Belts and Tensioners!!!!

topcatcustom · Post by **topcatcustom** » Mon Aug 11, 2008 8:15 pm

Hi again, sorted out the manifold and the nitrous- now thinking about the blower drive belt!

Using an Eaton M112 and I have 2 reasons for thinking I should stick with the standard ribbed belt and pulleys:
1) Price is a priority! (even if a 2" toothed one would look fantastic)
2) If anything goes a bit wrong it will allow the belt to slip a little without blowing something up

Am I talking rubbish or does that sound pretty reasonable?
If I stay with the ribbed belt (I am a fabricator btw) do I need to really tighten up the belt like you do do with a fan belt or does it have to be sprung so it adjusts automatically if it expands at all?

Many thanks

Blown v8 · Post by **Blown v8** » Tue Aug 12, 2008 6:06 pm

dont tighten a ribbed belt as much as your fan belt, you will only burn out your bearings !
a sprung tensioner sounds good, but if no major manufacture has made 1 in all these years. Theres probally a good reason why !
I havent had any trouble with my tensioner, traditional is the easiest way to go ! you want to be unique go for it

topcatcustom · Post by **topcatcustom** » Wed Aug 13, 2008 7:42 am

So is the norm a 'tighten and lock' job- like normal belts?- just wasnt sure if they expanded much when they got warm or anything...
Am I right in thinking that the big toothed belts sap some power too?

kev_the_mole · Post by **kev_the_mole** » Wed Aug 13, 2008 8:53 am

Hi,

no transmission belt should have a sprung tensioner. Belt can jump the pulleys by overcoming the tension of the spring. Tooth belts are 96-97% efficient, ribbed belts a little less and a well adjusted V-belt comes in as low as 92%. If you can machine the pulley blanks we can put teeth on them for you which essentially halves the price and we'll see what we can do on the belt as a V8 Forum special

Cheers,

Ian

topcatcustom · Post by **topcatcustom** » Wed Aug 13, 2008 9:19 am

Thanks, I'l keep it in mind as I havent even mounted it on the engine yet but will definately talk to you when I get round to it, does the idler/tensioner keep it all lined up with toothed belts or does everything have to 110% perfectly lined up?!

Also any ideas on ratio's? Want the engine to last a while and it will be kept pretty standard so thinking around 7/8psi?!?!

kev_the_mole · Post by **kev_the_mole** » Wed Aug 13, 2008 12:03 pm

Usually the driver pulley (crank) should have flanges to guide the belt and the idler should be rigidly mounted as possible. Other variations are possible but would need to see a sketch of your proposals.

topcatcustom · Post by **topcatcustom** » Tue Aug 19, 2008 7:50 am

Any idea what sort of ratio I will need to get the 7/8psi on a M112 atop the 3.9? (so I can start on the pulleys)

kev_the_mole · Post by **kev_the_mole** » Tue Aug 19, 2008 9:19 am

I think this has been comprehensively covered before in these hallowed pages

Do a search on 'supercharger' and you should find some good info.