Super charging gears/gearing

[hudmut]

Hi all

Can one of you help with a bit of a gearing problem. iv just made the outer casing for a super charger and need to sort a pair of gears to drive the impellers. Iv looked in to this my self but i seen to be missing some info i think i will get away with using 0.6 mod gears. My shafts are on 18mm centres and it seems that the 0.6 mod gears will fit but because of the lack of info I'm not to sure if they will mesh up right can any one say if I'm right or wrong in picking these gears.

The link is to the website is wear i was intending to get my gears from


http://www.hpcgears.com/newpdf/spurgears_0.6mod.pdf

 

[djc]

I've looked in to this my self but I seem to be missing some info. ...My shafts are on 18mm centres

You sure are missing information. What ratio do you require between the gears? Or are they the same size?

Once you know this, you have one other choice to make - the Module or size of the gears. You can have a small module with a high number of teeth ("fine" looking) or a higher module with less teeth ("coarse" looking).

Is this based on a full-sized design or is it free-form? If you could find out the number of teeth used on a full-sized or similar design, that will fill in blank and enable you to calculate what module you need.

 

[hudmut]

Yes i should of said about the ratio it does not matter to much about that as i will govern the speed of the charger from the belt drive up front the gears are just to drive the impellers at the same speed as each other nothing else.

The charger is sort of based on a full size and model at the same time but i cant get my hands on either of them any more to find out what gears are in them but i would like to go with more coarse teeth over fine.

 

[Kmot]

hudmut: Your engine looks awesome, can't wait to see the finished version!

 

[stevehuckss396]

HudMut!

If these are the gears that couple the rotors together then they must be the same tooth count. If you are stuck on 0.6 then you will need the G0.6-30's Somebody check me! We need more info!! Are you planning 2 or 3 lobe rotors? Underdrive or overdrive?

 

[steamer]

What Steve said.....
Module = Reference diameter (mm)/number of teeth

0.6 = 18mm /n > n=30

Dave

http://www.khkgears.co.jp/en/gear_technology/pdf/module.pdf

 

[djc]

...I would like to go with more coarse teeth over fine.

OK. So if they are the same ratio, you have to find a gear with a pitch circle diameter (PCD) of 18mm.

The formula for this is Module (M) = No. of teeth (N) x PCD. It has the following bounds: N must be whole number - can't have gears with half a tooth (although I've tried to make a few!). Also N must be equal or greater than 12 (smallest normal number of teeth). Finally, M needs to be a standard number - MOD 0.333 gears, for example, are not produced.

One further consideration is the the size of the shaft that goes through the gear. A larger M has relatively deeper teeth, so leaves less meat for the shaft.

Hence, we could use 12t 1.5M; 18t 1.0M; 20t 0.9M; 30t 0.6M; 36t 0.5M; 45t 0.4M; 60t 0.3M.

I think HPC have pictures of each tooth size so you can pick one that looks right. If not, let me know and I'll make a PDF of each of the sizes above for you.

 

[steamer]

....an coarser teeth will "Potentially" have more backlash....something supercharger rotors will not like much...

Good list djc.

Dave

 

[compspecial]

Looks like it could be a very powerful engine Hudmut, but being a two stroke, won't some of the charge be blown straight out of the exhaust ports by the supercharger?

 

[hudmut]

Thank you all

After reading some of the replays it looks like the 0.6 mod is the way i want to go it will all so sort of answer a few things that others have asked.

The impellers are only 2 vain iv used this over 3 because then there is less parts running so close together as well as this i don't have to run such fine teeth on the gears to drive every thing then fingers crossed the bit of backlash in the gearing is not going to up set things to much. I dont want to run to fine a teeth as iv had bad look in the past when running them at high RPM.

I'm not after high boost I'm just having ago at some thing different and this thing is never going to do much running if like all my other builds once its done in a box up it to the loft it goes.

Compspecial.

The engine is a 4 stroke 30cc OHC running 2 timing belts to each cam I'm going to run the charger of a out put shaft out the back of the crank case and that picks up on the end of the crank pin all the rods are on roller bearings as well. Iv all so got something in CAD so i can add a start motor with a one way bearing as well on there rear but ill only add that if it ever runs or before it spits its guts out.

Im sorry all if you find my stuff hard to read i do find this very hard im doing my best.

 

[MachineTom]

In a full scale supercharger (roots type) the drive gears would be helical cut. The reason for this is to provide the ability to adjust the timing (to provide clearance between the rotors) of the rotors. By shiming one gear or the other up you can adjust the needed clearance of the rotors. With straight cut gears driving the rotors the indexing of the rotors and gears would have to be dead on when cut and keyed, with no ability to adjust clearance.

 

[compspecial]

My apologies Hudmut, looking at the thumbnails I THOUGHT I saw two huge exhaust ports at the bottom of the cylinders.when i clicked and got full size i saw my error.
it also showed up the quality of the machining! I just love horizontally opposed engines, and bulldogs!