The ULTIMATE 2-stroke bike engine

[Grumph]

Yeah they do. But when you snap the throttle off they slow down fast due to heaps of drag on the show. Bikes will keep on rolling. And like I said you would need some very modular rear breaking to turn it in like a conventional gear boxed bike. Especially if it was a 200hp 500. Rolling into a corner at 260 with just that rear break to get it turned would be interesting.

CVT would be great if building a drag bike.

Yeah, well slipper clutches are part and parcel of the drag world...For those interested in the CVT/racebike concept, google Monotrack Experimental and have a look - it's been done. From what i read elsewhere the stall speed of the cvt was high enough that in theory you'd never drop out of the power band. Think of it as a single gear with an automatically slipped clutch....
Like a lot of belt drives I understand it was let down by a lack of alternative ratios.
A combination of a cvt primary drive with a 3 or 4 speed dog box may work - but this is only an elaboration of the Chapparal CanAm car's "auto box" which was a torque converter driving a 2 speed dog box. This worked great in a light car with enormous torque....

[speedpro]

I've changed the final drive ratio on my scooter. The only time it's noticeable is where it used to top out at 105kmh it now goes off the clock plus a bit more. The roller weights working against the spring determine engine revs at any throttle position. Throttling off does result in the CVT immediately going to the highest gear ratio possible and therefore not much engine braking happening.

[speedpro]

More thought has been wasted on this. I've been thinking that regular port and ducts are all designed due to limitations caused by being fed from below the piston and the limitations of an air cooled barrel requiring the single exhaust duct to be at the front for cooling. The switch to water cooling was only taken advantage of by an extension of the power gained and by relocating the exhaust duct to another position other than the front. Designers stuck with the single exhaust duct on one side due to the scavenge pattern. If they'd thought about it and changed the scavenge pattern they could have utilised more exhaust ports/ducts.
Frits' FOS cylinder takes advantage of water cooling by having exhaust ports wherever he wanted them. Only made possible by his new scavenge pattern. Those 6 transfer ports could just as easily be fed by a circular plenum in turn fed by a supercharger. The truck engines have a similar arrangement but with poppet valves in the head, and a four stroke bottom end. For a
180-degree-firing-order V-twin with a shared crankcase you could run a regular 2-stroke bottom end.
The question for Frits is how well do his cylinders work? I can see the central column being formed by the intake streams but have difficulty seeing how the flow continues out the exhaust ports and doesn't form a circular rotating column - up the centre, out across the head, down the cylinder wall, to blend with the incoming streams and go round again.
Also in normally aspirated form I'd imagine all the time area values would be similar to regular cylinders but with big advantages in the port layouts to achieve it. Is there a way to determine requirements if the engine is supercharged or would it be a case of suck it and see?

[Tard]

Jeez, I hope F5 Dave's alright...

[Spearfish]

Jeez, I hope F5 Dave's alright...

He must be in a bad way, what ever it is.

[F5 Dave]

Well I had a bit of a hangover after wifey & I polished off some very nice wine last night, but I had a V & some cheese on toast to correct the grease imbalance that sometimes occurs and quite frankly I'm feeling pretty good now. I don't even think I'll need a kebab at lunchtime.

But thanks for thinking of me.

[avgas]

Snow mobiles do very nicely with CVT transmissions.

The first part of your sentence should tell you why. Incidentally the same reason you don't need gears on a wave runner/jetski. Traction vs Maneuverability.

Sadly unless your planning an 2-stroke drift bike, a 'chop down' is usually required every now and then.
I have used the CVT equivalent of a 'chop down' and was massively disappointed. CVT is too 'long' to for a proper 2-stroke chop-down to have any effect. Now a shot of NOS at the same time as the CVT travels down to a "faster ratio" could probably do it justice.

[Spearfish]

The first part of your sentence should tell you why. Incidentally the same reason you don't need gears on a wave runner/jetski. Traction vs Maneuverability.

Sadly unless your planning an 2-stroke drift bike, a 'chop down' is usually required every now and then.
I have used the CVT equivalent of a 'chop down' and was massively disappointed. CVT is too 'long' to for a proper 2-stroke chop-down to have any effect. Now a shot of NOS at the same time as the CVT travels down to a "faster ratio" could probably do it justice.

Has anyone ever made a manual cvt?
Instead of using weights and springs perhaps using another twist grip/rocker pedal with some sort of cam in the guts to manually move the pully up and down the ratios.

[avgas]

Has anyone ever made a manual cvt?
Instead of using weights and springs perhaps using another twist grip/rocker pedal with some sort of cam in the guts to manually move the pully up and down the ratios.

Hmmmmm would work on slow speeds. But if you want the cam to work its going to have to move at 10 times whatever the speed of the CVT pully runs at. And not only that its going to have to be all over the CVT pully.
It will look like a cone shaped tunnel boring machine when its finished.

[Yow Ling]

Has anyone ever made a manual cvt?
Instead of using weights and springs perhaps using another twist grip/rocker pedal with some sort of cam in the guts to manually move the pully up and down the ratios.

Aprillia do one on a 800cc thing, its pretend manual as there is a computer in there working the pulley to give steps. could be done with oilpressure and a feedback pot.

FWIW I quite like opposed piston 2 strokes, not like the double knocker TS3 more the Junkers type with geared cranks, really short stroke per crank , aysemetrical timing. Downside is maybe a bit tricky on petrol, but diesel is cool. Must surley be allowed 200 cc real diesel in buckets with forced scavenging as opposed to supercharging. maybe wobbly can do a Kadency pipe for the diesel

[F5 Dave]

Pity digital cameras were not popular a ways back. Mike (G) do you have any film of that Uniflow engined Bucket that was at the GP?

[speedpro]

Nope, but I've got video of it's 500cc big brother being fired up for the first time, somewhere.

[Sketchy_Racer]

Yeah they do. But when you snap the throttle off they slow down fast due to heaps of drag on the show. Bikes will keep on rolling. And like I said you would need some very modular rear breaking to turn it in like a conventional gear boxed bike. Especially if it was a 200hp 500. Rolling into a corner at 260 with just that rear break to get it turned would be interesting.

CVT would be great if building a drag bike.

For what it is worth,

On my latest GSX-R600 where we are running yoshimura engine managment, I have had the bike setup with a lot of anti engine breaking, as I hate it when I get compression lock when under hard brakes into a corner. The first time I rode it I almost ran off the track at the first turn as when you shut the throttle and expect it to slow down it damn feels like it speeds up! Just like a scooter!

However over time It has started to work very well in keeping the rear end of the bike stable under heavy braking, and I never use the rear brake, usually the rear brake does nothing as the wheel isn't touching the ground!

I would be keen on a CVT style gear system, and may even build one for the next project....

[pete376403]

Has anyone ever made a manual cvt?
Instead of using weights and springs perhaps using another twist grip/rocker pedal with some sort of cam in the guts to manually move the pully up and down the ratios.

Rudge did it back in the 1913 or thereabouts. They were banned from racing in the TT as it was deemed to give them an unfair advantage. From then on the rudge insignia was a five barred gate - playing on the barred from racing theme.

Google or Wiki "Rudge Multi"

Just about whatever you can think of has probably been done before

[speedpro]

There is some pretty high spec. CVT transmissions out there. Check these: http://www.aaenperformance.com/snow_clutch_roller.asp I'm sure they could be used on a motorcycle