Aixam microcar - with a bike engine!
Discussion
So pretty much immediatley there are problems with the bike engine plan. The aixam engine bay is short and tall, whereas the bike engine is low and needs a lot of length for the chain to exit out the back of the gearbox (toward the rear wheel of the motorbike)
The chain can't come downward, as there is a lot of very important sump gearbox gear selector looking stuff in the way. Extending the sprocket outward from the engine (somehow) to clear the sump is an option - but after that the 2 driveshafts will need to be shortened to some comically short length in order to let the engine sit central in the bay. Im non-negotiably not having the engine off to one side.
A test fit with the crane confirmed this.
I mean it does 'fit' in the engine bay so thats a good start. But theres no way round the fact that an intermediate shaft is the best way to do things. Take the chain drive out the back of the engine to a sprocket on a driveshaft, across to another sprocket and down to between the 2 driveshafts of the car. See the finely cadded technical drawings...
By this point it was becoming abundantly clear that the exact placement of the engine was uncertain, until the lower driveshaft got sorted.
Reposting an earlier pic:
Without knowing where the sprocket was going to end up the engine's position would be uncertain. This car gets built from the bottom up.... So. Job 1 - make something that joins a sprocket to these 2 driveshafts. FIRE UP THE LATHE
Yamaha back sprocket (yes, its worn out. I am cheap) Mild steel metal disc for a sprocket carrier
Turned a step in the sprocket carrier
You ever buy something on ebay and not check the dimensions? I did that once and ended up with a comedy size universal tv remote for the elderly and blind. I also ended up with these puny bearings. Almost got laughed out the shop showing up with those...
Better. Driveshaft shortened to length, proper pillow block bearings, all fits. Back home for a test fit....
Something like that - right? Use your imagination - a bit of steel box section, squirts with the mig gun, tada we have our main centre driveshaft sorted.
I can hear the comments about 'welded front diff?!' already...
The chain can't come downward, as there is a lot of very important sump gearbox gear selector looking stuff in the way. Extending the sprocket outward from the engine (somehow) to clear the sump is an option - but after that the 2 driveshafts will need to be shortened to some comically short length in order to let the engine sit central in the bay. Im non-negotiably not having the engine off to one side.
A test fit with the crane confirmed this.
I mean it does 'fit' in the engine bay so thats a good start. But theres no way round the fact that an intermediate shaft is the best way to do things. Take the chain drive out the back of the engine to a sprocket on a driveshaft, across to another sprocket and down to between the 2 driveshafts of the car. See the finely cadded technical drawings...
By this point it was becoming abundantly clear that the exact placement of the engine was uncertain, until the lower driveshaft got sorted.
Reposting an earlier pic:
Without knowing where the sprocket was going to end up the engine's position would be uncertain. This car gets built from the bottom up.... So. Job 1 - make something that joins a sprocket to these 2 driveshafts. FIRE UP THE LATHE
Yamaha back sprocket (yes, its worn out. I am cheap) Mild steel metal disc for a sprocket carrier
Turned a step in the sprocket carrier
You ever buy something on ebay and not check the dimensions? I did that once and ended up with a comedy size universal tv remote for the elderly and blind. I also ended up with these puny bearings. Almost got laughed out the shop showing up with those...
Better. Driveshaft shortened to length, proper pillow block bearings, all fits. Back home for a test fit....
Something like that - right? Use your imagination - a bit of steel box section, squirts with the mig gun, tada we have our main centre driveshaft sorted.
I can hear the comments about 'welded front diff?!' already...
sparkybean said:
A diff?! How dare you! Didn't you know solid axle front wheel drive is the peak of handling dynamics?
I think you'll need a front diff. I've only got one point of reference for FWD fully locked diff (I broke it testing). It was okay on polished ice, and passable on snow once you got it to break traction, but on tarmac it was an absolute chore.
Tyre Smoke said:
Now if it was rear wheel drive, it would pull a useful wheelie.
This is mad. I can't see that sprocket set up lasting more than five minutes.
Its about to get much worse, dont worry. Though i do agree that if it was rwd being able to wheelie would be useful, should i require.This is mad. I can't see that sprocket set up lasting more than five minutes.
