pulleys

[AMY]

Hi guys, a little while back there was a discussion on the weight of the bottom pulleys on the ma10 and ma12. just to let you know that I have weighed both, and the ma10 pulley is exactly half the weight of the ma12 pulley 1.8lbs and 3.6lbs respectively. I wasn't expecting such a large difference, needless to say I now have the ma10 pulley and alternator fitted, along with lower timing cover. Every little helps!

Cheers

Amy

 

[Speedle]

wow thats pretty mad! best be getting me one of thoose! i always said the ma10 was king

 

[ohc_turbo]

every little helps amy, i was the one who spotted this, didnt weigh them though, good job in finding out the weight

 

[Mark]

whats the advantages of having the ma10 pully over the ma12 one?

what effect does it have on the engine?

 

[AMY]

Less inertia, lower rotational weight, similar to fitting a lighter flywheel, or crank etc but on a smaller scale. Don't expect any major differences, especially as the ma10 pulley has a larger circumference, but like i said every little helps.

 

[SammoHung]

so,... do you think that the moment of inertia (result of the compound mass) is still less in for the MA10 pulley, even though is is a larger diameter?

 

[59 bhp is more than enough]

why not calculate it? or give us the diameter and weight and ill do it for you

 

[Andrew]

If the radius of the light pulley is more than 1.41 times the radius of the heavy pulley, then they will behave pretty much the same.

I.e. if the small and heavy MA12 pulley is 8cm across, the MA10 one has to be less than 11.3cm for it to make any difference.

(approximately)

 

[SammoHung]

I knew I'd weed out the scientists among you one way or the other...lol

Interesting conclusons though...nice one!!

I' havent seen the shpaes of each of the pulleys, but i guess if the larger radius one has cut-outs then its effective redius for the purposes of inertia would be close to the inner lump...difficult to explain??

 

[SammoHung]

these two could have the same turning inertia, even if the smaller is heavier (denser)....maybe?

 

[AMY]

The ma12 pulley is a lot wider, it's like two pulleys in one, infact i'm keeping this one just incase i decide to try running a super charger at a later date. I think the larger ma10 pulley is probably around 1.4 times the size of the Ma12 i'll measure them when it stops raining. But at least it weighs less in general rotational or static.
I'm going to look into getting some aluminium pulleys made up based on the ma12 pulley but without the extra width. I have a load of formula 1 piston blanks hanging about which are about the same size, i'll keep you updated.

 

[Andrew]

these two could have the same turning inertia, even if the smaller is heavier (denser)....maybe?

Yeah, it depends on how the weight is distributed. I calculated for a uniform disc, and if the two pulleys have similar profiles, then it kind of holds. It's just an estimate anyway.