Forced induction 100cc

[ducatilover]

I like the new idea a lot, that wee bugger Husaberg posted is a very neat bit of kit

I may be able to help source RHB31 bits, I know a chap, or two
There are a few alternatives for that size, but the 31 is probably the most common thing you'll find and they flow about as well as you can manage out the box.

[Sketchy_Racer]

You do know RHB31s spin up to about 170,000rpm when they are working, or something silly like that.

Yep, that is the exciting part! I will most likely not have to get impeller RPM up to that point as the little 100cc motor is right on the surge line of the compressor. I still need to learn weather surge is going to be such an issue on a mechanically driven compressor wheel as surge is what happens to a turbo when the exhaust pressure is no longer enough to over come the generated intake pressure. Being mechanically driven makes me think that I will get away with being so close to the surge line.

A little inspiration not that you need it. http://www.sherline.com/cncproj.htm



i would have said 200000..........
i think i have a compressor map somewhere for the IHI's.

Thanks for that link, I have seen these on other websites where people had fitted them up to bikes, and unfortunately they don't work, well at least not in the applications I have seen where they tried to run them without a plenum. Beautiful piece of machining though! I am going the cheats way and using pre developed parts to save me time, the gearbox is going to be easy too.

[Ocean1]

the gearbox is going to be easy too.

Epicyclic unit out of an air tool?

[Sketchy_Racer]

Time to update a little.

I really haven't spent anytime on the supercharger bike since I got it running. I did 4 dyno runs with it after sorting power supply issues and managed to get a whopping 12HP out of it (running like a bag of spanners) however the dyno runs were more to test the charger performance not the motor and didn't really do any tuning with it, but the roots style supercharger just sucks balls. I have learnt I was excessively optimistic with the efficiency I was hoping to achive and the boost levels are much lower than planned and I don't want to increase the supercharger RPM as it will pre heat the intake charge even more.

So, in between work and holidays, I have been working on a gearbox layout a 1:10 + ratio which will help me achieve the RPM required for a RHB31 turbo impeller.

There is nothing new about this concept, it's called a traction drive planetary gearbox which is well suited to high speed applications. Rotrex use them in their superchargers which are really really nice units.

The only pain in the ass part about the layout is that I have to run a set of gears on the input to get the rotation the right way as the motor spins the wrong way for the turbine. (once it's gone through the gearbox.

Anyway here are a couple of screen shots from the solidworks assembly, I will make an exploded view at some point and explain to those interested how it all works.



Cheers,

-Sketchy

[crazy man]

do you want a Rotrex houseing. l have a pile of them...ps kenny said he will teach you how to make one

[Kickaha]

So, in between work and holidays, I have been working on a gearbox layout a 1:10 + ratio which will help me achieve the RPM required for a RHB31 turbo impeller.

Why not put a pulley on the exhaust side instead of an impeller and drive it off the engine?

[Sketchy_Racer]

I'm guessing you're taking the piss Kick,

but just in case; I wont achieve 100,000 RPM plus with belt drives and the center housing of the turbo wont support lateral loading from a belt.

It's either gears or a jack shaft and turn the charger around in the chassis to get it work, and I dont want two belts in there, one is enough.

[Kickaha]

I'm guessing you're taking the piss Kick,

no but I hadn't thought about how fast you'd have to spin it, seen some like that on car sites

[Sketchy_Racer]

do you want a Rotrex houseing. l have a pile of them...ps kenny said he will teach you how to make one

Yeah mate, I would love to take a look at one.

Haha I would love to see ken's design he's much better on solidworks than i am but not as much hands on experience

[Sketchy_Racer]

no but I hadn't thought about how fast you'd have to spin it, seen some like that on car sites

Ah yeah, the big compressors are ok to do that with but not this little baby.

[crazy man]

Yeah mate, I would love to take a look at one.