Hark! Updates!
Finishing off the centre driveshaft was a f
king heap of fking What constantly surprises me with machining is how much time goes into setting up the part you are cutting in the mill, vs actually cutting the thing. Setup time on this part was 4 hours which included buying, modding and generally persuading into use a rotary table (that looks very homemade, thanks ebay). This was a couple of hundred quid - but i feel justified in not including this in the build cost because its a useful tool for loads of metalbashing jobs and ive always wanted one!
Im centering the shaft in the independent 4 jaw rotary table in this shot, in order to cut splines in the shaft. Except noone in their right mind would ever get and endmill near that diameter, the stickout is silly. Cutting a spline on this would be like trying to shorten a diving board with a pole mounted chainsaw. I had to build a steady, at exactly (no such thing in the metalbashing world) the same height as the rotary table centreline.
As i said - all in the setup.
To cut the splines i used this 45 degree tipped endmill. (which happens in this photo to have a chunk taken out of it, but luckily my camera forgot its reading glasses so you can't see that). The female spline in the inner CV joint seems to have a nearly 90deg V to the spline so this will do. Good enough for who its for.
Horrendous i think you'll agree. I am not a machinist, i just pretend. To mill this i moved the bit down the shaft, back, and rotated the table 20 degrees (because 18 spline shaft). Took 2 rotations to get to depth.
To finish this off, i cut 2 keyways (180 deg apart) in the centreshaft and broached a couple of respective keyways through the sprocket carrier and shaft collars. Turn the mig to 11, dollop on the weld.
Fits! (unwelded unbroached continuity error, noone will notice promise)
Im somewhat concerned about the strength of the splines - this is just unhardened mild steel, without any of the clever flavourings that car manufactures spec for the material to improve strength/hardness/ductility/cost/sex appeal. But that said we are only dealing with a double digit hp and skinny decade old tyres. I think ill chance it.
I couldnt resist mocking the engine back up and seeing where that got us...
So far so good....
The exhaust fits (will need to be snaked through whatever structure i build to hold the drivetrain in) but the rest looks all a bit cosy. You can see the carbs arent going to fit - the scuttle is in the way. At this point the way i see it the options are either move the engine (to where?) or perhaps the intake manifold can be flipped over to bring the carbs to somewhere under the windscreen. This will probably wreck the intake flow path and i've no idea if these carbs are directional (its a bike, surely they can deal with a bit of fuel slosh in the bowls ect). To be considered another time.
Theres also this issue to ignore:
Update enough for now - more progress soon.
Finishing off the centre driveshaft was a f
king heap of fking What constantly surprises me with machining is how much time goes into setting up the part you are cutting in the mill, vs actually cutting the thing. Setup time on this part was 4 hours which included buying, modding and generally persuading into use a rotary table (that looks very homemade, thanks ebay). This was a couple of hundred quid - but i feel justified in not including this in the build cost because its a useful tool for loads of metalbashing jobs and ive always wanted one!Im centering the shaft in the independent 4 jaw rotary table in this shot, in order to cut splines in the shaft. Except noone in their right mind would ever get and endmill near that diameter, the stickout is silly. Cutting a spline on this would be like trying to shorten a diving board with a pole mounted chainsaw. I had to build a steady, at exactly (no such thing in the metalbashing world) the same height as the rotary table centreline.
As i said - all in the setup.
To cut the splines i used this 45 degree tipped endmill. (which happens in this photo to have a chunk taken out of it, but luckily my camera forgot its reading glasses so you can't see that). The female spline in the inner CV joint seems to have a nearly 90deg V to the spline so this will do. Good enough for who its for.
Horrendous i think you'll agree. I am not a machinist, i just pretend. To mill this i moved the bit down the shaft, back, and rotated the table 20 degrees (because 18 spline shaft). Took 2 rotations to get to depth.
To finish this off, i cut 2 keyways (180 deg apart) in the centreshaft and broached a couple of respective keyways through the sprocket carrier and shaft collars. Turn the mig to 11, dollop on the weld.
