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Alternator pulley belts
MonkeyHunter - 15/9/05 at 12:34 PM

Hi,

On my honda engine the crank pulley drives the Alternator via a 4 groove belt. I want to machine up a new crank pulley to slightly underdrive the Alt, reduce mass, and take a trigger wheel for Megasquirt.

What i want to know is, is there any reason i cant make the pully a 'V pulley' and use a 'V belt' to drive the Alt? I cant see why i cant do this, but then why have honda used a 4 groove belt on the Alt, and a V groove on the same pully for other accesories?

Any thoughts welcome!

Cheers,
Scott.

VinceGledhill - 15/9/05 at 02:45 PM

V belts have been running alternators for ever.

Won't be a problem. Especially considering the low current draw from a Locost.

Bob C - 15/9/05 at 04:35 PM

Use of different belt types - probably to stop the muppets on the production line fitting the wrong one!
Bob

britishtrident - 15/9/05 at 05:00 PM

Polly vee belts are needed if you have a big alternator shove on something like an old Lucas 15 ACR off a Mini and you can get away with a single vee belt -- trouble is with fuel injection I don't thin a 15 ACR would cope with the load a 55 amp alternator might be a better bet.


Strangely just about the first vehicles to use poly vee belts in the UK were old post office vans -- it was part of the special equipment on the GPO spec version of BMC J4 van.

MonkeyHunter - 15/9/05 at 06:18 PM

Thanks guys.

I guess i will have a look and see what cars i can find that use a V belts of arround the right length to drive the Alt, and then make the pulleys accordingly.

Cheers,
Scott.

owelly - 15/9/05 at 10:02 PM

RS components have a good selection of pulleys (incl. 4 grooves IIRC) or try a power/bearing/transmission dealer.

MonkeyHunter - 16/9/05 at 08:50 AM

quote:
Originally posted by owelly
RS components have a good selection of pulleys (incl. 4 grooves IIRC) or try a power/bearing/transmission dealer.


The thing is I want to make it as light as possible, and also add a recess so I can bolt a trigger wheel to it, so I think it would be best to get one made. I will have a look at RS though.

One thing im a little concerned about is that if i make my own pully i will lose the rubber damper that is built into te stock pully, I have heard stories of aftermarket pulleys killing Honda engines, and im not sure if this is the reason, or if its becasue the pulleys are not ballenced properly.

MikeRJ - 16/9/05 at 12:46 PM

You should be concerned! The reason this kills engines, and the reason the pulley is so heavy is because it's a harmonic damper. It asborbs excessive torsional vibration from the crankshaft which would otherwise cause a fatigue failure (i.e. snapped crank) very quickly at it's resonant frequency.

Lightening the pulley will raise the frequency at which it can effectively work, and may raise it above the cranks danger area. Removing the rubber section will stop it working altogether. I would suggest leaving well alone and just adding the toothed wheel to the existing pulley.