Forced induction 100cc

[Sketchy_Racer]

Okay, so I was going to keep this quiet incase it turned into an epic fail, but i figured some of the jokers out there may find some interest into this.

I decided a while back that I quite like the idea of forced induction, I built a 250cc turbo bike as a bit of a laugh and it's great fun however not really suitable power for anything at all and as you could imagine trying to turbo a bike half the size wouldn't really work that well.

So the next option is supercharging. Sounds like a great idea until you work out that the smallest supercharger is still far to big for a 100cc motor, it would make boost however I believe that it may still draw so much energy to power the over sized super charger that the gains would be offset. I thought that it would be possible to build a small supercharger so I went about designing one in solid works.

I designed two different styles, both roots style supercharger but one with a two lobe rotor and one with 3 lobe. The two lobe rotor was much harder to draw because they rely on cycloid curves:

http://en.wikipedia.org/wiki/File:Cycloid_f.gif

They are simple by nature but making them in solidworks is a little more involved as they need a parametric equation to create them

http://en.wikipedia.org/wiki/Hypocycloid

Once the math is done it was pretty straight forward though


Next was the motor to use, this was pretty easy as the cost and avaliability of parts were the main goal for me, I purchased a 125cc Lifan engine for $350.00

Before the haters get going, I have also ordered a sleeve kit for it to drop it to 100cc

http://www.akunar.com/CYLINDER_SLEEVES.htm

They are a simple motor and before it ever gets run it will be getting replacement bearings but I am happy with the weight of it and also the design, it looks like it will work ok (and a new head assembly is only $60 and piston kit is $20 !!!)

The horizontal motor works great in the chassis for two reason, one being that it keeps the COG nice and low which is often over looked in a bucket and also it gives me much more space to work with above the engine for a supercharger and intercooler.

My supercharger is just a baby, and I want it that way a large focus on the build is trying to keep the rotational mass as low as possible as well as keeping my drive losses to a minimum.

The assembly weight will be touch over 3kg for the supercharger which I am happy with, I may lighten it a bit more with some heat finning which will also help reduce intake air temp.

That's about it for now and here's some pictures as they say a thousand words.

Cheers,

-Sketchy

[bogan]

I'm not a bucketeer, but it is cool to see what you fullas come up with! Good onya for giving it a hoon

That thing is tiny! How were the lobes made? Whats the clearance like? Guess if it spins fast enough it might reduce the amount of 'blowback', one of those back of the mind project ideas I had myself, so hopefully yours will work and give me motivation...

[richban]

Nice work. I'll take one thanks. Just so happens I have an FXR engine that needs a rebuild.

[Kickaha]

The horizontal motor works great in the chassis for two reason, one being that it keeps the COG nice and low which is often over looked in a bucket and also it gives me much more space to work with above the engine for a supercharger and intercooler.

There is another one being built using a similar motor for the same reasons

[Sketchy_Racer]

I'm not a bucketeer, but it is cool to see what you fullas come up with! Good onya for giving it a hoon

That thing is tiny! How were the lobes made? Whats the clearance like? Guess if it spins fast enough it might reduce the amount of 'blowback', one of those back of the mind project ideas I had myself, so hopefully yours will work and give me motivation...

Yep it's tiny alright, the rotors weigh 80 grams each

They were made in CNC mill

http://westurn.com.au/wp-content/upl...05/mb-56va.jpg

Tooks 10 minutes to mill each rotor but was taking it easy with the finishng cuts as size is quite important.

The rotors will have .05mm clearance between each other and .03 on the outer housing.

[Pumba]

Very very cool

[Henk]

Sweet. Do this thing, if for no other reason than because you can.

[koba]

That is sobloodycool.

[koba]

so I was going to keep this quiet incase it turned into an epic fail

Getting it that far is a win in my books.

[gav]

Have you considered just fitting an 80cc MX motor instead? I'm sure no one would mind .....













But that looks bloody nice! Good work Glen.

[Grumph]

Nice work, the Martin blowers which were made in ChCh used an extrusion for the rotors. Cost the original maker a bloody fortune as Comalco insisted he pay for the dies.....However once done production is much more viable as you can make blowers in a range of lengths with the same rotor profile.
3 Lobe....all the info I've ever seen suggests that the 3 lobe layout suits relatively low rpm use. The guy who was responsible for the final versions of the Martin blower did quite a lot of flow work and bench measuring of efficiency and came up with a guide bar across entry and exit openings which reduced churning and let the 2 lobe design work up to over 10 grand. This was important when you put a small blower on a biggish road car motor as it has to be run at higher than engine speed.
Now the fun bit - how are you driving it - and what fuel metering ? Carb (laughs out loud) or injection ?

