The Rezistor: figuring out drivetrain
I've mostly been working on figuring out what parts to use in the drivetrain. I've settled on #35 chain, which I believe is commonly used in go-karts. The guys at McGuire Bearing said this chain would be appropriate for the RPMs and torque of my application.
Here's where it got tricky: the Vespa axle is 17 mm at the location where I want to attach the driven sprocket, and the axle gets wider at both ends of the shaft - this means I have to use some sort of split sprocket. Apparently 17mm is an odd size, so I would have to have something specially machined. The bearing shop estimated 90 minutes of shop time at $1 per minute to modify a standard sprocket, so I decided to look for another option.
I went to the McMaster Carr website (thanks for the link, Reikiman) and ordered a flat 30-tooth sprocket and a split collar with an 11/16" bore. The parts arrived the other day, and the collar fits nicely around the shaft and screws down tight. The hole in the sprocket will need to be increased to just over 1" to fit on the axle, then I plan to weld it to the collar. Fortunately, I have a very kind friend from my scooter club who has the requisite machining and welding equipment and skills and has offered to help me with the work.
We'll also be building a mount for the right axle bearing. Probably just 2 or 3 plates stacked up and bolted to the motor mount plate, with hole in the last plate machined out for the bearing to fit into.
I also got an 11-tooth sprocket from McMaster Carr. It comes right out of the box, slips onto the motor shaft, tightens with set screws and a 3/16" key, and Bob's your uncle. At least some parts of this project are simple.
I made a stack of the motor, the motor mounting plate, the swingarm (old engine case), and the sprockets to see how everything fits up. I discovered that the 30-tooth driven sprocket is too wide to fit in the engine case. Once I get the sprocket in the right place on the axle, I'll need to slice out a section of the case for the sprocket and chain to fit through. Hopefully this won't weaken the case too much, but I can probably get my friend to help me weld on some additional reinforcing around the slot.
Can anyone recommend how much lubrication my chain and sealed axle bearings will require?
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Re: The Rezistor: figuring out drivetrain
Hey Jsept.
I have enjoyed following your build up.
I have a couple of suggestions that your machine shop may have already figured out.
I did a similar thing on my conversion as far as adapting a sprocket to a shaft.
If you plan on welding the sprocket to the split hub, I suggest machining a "receiving" step in the hub that will help keep the sprocket flat and concentric with the shaft hole.
Just a simple step on the split hub will help this. The gear will also put back in any strength removed from machining. The center of the sprocket will need to be opened up to precisely fit onto the new stepped flange.
I took it one step further so I could change out sprocket and have a range of gear selection.
I hope this helps.
Mike K.
Racermike
5 years ago I met Jesus and he total ruined my life. I have never been happier.
Re: The Rezistor: figuring out drivetrain
Thanks, Mike. That looks nicely done with the keyway and everything. I had a friend do some machining for me over the weekend and we ended up planning to do something very similar to what you suggest. We bored a hole in the center of the driven sprocket large enough to fit over the end of the axle. He is in the process of making a split bushing with I.D. equal to the axle diameter and O.D. equal to the hole in the driven sprocket. This bushing will keep the sprocket centered on the axle. We'll snug this up to the split collar that I have and weld the sprocket to the collar. This will allow me to adjust where the sprocket sits on the axle, then just tighten the set screws on the collar to clamp it in place.
One more difficulty we ran into is that space in the swingarm is kinda tight. It looks like we will have to do the sprocket welding while the axle is mounted in the swingarm, otherwise we won't be able to get the axle in. If I want to switch out the sprocket I might be able to get the axle out by removing the bearing, but more than likely I'll have to either cut out the axle or burn off the sprocket and start over with a new axle.
Jake
2020 Hyundai Kona Electric
Apollo City