Last modified: 2026-01-21 22:54:18
< 2026-01-19 2026-01-22 >I took some photos of the engine and reversing gearbox so that I can work out how to lay them out. Annoyingly it is going to be quite long and thin, which is the opposite of the space I have available at the back of the car.
Reversing gearbox reference pics for CAD:
Front sprocket on engine:
The chain has to sit within the lines of the housing, so can't exit at a particularly extreme angle.
Bolt holes in cylinder:
Do we need to bolt this steady or can it simply be ignored? (Update: I think it can simply be ignored, seems to be used to hold bash plate, not to support the engine).
Bolt holes on bottom of engine:
These are I think intended for mounting footrests, but can you use them as engine mounts?
If you sit the engine on the plane of those mounts, you need a gap for the starter motor to sit down into:
Engine and gearbox together:
Or slightly more compact:
But in this configuration the front shaft may not be lubricated, so potentially best to keep it level.
Does it actually make more sense to put the engine and gearbox at the front, and just have long chain(s) running to the back? If you leave the occupants in the same place, that would help with weight distribution, packaging, and engine cooling. Maybe that is the obvious thing to do? Why would you not do that? Because you're influence by cyclekart practice? But this isn't a cyclekart. Because you don't want a chain running through the cockpit? Because you don't want the extra weight of a chain running the length of the car?
Is it possible to have the upper run of the chain go above the plane of the chassis steel, and the lower run go underneath?
The rear sprocket will be larger diameter than the chassis rails, but the front sprocket may not - what then? Do you need it to go over chain rollers that route it around the rails? Potentially fine, just try to arrange the rollers to be on the slack run instead of the taut run, and put the gearbox at the back so the same run is taut regardless of forward/reverse.
I see now why historical cyclecars had the chain running on the outside of the car.
Having the engine at the front with a long chain run is too much trouble I think. Having the engine at the back is not too much of a problem as long as I can mount the gearbox on its side so that the output chain can come "forwards" to the rear axle.
https://www.geminikarts.co.uk/product/f-n-r-gearbox-engine-mount/
These guys are mounting it exactly the way I would want to - but doesn't that starve the input shaft of oil? And this bloke did the same thing: https://www.youtube.com/watch?v=nzS6ULBPoww
Update: I think I have a solution!
Who's to say I can't mount it like this?
Turn the gearbox around so the input shaft is at the back, then the output shaft is already in a good position to run a chain to the axle.
Plan for tomorrow:
And then things to order include:
And then design the front axle.
< 2026-01-19 2026-01-22 >