There's a neat trick to take drive off a plain shaft without keys or splines if you need to know.
Clearances worry me a tad - even in smal sizes the rotors will expand - end clearance is particularly sensitive. Be generous.

[speedpro]

I'm sure one of the supercharged singles from the early days used a similar style Honda engine and the supercharger was a modified VC160 lawnmower engine sucking through a reed valve and carb. The same guy, Neil Hintz, built another one with a shortened roots type blower. He also built a rotary vane compressor mounted direct to the crank of a CB100 style Honda. Shock loads in the drive was always a problem as I understand.

Agree with the comments about allowing clearance. If you have any doubts blow warm/hot air through it to warm the rotors and try turning it. On drag race motors they have a bit of clearance but use teflon lip seals. The good ones I've seen are magnesium though so not sure about expansion etc compared to alloy.

I'm thinking of carrying on with mine. I really should put the MB engine in the RS chassis leaving the FZR chassis with nothing in it.

[Buckets4Me]

now this is talking and in the spirit of bucket racing

if you FAIL !!!! we will all have a laugh (with you not at you)

and if you succed good we all want you to

just makesure the pictures keep coming
and go check out the E.S.E thread they talked about how to turn the suppercharger over without robbing power from the motor just dont tell anyone till you have run it like that

[Sketchy_Racer]

Nice work, the Martin blowers which were made in ChCh used an extrusion for the rotors. Cost the original maker a bloody fortune as Comalco insisted he pay for the dies.....However once done production is much more viable as you can make blowers in a range of lengths with the same rotor profile.
3 Lobe....all the info I've ever seen suggests that the 3 lobe layout suits relatively low rpm use. The guy who was responsible for the final versions of the Martin blower did quite a lot of flow work and bench measuring of efficiency and came up with a guide bar across entry and exit openings which reduced churning and let the 2 lobe design work up to over 10 grand. This was important when you put a small blower on a biggish road car motor as it has to be run at higher than engine speed.
Now the fun bit - how are you driving it - and what fuel metering ? Carb (laughs out loud) or injection ?

There's a neat trick to take drive off a plain shaft without keys or splines if you need to know.
Clearances worry me a tad - even in smal sizes the rotors will expand - end clearance is particularly sensitive. Be generous.

Interesting about the extruded parts, I would have though it would take a lot of production to weigh up the cost of getting a die made, especially when the rotors are such easy parts to make.

I went the three lobe as because I had read the same as you regarding lower RPM use, I would like to keep RPM as low as possible to try reduce heat and also again try keep the rotating mass under control.

I am planning on running a carb with a draw through system, much like this guy

http://www.youtube.com/watch?v=tCURXinXoEg

It seems to work well for him so I am hoping it will work well for me also. I may look into fuel injection later on but at the moment I am sure I will have enough little bugs to work out with the supercharger and motor.

I am going to be running an ignitec on it as I need a rev limiter and also will need a boost compensated curve on it.

Regarding clearances, what would you recommend?

I have based my numbers about the thermal expansion of 6061 T3 alloy which is; 23 microns, per meter per 1 degree celcius and then a fudge factor for rotational stretch.

I want it to be as efficient as possible so was also going to try running a small amount of two stroke premix in the fuel (as it will be draw through) to keep the rotors sealed and lubed if there are any points of contact.

Any thoughts, and yes I am very interesting in your shaft locking method. I was looking at making a gear with a tapered ID with a taper ring that gets clamped in there but would like to know how others have successfully done it.

Check out this video at around 1:20 mark, it uses the same idea

http://www.youtube.com/watch?feature...&v=m-ZWPnvC0wc

Cheers

-Sketchy

[Henk]

Neat project.
Regarding the cost of dies etc, for big runs extruding would still be the way to cost wise but for small runs or one offs CNC is the ticket. Solid works and the wide availability of CNC machines have been a real game changer for this sort of thing as evidenced by the amount of billet bling available these days at what is really super cheap prices.