Shake down cruise - 29 mph



Throttle cable coiled up by rear wheel, yet to be connected.

It's been a little while since I've posted a blog entry but that doesn't mean that I haven't been working on this project. I was able to find a way to mount the engine closer to the seat.  The belt just barely clears the brake calipers but it handles much better.  Here's a pic of the set-up so far.  I'm using a 69 inch 4L v-belt.  I tried a number of different ways to put tension on the belt with a rollerblade wheel as an idler pulley, but without flanges the belt would wander off the idler pulley and start climbing the drive pulley.  I found a Snapper idler pulley that fit perfectly and have been delighted with the result.  With that, everything stayed in alignment regardless of the belt tension.  

Dishwasher door spring pulls idler pulley into belt.

I attached a dishwasher door spring to the tensioning mechanism and put some linkage on the other end so I could have tension controls up front.  In this close up, you can see the black idler pulley attached to a chrome piece of square tubing, nested inside a larger piece of square tubing.  I canibalized this tubing from a retail store clothing display stand I bought for pennies a few years ago, it came in handy.  Up front, the linkage is attached to a lever made of steel flat bar and affixed to the bike frame using a 1 5/8" muffler clamp from O'Reily (a.k.a. Checker) Auto Parts.  When released, the spring pulls the idler pulley into the belt and engages the drive pulley.  I used a hose clamp to attach an "L" shaped stop to the bike that the tension lever can rest against when the belt is disengaged.  I got it to this point at 10:30p Saturday evening.  It was far enough along that I felt it was ready for a little test drive.  I added oil and fuel to the engine (it was brand new and shipped with no oil) and started it up.  It's sure a nice running little engine.  I then peddeled out to my street at about 6-7 mph.  I released the tension lever and engaged the belt and the engine took over without a hitch.  I didn't have a way to measure speed but it felt like 12-15 mph with the engine at it's lowest throttle setting.  Since all was going well, I kept going, about two miles over all.  No problems.  I opened it up for small section just to get a sense for the top end.  It's not yet broken in so I didn't want to overdo it.



Tension lever attached to bike frame with muffler clamp.

It was also pretty late so I shut it down to keep the neigbors happy, although it isn't very loud.  Sure nice to have the option to pedal.  On Monday after work, I took it out again.  This time I had my GPS with me so I could measure speed.  I opened it up again for a short distance and got up to 29 mph.  Not too bad, and quite a bit faster than my calculations, which I had set for around 20 mph at 3600 engine rpm.  Either my math is off or the engine is turning faster than 3600. Probably a little of both.  I also found I was also able to start the engine by putting tension on the belt while peddling.  This engaged the drive pulley and turned the engine over, starting it up.  Nice.  I'd still like to attach the throttle cable (I was reaching behind me to control the throttle) and put the kill switch up by the handle bars.  I'll probably rework the tension linkage so I'm pulling to put tension on rather than pushing to take it off.  Should be easier on the linkage components.  There's a bit of engine vibration through the frame but managable.  I'll explore the idea of vibration dampening. And it would be nice to have some front suspension.  I have a slightly larger drive pulley if I wanted to increase top end, but that was back when all I thought I'd get was 20 mph.  I think 29 mph is just fine for now.  We'll keep working on the refinements!