Haha I would love to see ken's design he's much better on solidworks than i am but not as much hands on experience

will post a pic of what l have . looks like a turbo housing; have about 10 of them . so you worked out who ken is(-;

[husaberg]

Its a shame that you have given up on the rootes......the HP you were getting 12hp i think (is possibly twice that of the std pitbike anyway) did you dyno it first? i also assume it was without a inter-cooler as well?
I see it as the second best compromise.(The best for tight circuit racing being being screw...imo)
i see an issue with the power delivery with the centrifugal charger.....yes even with flirting with the surge line and mega drive speeds needed to obtain boost.(unless the drive can limit and maintain speed independent of the engine speed which maybe your drive can i can remember some one posting the the oil squeezed drive details on the ESE site i think maybe it can)
I know there will be suitable size screw compressor wheels.( lurking in commercial air cons) Also there is some interesting Wankel style rotary air con compressors for car aircons.
That said I certainly don't have anywhere near 1/1000's of your ability you possess to do scratch built housing or the rootes blower you did.

Maybe it your rootes could be tried on the Speedpro engine?

[Sketchy_Racer]

Its a shame that you have given up on the rootes......the HP you were getting 12hp i think (is possibly twice that of the std pitbike anyway) did you dyno it first? i also assume it was without a inter-cooler as well?
I see it as the second best compromise.(The best for tight circuit racing being being screw...imo)
i see an issue with the power delivery with the centrifugal charger.....yes even with flirting with the surge line and mega drive speeds needed to obtain boost.(unless the drive can limit and maintain speed independent of the engine speed which maybe your drive can i can remember some one posting the the oil squeezed drive details on the ESE site i think maybe it can)
I know there will be suitable size screw compressor wheels.( lurking in commercial air cons) Also there is some interesting Wankel style rotary air con compressors for car aircons.
That said I certainly don't have anywhere near 1/1000's of your ability you possess to do scratch built housing or the rootes blower you did.

Maybe it your rootes could be tried on the Speedpro engine?

First dyno run was about 6hp from memory, then I made up the rest with just adjusting the fuel trim on the map which improved peak HP but hurt lower rpm.

The boost characteristics from a roots is far more desirable than the centrifugal but the efficiency is terrible and with such a small motor I can't afford the parasitic losses.

From what I can figure, I will be able to over drive the centrifugal charger so that it makes excess boost pressure then bleed it off when the RPM comes up and still have less parasitic loss than the roots with about a 40 degree cooler intake charge temp.

Failing that, I have some really cool ideas on making an electronically controlled CVT but I will get the supercharger working before I waste my time with any of that.

The roots works well, it just needs some time and experimenting with rotors and the housing geometry. I never did try the 3 lobe rotors but it would be interesting to see how that works. If Mike is keen I will send it up for him to have a play with it but I'm hoping he will turbo his one.

[husaberg]

First dyno run was about 6hp from memory, then I made up the rest with just adjusting the fuel trim on the map which improved peak HP but hurt lower rpm.

The boost characteristics from a roots is far more desirable than the centrifugal but the efficiency is terrible and with such a small motor I can't afford the parasitic losses.

From what I can figure, I will be able to over drive the centrifugal charger so that it makes excess boost pressure then bleed it off when the RPM comes up and still have less parasitic loss than the roots with about a 40 degree cooler intake charge temp.

Failing that, I have some really cool ideas on making an electronically controlled CVT but I will get the supercharger working before I waste my time with any of that.

The roots works well, it just needs some time and experimenting with rotors and the housing geometry. I never did try the 3 lobe rotors but it would be interesting to see how that works. If Mike is keen I will send it up for him to have a play with it but I'm hoping he will turbo his one.

yeah re the drive i was think like the electric clutch on some fans and the 4ag supercharged engine i think the super turbo March also had something tricky.
Out of interest what psi were you getting with the 120?cc engine?.

i seem remember the fuel map for a twin (i think this came from the CHCH turbo Norton i posted with a link ecu) is way more complex than a 4 so i guess the single would be even more so .

[Ocean1]

Failing that, I have some really cool ideas on making an electronically controlled CVT

Sounds heavy. What's the hp requirement for the blower drive? How does a suitable AC generator/AC motor drive compare for mass? You'd get to accurately and easilly define motor/blower revs. Including on the fly, during a race. You also get to mount the blower wherever you want.

Can you organise an extra output from an ECU to control an AC drive?