Fits! (unwelded unbroached continuity error, noone will notice promise)
Im somewhat concerned about the strength of the splines - this is just unhardened mild steel, without any of the clever flavourings that car manufactures spec for the material to improve strength/hardness/ductility/cost/sex appeal. But that said we are only dealing with a double digit hp and skinny decade old tyres. I think ill chance it.
I couldnt resist mocking the engine back up and seeing where that got us...
So far so good....
The exhaust fits (will need to be snaked through whatever structure i build to hold the drivetrain in) but the rest looks all a bit cosy. You can see the carbs arent going to fit - the scuttle is in the way. At this point the way i see it the options are either move the engine (to where?) or perhaps the intake manifold can be flipped over to bring the carbs to somewhere under the windscreen. This will probably wreck the intake flow path and i've no idea if these carbs are directional (its a bike, surely they can deal with a bit of fuel slosh in the bowls ect). To be considered another time.
Theres also this issue to ignore:
Update enough for now - more progress soon.
Edited by sparkybean on Saturday 18th January 20:08
eliot said:
So you don’t intend to fit a diff?
I think its a bit late for that! Honestly i didnt want the extra engineering effort or significant added cost of buying an off-the-shelf unit.http://racetrackdriving.com/tech/fwd-welded-diff/
TLDR: Power oversteer in a front wheel drive (if it doesn't roll first), says this man.
If you are expecting a build with a refined smooth tuned handling setup, then i think youre going to be dissapointed!
You may get some assistance/advice from Sparrow
http://www.sparrowautomotive.co.uk/citroen2cvbmw.h...
http://www.sparrowautomotive.co.uk/citroen2cvbmw.h...
sparkybean said:
http://racetrackdriving.com/tech/fwd-welded-diff/
TLDR: Power oversteer in a front wheel drive (if it doesn't roll first), says this man.
!
I think you are reading the bits that suit you. He goes on to say that low speed manoeuvring around the paddock is horrible. TLDR: Power oversteer in a front wheel drive (if it doesn't roll first), says this man.
!
article said:
You pay a price for the awesomeness that the welded differential is, and that price is paddock maneuvering.
At something like 90 degrees of steering angle, while driving at 5 mph or so the car unmistakenly informs you that the left and right wheels want to travel different distances, but cannot. Once the tires start jumping in tight corners I do not add any further steering angle or speed. Supposedly these low speed maneuvers are what destroys axles.
I make a lot of 3 point turns in the paddock with this car, and strategically select my routes into and out of my garage/parking spot
!
At something like 90 degrees of steering angle, while driving at 5 mph or so the car unmistakenly informs you that the left and right wheels want to travel different distances, but cannot. Once the tires start jumping in tight corners I do not add any further steering angle or speed. Supposedly these low speed maneuvers are what destroys axles.
I make a lot of 3 point turns in the paddock with this car, and strategically select my routes into and out of my garage/parking spot
!
I did read that yes. I fully accept that slow speed manouvering will be horrible.
High speed manouvering will also be horrible, as well as medium speed manouvering.
In fact even in a straight line, without the manouvering, it will be horrible. Actually even stood still, not sat in it, not looking at it, it is horrible. No normal person in their right mind would ever want this. This is automotive build equivilant of a stpost and i am having a hilarious time of it.
This is not your airconditioned M5 (clearly)
Maybe i should start taking bets for 'distance until mechanical failure'
So far i have had;
Instantly
5 minutes
As soon as you turn away from dead ahead
Any raises? Can i get an hour out of it?
High speed manouvering will also be horrible, as well as medium speed manouvering.
In fact even in a straight line, without the manouvering, it will be horrible. Actually even stood still, not sat in it, not looking at it, it is horrible. No normal person in their right mind would ever want this. This is automotive build equivilant of a s
tpost and i am having a hilarious time of it.This is not your airconditioned M5 (clearly)
Maybe i should start taking bets for 'distance until mechanical failure'
So far i have had;
Instantly
5 minutes
As soon as you turn away from dead ahead
Any raises? Can i get an hour out of it?
Edited by sparkybean on Monday 13th January 10:19
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