Catrike Speed chain falling off
 

I have a Catrike Speed with a two-speed kickshift coaster-brake hub and the chain keeps falling off. How do I prevent this from happening?

Chain to loose? Chainline ok? Chain sticky and/or worn?

Chains fall off when there is too much slack. On a coaster brake bike slack is removed by loosening the wheel axle nuts and moving wheel backwards. Not familiar with Catrike Drive chain. Post some pictures and you will get better feedback.

A recumbent trike with a coaster brake? I have been the recumbent guy at the shops I've worked ever since I had my Avatar 2000 and I've never seen this spec as stock. The chain path and the tubes and pulleys certainly would make a non der tensioned chain run interesting.


We need more info to be better able to help. Photos are a real aid to our understanding what hasn't been yet mentioned. Where does the chain derail? Front, rear of in between? Andy.

@Andrew R Stewart ;, good point about chainline. Is there one idler pulley on the bike? Two idlers?

It is possible the idler pulleys also need to be designed to be more rigid than stock to take up the tension plus pedaling and braking forces. I know some vintage tandems use steel pulleys.

I've never known this hub to be an option with a Catrike. Possibly a poorly executed retrofit in a questionable application.

Can you describe how long it should be? How is yours configured?

I'm not getting the point of your question. I do have a 2 speed kickback coaster brake hub, but it's in an upright bike with horizontal dropouts and therefore bears virtually no resemblance to your application. A Catrike uses a circuitous chain routing and any I've seen up close had vertical dropouts necessitating a tensioner or derailleur at the rear wheel. This precludes use of a coaster brake for this application.
You need to give us more detail before anyone can address your question. Some photos of the drive train would help.Did the bike come from the factory with the coaster brake hub?

I have a physical condition that inhibits my muscles in my hands. Therefore, I can't use handbrakes.
so, I just modified the bike. Instead, I have a coaster-brake hub. I have attached a picture of me riding. If you can blow it up, you'll see the chain and the coaster-brake hub in the back. The hub is a two-speed Sturmy-archer kickshift coaster-brake. the problem is I don't seem to be getting the right tension on the chain.
Thank you for any suggestions .

OK, so it is a retrofit. Are the rear wheel dropouts vertical or horizontal? Also, are any of the guide pulleys that the chain is routed around adjustable? If so, you should be able to tension the chain that way even with vertical dropouts.
However, even with sufficient tension on the chain, any twisting of the frame while riding could still derail it because the frame and chain are very long.
Using a rear cog with a built in chain keeper would at least keep the chain from derailing off the outside. Shimano makes such cogs for the Alfine hub. They are the standard 3 lobe type that would fit your two speed.
http://i68.tinypic.com/2qtcwly.jpg

As Dan says, the Catrike isn't designed for a kick-back hub. You need something that keeps both the top and bottom runs of the chain under tension to keep the reverse tension from derailing the chain. Your picture shows that the return run of the chain is very loose- it really needs to be improved.

Does the return run of the chain run over a pulley or through a chain tube? If it's the stock setup, then it runs through a chain tube. In that case, there's no good way to tension the return run of the chain. The chain tube will create a bunch of friction if you put tension on it.

I would replace the bottom pulley with a pair of pulleys, one for each run of the chain. I would also install chain keepers on both pulleys to keep the chain from ever coming off either pulley. Since you're relying on coaster brakes a derailed chain means no brakes- not a good thing. Terracycle makes chain pulleys and keepers of all sorts and they're used to coming up with custom solutions: Idlers : TerraCycle, Exquisite Recumbent Parts & Accessories

After installing the two-pulley system, I'm going to suggest you extend the boom enough to keep the chain under tension on both the drive and return runs. This will compromise your leg-length adjustment, though. Your frame wasn't built to adjust the rear wheel position (like Dan's upright bike) so you have to accept some compromises.

The alternative solution is to abandon the kick-back shifting. Do you have enough mobility/dexterity in your hands to shift gears? There are setups using a one-way clutch on the cranks that pull a cable to operate brakes. They are used on handcycles to allow paraplegics operate their bikes/trikes. Here's a video of one in operation:
A friend has a similar setup on his hand-and-foot powered recumbent bike. It allows the bike to have backpedal brakes and a Rohloff internal gear hub (although it would work with derailleurs also).

Good luck on your endeavors.

https://www.bloomfieldbike.com/merch...nRightSide.jpg