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Sunday, May 18, 2008

HOW TO BUILD AN INEXPENSIVE SUSPENSION RECUMBENT BICYCLE AT HOME PART 4


Now that the seat is installed, it's time for the job that will rack your brain big time: chain management. On regular bikes this is pretty obvious, the chain goes straight from the chainring sitting in front of the rear wheel not too far ahead.

In our case, the chain has to make a few detours to get from the chainring to the rear wheel and must avoid a whole bunch of things on it's way there and back. Before you start making your chain management set up, make sure you install everything on the bike, brakes, cables and every little doodad that goes on there. You must know what will be in the way of the chain before you install it. Remember, we're not working with plans here! One of the easiest ways to bring the chain from the rear to the front is with black PVC type tubing. I use the kind that is put in the ground for lawn sprinkler systems. 100 feet for $12, it should last you a lifetime. Those types of tubes usually last one season, so all the extra is not for nothing. It is surprisingly quite, you just have to make sure you secure the tubing with a good amount of duct tape strategically placed so the tube doesn't move with time. Leave the very front and back of the tube loose so that the chain can move when shifting from one gear to another.



That takes care of the top part of the chain, now for the lower part or the return section of the chain. When the chain is moving in the lower section, it isn't under tension and we can get away with less strength in our deviation set up. I use a grinded rollerblade wheel secured at the old bottom bracket by using a front wheel axle jerry rigged on the left bearing cup. It holds pretty nice and is very quite. I allow the wheel some movement on the axle so the chain can remain more straight in its path back to the rear wheel. I also added another wheel which I made from an old printer bracket wheel that I attached to the clip that holds the front boom. I sandwiched an old derailleur wheel on it. I used that one to clear the top of the fork while the chain is on its way back to th rear of the bike. I could have used another rollerblade wheel type of arrangement there as well, but I already had that set up lying around.



Now at this point the bike can be powered. Before you start installing all the accessories and other little knick knacks, install a working rear brake and take it out for a ride to see if your prototype is actually functional. I did with mine and that's when I found out that...

IT'S A TOTAL FLOP!

Yes, sadly this is a possibility when you hodge podge a homebuilt bike together. Before I started this build, I figured there was going to be some flex when pedaling the bike caused by the rear suspension, but I wasn't expecting that much. The thing bounces around like a clown bike when under full pedal power from a dead stop. Climbing hills is just very hard labor and extremely slow. I had tightened up the spring on the cheapo shock absorber, but it wasn't enough.

Mind you, the suspension does its job while going downhill or when you're up to speed on the flats. But unless you want to train to get legs like Lance Armstrong, going on even the slightest incline is murder for your leg muscles. There might be a way to lock the shock when you need it or a better quality shock might work better, but I don't have the time or money right now. I need a working recumbent for a big critical mass event in 2 weeks. Not only does it need to work, it also has to be broken in, no time to do repairs on a big ride like that. So on with:

PLAN "B"



Plan "B" is my previous short wheel base recumbent that my son affectionately called the "Pocket Rocket". It is made from and old CCM mixte frame. It runs on a 20 inch rear wheel and a 16 inch front wheel. I had some elements like the front boom and brake bosses welded on by a welder for hire. Cost of the welds back then came to about $20. Next post will be about slapping the Rocket back together. Sorry about this let down, but things like these happen when you make stuff yourself from junk. Remember that practice makes perfect.

Til next time, ride safe and Godspeed.

Gerry :)

Homebuilt recumbent part 1
Homebuilt recumbent part 2
Homebuilt recumbent part 3

15 comments:

Glider said...

I am not sure how much curvature you can get away with in your black PVC, but if you could run the top of your chain close to the original bottom bracket, I bet you could eliminate a lot of the bouncing.

Gerry Lauzon said...

Thanks Glider, but it's too late for me. Maybe someone out there can give it a try and let us know.

