Donor Gearboxes

[el chupacabra]

Here's a picture for a sense of scale, I'm going to see how it compares with my Banshee motor, RGV motor and RSV1000 motor before carrying on in case it is too long to accommodate.

I'll need to order the cylinder and crank soon if it looks like it'll fit in a bike.

Also it looks like I will need to remove a lot of mass from the gears as they could make the whole rotating assembly quite heavy.

[husaberg]

I am sure you have consdered this but you can shorten the engine by opening the v making it taller the NSR was about 113 degrees. okay 112

You can get the rear yzr500 dimensions by scaling off the wheel rim.

You could also bring the the gearbox closer by driving the clutch off one the outer cranks
But having the extra room allows space to watercool the cases.

You could also bring the gearbox countershaft forward about 20 degrees by tilting it forward which will shorted the length to the countershaft

[el chupacabra]

I have been contemplating using a direct crank to clutch setup but it’ll be a disaster with the 85cc cranks. Using a stroked Banshee crank and making a large V twin popped into mind but that wasn’t the point of the project. . . Hmmm V3 using 1.5 banshee cranks joined together and sx150 cylinders. . . Seeing that BSL 500 on the weekend was pretty neat and got me thinking.

But then It has to be a V4. So much more appeal tiny little pipes and cheap parts.

The Banshee engine and RSV1000 engine are about the same length. The only thing is it might be a bit tight in an RGV250 chassis as the spars are only approx 240ish mm apart. So I don’t think the length or height will be a problem. I still might open up the V angle too, although I am worried about the balance if I do so.

[jato]

The cranks and layshaft look compact - the rest of it not so much...what is the layshaft to clutch center distance ( and gear sizes)? how many main bearings? I recall the RGB 500 gearbox was extensively drilled for lightness (even the gear dogs had about a 2.5mm hole right down the middle of them) selector drum looked like a bit of cheese. and they were bullet proof too. lightening a gearbox that has already been heat treated would be do-able but an extremely slow and expensive process - the carbide drill might only handle 2 holes before its toast. ponder ponder

[husaberg]

The cranks and layshaft look compact - the rest of it not so much...what is the layshaft to clutch center distance ( and gear sizes)? how many main bearings? I recall the RGB 500 gearbox was extensively drilled for lightness (even the gear dogs had about a 2.5mm hole right down the middle of them) selector drum looked like a bit of cheese. and they were bullet proof too. lightening a gearbox that has already been heat treated would be do-able but an extremely slow and expensive process - the carbide drill might only handle 2 holes before its toast. ponder ponder

You could do some complex math on the balance,
but as the Yamahas were often at 70 degrees which is 20 less than ideal at 110 that's the amount same less than ideal only in the opposite direction.
Your gears can incorporate a balance shaft as well.


Also that Aprilia is at 60 and so was the Bitten.

[el chupacabra]

113mm off the top of my head. Clutch centre to layshaft.

I considered running the layshaft lower and having the lower crank in front and the upper above the layshaft. I think this might be an issue with intake angles being too sharp though turning through extreme angles.

i have decided all of the gears I am getting manufactured will look like Swiss cheese haha.

[jato]

sketches-with-maths that i've done show that with twin cranks spinning the same direction you can have any vee angle you like but you have to time them to keep the residual imbalance of for example the top left cylinder constantly opposing the residual imbalance of the bottom left cylinder. no balance shaft needed and no rocking couple either . i'm 90% sure of the sketch. with little cylinders i believe you can get away with a bit but when/if you go to say a 250 cylinder you have to get the balance pretty well spot on

[el chupacabra]

At least how I plan on putting it together I”ll be able to change the firing order by taking out the balance shaft and rotating the cranks. So changing it up won’t be a hassle.

I”ll do another layout tonight with the lay shaft lower down and I’ll see what the intake angles look like.
But otherwise I’m happy with the current layout. It leaves a lot of room for the oil and coolant pumps.

[el chupacabra]

I love how quickly you can change things in CAD, here I have rotated the cassette 10 degrees CCW and lowered and rotated the crank 35 degrees CCW it definitely looks a bit more compact.

[el chupacabra]

Here I’m after some advice as I’m thinking do I run a mechanically driven coolant pump from a gsxr600 or something similar. . . Or could I run an electric pump moving around 20-30l a minute, I seem to recall something mentioned about 1l per min per hp but I’m unsure if that is necessary.

Also I’m thinking about a small electric pump for the gearbox oil as it will speed up the design process immensely.

Let me know your thoughts or any experiences you’ve had.

[husaberg]

Here I’m after some advice as I’m thinking do I run a mechanically driven coolant pump from a gsxr600 or something similar. . . Or could I run an electric pump moving around 20-30l a minute, I seem to recall something mentioned about 1l per min per hp but I’m unsure if that is necessary.

Also I’m thinking about a small electric pump for the gearbox oil as it will speed up the design process immensely.

Let me know your thoughts or any experiences you’ve had.

Very few pumps are available that flow enough water and don't suck too many amps.
https://daviescraig.com.au/electric-water-pumps
7-10 amps needed


Kubota's have a neat little alternation with plenty of juice they are used on a lot of classic bikes.
https://www.as-parts.nz/product/1743350


if you were heading the electric route
Look at pumps from EV or Hybids. or V8's like craig Davis.
That HP/h20 was based on GP experience i guess if you are 300HP a liter rather than 400/litre you could drop it the same amount % wise
You can also belt drive the pump with a toothed belt but whatever you do mount it as low as possible.
You can drive this of the ignition shaft or even off the end of the rotor like a KTM50.

[jato]

only 2 cents worth of info but way back when the first watercooled rm125 came out 2 of us did some very crude observations and concluded there was an astounding waterflow for a puny little 125 - some thing like a healthy garden hose on half blast (or more) at full revs. maybe only 1 cents worth of info....

[el chupacabra]

Not a bad idea driving it off the crank end. Or even the layshaft. . . Or on the clutch cover using Yamaha banshee parts. Maybe the electric route is not really any simpler and won’t provide enough flow.

[F5 Dave]

I tried cheap pumps on my approaching 30hp bucket and eventually bought a decent arrangement which was an intercooler booster pump for some American car off ebay. Too long ago to be in my history. Was entirely adequate for the purpose and lives on 6 years after I sold the bike.

Ran off a CR250 8 pole stator and drove an Ignitech, shift light, det counter, shifter as well and voltage would not drop at all during all gears run on dyno.

Could be a bit meagre for 4 cylinders. But gives you an idea of what a decent stator can cope with.

[jato]

weight saving is always on offer if you can get one part to do more than one job - if you were to use something like a yz250f oil pump https://pronorthparts.co.nz/engine/o...s-idler-gears/ and drive it of the back of the clutch then you could make a longer oil pump shaft and use that to drive the (gsxr 600?) water pump. the water pumps i've looked at all turn the same direction as the wheels and turn around 60 ish % of engine speed - the lay shaft may or not be suitable. the oil pump drive gears i've looked at so far have all been std module 2 so easy to fashion up a gear train if needed.