Can somebody check my “engineering”? (Pic heavy)

M

MauleSkinner

Touchdown! Greaser!
Joined
Oct 25, 2005
Messages
21,670
Location
Wichita, KS
Display Name
MauleSkinner
Background: I’m an old, fat guy with a beard who rides a recumbent bike, and due to work schedule (or lack thereof) I’ve done very little riding in the last 5 years, and that’s going to change. I bought an electric assist kit to help out until I get some conditioning back, and since recumbents are a little strange, I ran into a snag installing it.

The torque arm is supposed to look like this:
1742510047080.jpeg

But with the geometry of my bike, it would either interfere with the shift cable or end up with a very short arm: (note that in all of the following pics, the bike is upside-down on my work stand.)

1742510174698.jpeg

1742510338427.jpeg

My solution is to make a piece to fill in the axle support

1742510419814.jpeg

The support is 1/4” thick, the pieces I made are 3/16” thick, the same as the torque arm pieces provided.

Then comes a plate that goes over the axle and attaches to the plug piece with two 5mm screws:

1742510656685.jpeg

For scale, here’s part of the original torque arm:

1742510738248.jpeg

And finally, the washer and nut:

1742510783133.jpeg

I figure that the real weak point on the torque arm is where the two pieces are bolted together with a 6mm bolt, and between the two 5mm bolts, one of which is on a slightly longer arm, and the increased friction surface that I’ve got, it should be strong enough.

Any thoughts appreciated!

Thanks
 
I don't think it will ever get off the ground.
 
I know bikes and my wife’s got a Trek e-bike. Neither of us slept in a Holiday Inn last night, but we both think it should work. What’s the worst that can happen?
 
I don't think the part you made is any weaker than the part it shipped with and by the looks of the photo, you did a fine job of making it a snug fit around the flats.

I'd periodically check the 5mm bolts, but the failure mode of any of the parts looks relatively benign. It just won't be able to apply torque any longer and you'll have to pedal it back home by yourself.
 
Getting ready for a hill climb that has defeated many Kansas motocrossers…
1742942180235.jpeg
After the initial ride, I’m pretty satisfied…I set the assist at 2 [out of 5) and once I’m moving it doesn’t do a lot. Coming up to an incline, I switch it up to a 3 and I can keep my cadence and reasonable speed. Leaves me with enough energy to get onto the big chainring on descents later in the ride. 10 miles used maybe 10% of battery.

And yes, chicks dig the pasty-white legs and Tevas! :rofl:

Bottom line, I’ll be putting some miles on this year, getting into some kind of shape, and hopefully shedding a few pounds.
 
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