Gerry :)

Tsuru said...

haha! that's an awesome go of a bike! just picked up an old Schwinn World Tourist to rebuild and tinker with, you site is become a bible for everything I'm trying to do!

thanks so much... you can see my two babies on my site just scroll down a smidget to here -> http://blog.tsururadio.com/2008/05/like-spoke-on-wheel-i-turn-i-turn.html


;)

Peace, love, & LPs,
Tsuru
http://www.tsururadio.com

Gerry Lauzon said...

Thanks Tsuru, you got some sweet rides there and your photography is top notch.

Gerry :)

Tsuru said...

thanks! I keep going back and forth on what to do with the Schwinn World Tourist. 5 speed, single speed, new fancy wheels, old school steel wheels... all over the place in my head.

First up, my front forks are a little bent, need to figure out how to bend them back.

There's a neighborhood yard sale this weekend, I hope to pick up some good spare parts 10 speeds!

=)

So, I know I'll be all over your site this weekend!

plutonium said...

couldnt u buy a replacement bicycle suspension spring part they sell them on theinternet and there weight load is 300 pounds so its probably stiffer?

Gerry Lauzon said...

The force applied by your back on the seat when pushing the pedals at full power is around 400 pounds. So I don't think that it would work. The problem with this design is that the geometry is all wrong. Thanks for trying to help anyways, always appreciated.

Gerry :)

Anonymous said...

hey, i just wanna say ur doing a great job helping out many people with your great advice. Iv shown this site to all my friends, it has helped us alot with repairing our bikes at a low cost and for free! i thank you greatly for that, however, i have a problem. I mainly ride suspension bikes and a problem i have is this;

since i cant paste a picture, this is hard for me to describe but ill give my best shot. Just infront of the pedal on the opposite side of the cog, is a bolt, underneath the suspension. This bolt is always getting loose after i have tightened it with an allan key but it still becomes loose when i ride my bike. Also tightening becomes hard because the bolt has two sides, one i tighten easily but the other is behind the cog which turns aswell when i try tightening the bolt. However i cant get my allan key inside to tighten it as the cog comes in the way.

As confusing i have made this sound, is there anyway you can help me? thanks in advance :)

Gerry Lauzon said...

Thanks for the great words. I know exactly what you're talking about. You need to tighten that allen bolt on the side of the chain rings(cog). You'll need to get a crank puller to remove it so you can get to it. Look up the article on the left sidebar about how to repair a 3 piece bottom bracket to see what I mean. Good luck and thanks for reading me guys.

Gerry :)

plutonium said...

woops i meant it could hold 800 punds

Anonymous said...

Hey, you could salvage that recumbent from being a total flop by redesigning your chain management system. The bounce in the suspension when you are pulling hard comes because you are pulling on the year along an axis angle steeper than the shock. This pulls your wheel into the shock each time you force the pedal. If you routed your chain so it appoaches the gearset at a shallower angle than the the shock, that would remove the upward force that is compressing your shock.

Gerry Lauzon said...

Thanks for the tip, but the frame is now in storage and I'm working on something else. I might give it a go later and I will surely try out your idea and others provided here by my loyal readers.

Gerry :)

ZAPPDOG said...

@ Anonymous
I have had the same kind of problem on my full suspension mountain bike.
(Crank Monster shown in the pics section) I had to make a tool to do something similar from an allen wrench. the short arm cut down and the long arm bent. I bought it at Canadian Tire for a couple of bucks. Another thought is to drill a hole in the crank just big enough for the allen wrench.
To keep it from loosening again buy a small tube of "Locktite" Red. Apply a drop on the threads and tighten down. It actually glues it. To remove it later, just heat up a bit with a propane torch.
I hope that helps you out

georgiaboy said...

beautiful bike,sir. i have a mountain bike i plan on rebuilding into a SWB 'bent, and i plan on using your build as a guideline. The only real change to the build i want to make is to use a two-chain approach; instead of running the chain straight to the rear wheel, i will run it to the original crank on the smallest gear, and leave the original chain on the outer gear. other than changing gear ratios, i think the suspension and pedaling will work the same as in the unmodified bike.
happy riding,
georgiaboy

Gerald said...

Good Luck Bro. You might have found the solution there. I truly hope it works for you because it sure didn't work for me.

Gerry :)