to make it into a trike as well. just too many projects. keep up the good work SPINNINGMAGNETS.

[spinningmagnets]

I am hoping to solve the major issues without welding (I do have access to welding, but I want to highlight possible methods for apartment dwellers without welders), though I may consider brazing a bolted joint I’ve made.

I also want to be able to return the hardtail frame to its original configuration if desired. I have high hopes for the results, but I also have 3 bikes and know that the hardtail (in original form) would be the easiest to sell, should I choose to not keep it.

For a shock shackle, I cut the end off of a turnbuckle with a billet center. Its from Ace hardware, and the hook-bolt threads are ½â€-13. I hope they are strong enough, and the threaded portion will allow easy length adjustment. By being threaded, it also allows easy swapping to a different shock, as I would only have to replace the shock connector, instead of the entire assembly.

AlBilletTurnbuckle.jpg (70.2 KiB) Viewed 2289 times

For the suspension arm, I chose one from the cheapest bike with the features I wanted. Ended up being steel.

26”wheel (could have easily been 24” or 20”)
BB is part of the suspension arm
3-piece crank with square-tapered spindle
Linear pull brakes (no side-pull calipers, also linears pop off easily with no tools to remove the wheel for storage or flat repair)

After a couple months of searching craigslist/thrift-stores for the right kind of used bike, I bought a new $100 “NEXT Power-X” from Wally-World immediately after finding a free bolted-end square-taper BB-spindle on a broken trash-day bike.

A crank-arm removal tool was only $12, and I wish I had bought it years ago. BB-spindle shown in pic is the one with studs (bad) instead of end-holes for bolts (good).

[SilverSurfer]

Yeah, full suspension! I was thinking of trying to mod out a rear suspension for my ride! Great idea! Good luck! SS

[vanilla ice]

Nice, now I know what to keep an eye out for. IIRC most of the BFnet/utility dudes use 20" rear wheels for cargo deck clearance and gear down.

[oatnet]

I want to see how this turns out, I love the idea!

-JD

[spinningmagnets]

Lifes been hectic these days, but every day I look forward to working on this, its fun.

Thud and Oatnet, I liked the Tidalforce frame as soon as I first saw it. Especially the low top tube, which allows the lower seating I prefer. That allows my feet to be flat on the ground when stopped, and I anticipate fewer accidents where I've bounced off the seat and cushion my fall with my testicles.

http://endless-sphere.com/forums/viewtopic.php?f=6&t=11765&start=0

Vanilla, I may yet go to a 20" rear tire to allow a low cargo deck and a single-stage gear-down on a non-hub motor. One experiment I may try is a geared hub (Bafang, Amped, Fusin) as a non-hub mount, somewhat "stoke-monkey-ish". I believe that configuration may have potential.

oldhaq, thanks for posting that pic. I believe an FS-longtail would be handy for quite a few people, and the more ideas posted then the more options are available. I dont know yet how I'll make the final frame/shock mount, but I'm slapping together a temporary one to get the beast rolling soon.

Thank you to everyone else for the encouraging words...if it wasn't for unimportant stuff interfering (like work and family), Id've been farther along! "I spent half my money on whiskey and women, the other half I just wasted" -WC Fields.

[spinningmagnets]

A big thanks to Blixt Landfill in Chapman Kansas for saving trash bikes for me, I've made several bikes from parts for friends and local kids, and the parts have also helped me at times. I rescued two road bikes from the crusher just today, they will likely go to local college students, via Big Poppi bikes.

First pic is the abrasive wheel I used in my cordless drill to remove a few cranks, a closeup of the carnage, and also the proper $12 crank removal jacking bolt I should've gotten a long time ago. Second pic is a temporary shock mount so I can roll the bike, and also help me visualize several options for various issues. It might even be strong enough to keep, but its placement interferes with the chainline. The plate crossbar is a rear wheel axle I had laying around, and this frame had some webbing (gussets) in a convenient location to thread it through.

I recommend stretching a string between the front chainrings and the rear gear-cassette to help see the exact chainline as soon as possible in the build. The chain will be long enough to need an idler wheel from a recumbent website, but the new seat-post and the permanent shock mount are the two big issues facing me.

I am positioning the shock front mount slightly above "inline" when unloaded so that under full compression loads, the shock will then be directly inline with the rod.

[John in CR]

I was wondering how you were going to anchor that shock. I see all that otherwise useful space for batteries or whatever, and just can't get myself off of an approach using 2 shocks. Sure they weigh more, but I figure most of the weight is gained back by avoiding the high strength required to support the end of a mono-shock due to the greater leverage. Also the seat and cargo loads will be supported near the end instead of hanging on the end of a lever, which also reduces the metal required in the frame.

