I have considered Gilmer's coz I have to have my power steering belt extremely tight to stop it from slipping, and consider the Gilmer would not need to be as tight, hence less weight on the bearing.
The noise has nothing to do with my application.
bubbles244,
Dec 31, 7:43pm
gilmer belts were originally designed to transfer power on drive axles.
a good example of this is American chopper where they have replaced the chain and sprocket design /driveshaft etc between the engine and gearbox and gearbox and rear axle.
however in an automotive engine application the only time they are really required is when driving a dynamic type supercharger(top fuel drag racing) as apposed to a Lysholm design supercharger (what you get with an eaton in a holden commodore).
The reason for this is one develops pressure with engine speed where as the later develops pressure once reaching high rpm.
due to this the pressure created at low rpm of the first, a lot of friction is required to stop the belt slipping so hence the sprocket type belt or gilmer belt is used.
bill-robinson,
Dec 31, 8:06pm
They are also very good for oil pump drives where one can have varying loads but need a positive drive. Used to drive the pumps on the ford DFV as built by Cosworth. Pontiac used a gilmer belt to drive the overhead cam on their six cylinder engine in the early 60's, then Cosworth developed the BDA for road and race. Using a gilmer belt on a rotary to drive the alternater and water pump is a waste of money in my opinion
brokebloke1,
Dec 31, 8:06pm
I had a silmer problem on a galant we once owned had to have p/s belt really tight to stop it slipping,problem soon turned out to be that the belt was too long previous owner had put the wrong belt on, went down to repco and got a belt 25mm shorter problem fixed. Just check to make sure your not at the full limit of adjustment on the p/steering bracket.
thunderbolt,
Dec 31, 8:45pm
Belky, The synchronous belt does not need to be wide to transmit the power required in this application, and it can transmit the same power as the v-belt with less tension. The decision to over tension and over spec the belt is purely for shits and giggles.
bellky,
Dec 31, 9:33pm
keep on topic and keep your hands off it
edit: (not aimed at you thunderbolt particularly)
cuda.340,
Dec 31, 10:16pm
i'm no expert on rotas but i use M8 belts on my racecar. they're similar cogged belts. an ordinary Vee belt will slip under the quick acceleration of the V8 & usually flip over & quickly fail & no belt is no good. Multigroove belts don't slip as much as a Vee belt BUT you have to have the belt very tightly adjusted which kills bearings. rooted bearings aren't much good either. M8 or Gilmer Drive belts don't slip at all & don't need as much tension & generally things tend to live on the race engine & so does the belt which is a good thing. the average street driven rota with Gilmer drives are from kids who are spoilt little brats who always want this or that regardless if it's any good. perfromance means nothing to them. you only have to stand in the scruitineering bays on a friday night drags to see mods to a car that aren't going to help that car go faster, but the owner thinks they're the bomb.
lookoutas,
Jan 1, 2:35am
Cheers, but got heaps of adjustment. It just breaks loose under max acceleration or when the engine kicks down under a boot-full. Just as cuda alludes to.
The only current remedy is to tighten it more than I'm happy with.
tonyrockyhorror,
Jan 1, 4:01am
Not true. It's not solely a function of tension. Distance from the bearing is a significant factor too.
bubbles244,
Jan 1, 4:50am
also should add to that previous comment for comparison any belt over 35mm in width is wasted as most cars that employ belt driven OHC's use less then that, and then there is twin cam diesels where the injector pump is driven on the same belt as the cams. hence a 50/70 mm gilmer belt on a 1.2/1.3 litre rotary is purely for wank factor as they don't generate any low end torque anyway which is where (in the torque curve of an engine) most belts tend to slip.
thunderbolt,
Jan 1, 5:55am
Ok then, to placate the Pedantic in the thread, overhung load on the bearing can be a factor in bearing wear. But in this case since the pulleys are alloy and the tension required to transmit the required power ( ignoring the over tensioning for noise wank factor) is lower with a synchronous belt, so would extend bearing life in comparison. Small alternator and waterpump bearings were never designed for this of course.
rotormotor7,
Jan 1, 8:35am
A common practice used to be running a twin v belt system on high revving rotaries to eliminate belt slip.
The gilmer belts of course being toothed eliminate this slipping too although it is more for the sound nowdays. I have a set on my 1990 Rx7 and tensioned no so tight as to stuff any bearings, I was competeing at at a hillclimb last year, idling lined up, and heard a dad tell his son "hear that! thats the sound of a supercharger" ;)
saki,
Jan 1, 9:08am
I used the mazda factory racing V belt on all my racing engines about 4 X the price of stock belts but never gave any problems.
quickstitch,
Jan 1, 10:39am
another benefit of the gilmer belt kits (v8 anyway) is that they underdrive the waterpump so you lose less horsepower.
bill-robinson,
Jan 1, 5:43pm
you could underdrive with V belts if you wanted, it is a matter of pulley diameter.
marmatt,
Jan 1, 6:39pm
dont see rotary drag cars with them on!oops hang on just running the fuel pump but they are only about 15-20 mm widewhat makes the noise is the air getting squeezed out of the belt and the pully, look the part but i wouldnt run 1 as got no room
00basil00,
Dec 30, 8:36pm
Why are there so many rotary engines with gilmer belts to drive an alternator and waterpump! Surely it sapping a fair amount of power compared to a v belt and putting a load on the bearings!
bellky,
Dec 30, 8:41pm
saps power; sounds like porn - fair tradeoff
load on bearings depends on how tight it is obviously - tighter = more noise
bill-robinson,
Dec 30, 8:52pm
the load on the bearings will be just as great with v belts maybe more.
r15,
Dec 30, 8:54pm
Its all for the sound
bevharris1938,
Dec 30, 9:02pm
+1 agree , only reason
bellky,
Dec 30, 9:02pm
you have just disagreed (contradicted) me. i really doubt you know what you are talking about. i do however
bellky,
Dec 30, 9:04pm
really einstein! so small fanbelt LOOKS better than fat gilmour - YEAH RIGHT
00basil00,
Dec 30, 9:06pm
Thats just as lame as putting a fake bov on a non turbo car
bevharris1938,
Dec 30, 9:16pm
Who gives a sh+t what it looks like , if it don't make it go faster why put it on !
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