Donor Gearboxes

[el chupacabra]

That’s good to know about the KTM cranks, it’s a pity aliexpress don’t sell 85sx cranks. They do sell cylinders though, minus the power valves, hopefully the lack of a power valve on the yz don’t make it too much of a handful.

[husaberg]

This was a homebuilt 100cc twin based on the Aprilia Rotax v twin.


if you are set on the YZ stuff you can make up atac valves


https://www.kiwibiker.co.nz/forums/a...6&d=1420439042

[F5 Dave]

So if we could just group up about thirty of those in a row. . .

[el chupacabra]

Now that 10cc motor scaled up to 100cc would be a neat idea using some good bucket legal cylinders and an mx85 gearbox or the like.

I've though about using ATAC chambers on the rear cylinders to start with obviously later on once it is running. As the cylinders fire in pairs the chamber can probably be shared.

[F5 Dave]

Picking up some old RG50 cases sometime back I did consider a Vtwin conversion. But I'm done racing for now, no point getting more projects beyond what I'm going to ride myself.

[husaberg]

Now that 10cc motor scaled up to 100cc would be a neat idea using some good bucket legal cylinders and an mx85 gearbox or the like.

I've though about using ATAC chambers on the rear cylinders to start with obviously later on once it is running. As the cylinders fire in pairs the chamber can probably be shared.

It was a 100cc i just ran out of ink.

[el chupacabra]

I was going to say the cylinders looked a bit too detailed. Its looks like a PLA 3D print more so than aluminium.

Here's an update after removing a heap of material. Luckily I will be lost-foam casting and won't need any cores.

Also, It appears that the lower crank will push oil around probably foaming it up quite a bit, I will probably make the sump slightly deeper so the oil pump can pick it up and spray it around. . . or just see what happens.

The cases alone would weigh 24kg, time to cut even more weight. 7kg is what the upper cylinder part weighs.

[el chupacabra]

Major cock up . . . I forgot how big the clutch is . . . Oh well, time to rotate the lot forward and lift up the lay shaft, there is a good 4-5 hours down the drain.

At least I haven't made any parts yet.

[husaberg]

Major cock up . . . I forgot how big the clutch is . . . Oh well, time to rotate the lot forward and lift up the lay shaft, there is a good 4-5 hours down the drain.

At least I haven't made any parts yet.

Are you going to 3d print it in plastic minus as a test like these ones?
i was thinking he was going to 3d printed in alloy but He eventually CNC'd them in Alloy.
for the first one it might be a good option to as you will not need to remove so much metal afterwards and you can add in gussets etc.
but it would be good to print it 3d print minus 5% to put it in your hand so actually see. Well thats how my brain works anyway.


On trick i learned from somewhere was to have a separate oil for clutch and Gearbox as you can then run two levels but i guess with a spay bar that will not be needed.

[el chupacabra]

I will print it and look at it all. Then I will use a cnc router and make it out of 4-5 layers of high density polystyrene all glued together, making it easy to machine all the over hangs.

I was up thinking about it last night, how the clutch will hit the RHS upper crank wheel. I will just translate the cassette to the right 15mm and make the layshaft a little longer problem solved.

[Grumph]

If you're going to the trouble of making a longer Layshaft, the alternative is a longer mainshaft and a dry clutch....

[husaberg]

I will print it and look at it all. Then I will use a cnc router and make it out of 4-5 layers of high density polystyrene all glued together, making it easy to machine all the over hangs.

I was up thinking about it last night, how the clutch will hit the RHS upper crank wheel. I will just translate the cassette to the right 15mm and make the layshaft a little longer problem solved.

You can extend the shafts its pretty common TZ has done it on the ESE thread and the Barry Hart Sparton had extensions welded on to fit TZ clutches. As the Sparton place was the forerunner i think to Dyson/Nova they had all the equipment to make their own gears and shafts yet they chose to just weld on bits.

[jato]

sorry to hear about the set back - considering the constant effort by the designer to be saving weight is it possible to use a smaller (lighter) clutch and not shuffle / enlarge the layout? assuming the clutch is running at 40% of engine speed or so it won't have so much torque to deal with. I notice the RMZ250 clutches piled under the bench here are 8 plate and measure 148mm OD. easy to make a gear for them too with their rubber dampers. also easyish to spline the hub to suit the triumph shaft. another 5 cent thought - how does the tyre width/chain/front sprocket/geabox to crank centres look ?

[el chupacabra]

I’ll get some dimensions when I slave away tonight. The clutch gear currently is 178mm. Overall It is currently smaller than the original triumph engine funnily enough. It might be 50mm longer to the lower spark plug. I think I can make it work without too much of a redisgn. I could Run the magneto on the RHS if I’m worried about total width. I’ll measure it up but it’ll only be 20-25mm wider at the most.

[el chupacabra]

I could just offset the upper cylinders too, it’ll make carb mounting more direct. But reeks of effort, I’ll see how much is involved when I get a chance to jump on the PC.

Future me will model the clutch gear so I can see it while designing haha.