Yours is coming along nicely. Any decision yet re electrification.

John

[amberwolf]

The chain will be long enough to need an idler wheel from a recumbent website

You may be able to use this instead:

clothesline pulley DSC02715.JPG (41.05 KiB) Viewed 2116 times

clothesline pulley DSC02714.JPG (57.05 KiB) Viewed 2116 times

I found it a while back at Home Depot when with a friend getitng parts to build up a floor for his storage shed. I think it was less than $4, and is 5" diameter "polymer" (feels/looks like nylon) pulley that actually has UV inhibitor in it! Groove in the pulley is about 1cm deep with steep but not totally vertical sides, and a round bottom. The hanger is stainless steel. Figured it'd be good for an idler/guide on CB2 once I got it back togther at the time, and have yet to actually try it.

I figured to bolt it on I'd drill all the way thru the horizontal crossbrace/capture bar in two places (one on each side of axle) with a small bit, then use the Unibit to make a large enough hole on the "outside" bar for a screw and driver to go thru it, to fasten to the frame of the bike or a mounting bracket.

Brand name is Penn Plastics, Inc, at http://www.pennplastics.com #40 pulley; made in USA, (bridgeport CT).

top one here
http://www.pennplastics.com/everlast-pulleys.html

middle one here:
http://store.pennplastics.com/everlast- ... ducts.aspx


Unfortunately online all homedepot has is these:
http://www.homedepot.com/h_d1/N-5yc1vZ1 ... ogId=10053
http://www.homedepot.com/h_d1/N-5yc1vZ1 ... ogId=10053
which don't look nearly as suitable.

[spinningmagnets]

Amberwolf, with the prices recumbent sites charge for parts + shipping, I might actually use that wheel! thanks.

John, certainly several ways to do this, two side shocks (like older motorcycles) would also make for a simple and sturdy cargo rack above it. The more I work with this rear-disc DH frame, the more I would recommend it to someone trying to make an FS-longtail. The rear disc and large 8-speed cluster means the chainstays are far apart (rear drop-outs had 5-1/2" in-between them), and also they were wide for the entire length of the chainstay because the frame was intended to use fat tires (has 2.50's). This means there is more room to allow more options, plus every part of this frame is very sturdy.

Since a downhill bike is pretty much only intended to pedal UP steep hills (and then roll down them very fast) they are sturdy and the front chainrings are small, to provide only low pedal ratio's and more ground clearance. The small chainrings mean that the rear gears have to also be small, so it came with a desirable 11T as the smallest cog. I intend to attach a single 48T-ish chainring to the front. Rear rim brakes can slip on acummulated mud, so rear discs are common on these.

For a motor? so much could happen in a month or two, but if buying today, I'd get the Ampedbikes rear geared hub. Good torque and 20-mph on 36V for $460 + battery/charger. I think I'd like to try de-lacing that hub and making it a non-hub drive. If I get it and then change my mind, I'd re-lace it and put that hub-motor on a second bike as a back-up. If RC component prices keep improving and RC issues continue to be resolved, I may go RC/LiPo. If so, I might change to a 20" rear wheel...

[torker]

Another cheap option for chain idlers is skate wheels. And bearings for them are cheap/free. I just took a longish 1/4 inch bolt and some washers and chucked the whole thing up in my cheapie drill press and used a 1/4 inch wood chisel and "lathed " a nice channel in the wheel for the chain to ride in. I wish I had some pics for you. I hope you get my idea.... I love yours.... I am ready to make my Rincon a full susp. longtail.

[amberwolf]

If you do use skate wheels, either use inline-skate wheels or use skateboard wheels. All of the regular skates I see at thrift stores have really crappy bearings in them that I could squish the outer races of with pliers...across the diameter! I used those first in CB2's steering tie rod, and when they started falling apart really fast, I switched to some out of a skateboard instead. Both came from a Deseret Industries thrift store, for like $3 for the skates I think (originally bought for rollers for DGA's friction drive) and IIRC actually was given the horribly crappy looking weatherbeaten skateboard--I guess they figured it wasn't worth the price marked on it.

Inline skates can be found on Freecycle and Craigslist as well as thrift stores; unlike skateboards they seem to be unwanted a lot. Most I've seen use narrow round-profile wheels but have at least decent-quality dual 602Z (I think) bearings in them, like the skateboards usually do.

I did try one of the skate wheels as a chain guide/idler once on CB2, but I think it had too much load on it because it chewed thru it very fast, in one of my early chainline experiments.

I've yet to get this clothesline pulley tested on there, but it will likely work ok as an idler with no load on it, and probably ok even with a load, despite having no actual bearing. We'll see, eventually.

[spinningmagnets]

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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 714 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