View Full Version : What pulleys??

25-Feb-10, 11:11 PM

Im an final year motorsport tech student, I am designing the drivetrain for an all electric Formula student single seater race car. Im intending to use a 90mm synchro belt, (HTD type) with 14mm Pitch. However, I cant find any alluminium or Nylon ones on the the net, the cast iron are far to heavy, as are the steel. I got reading into your forum's, and it seems like ally is very popular on the crafts. I was wondering if anyone could suggest any brands, websites, etc where i could purchase 14mm pitch, 28 tooth and 48tooth, 90mm wide pulleys made from ally or nylon??

Any suggestions would be really appreciated!



Ewan Black
26-Feb-10, 07:36 AM
We tend to use 50mm, 8mm HTD, which absorbs phenomenal power- the best part of 200Bhp. Are you sure you aren't over specifying for yours?

Most manufacturers can supply as above but from a very limited range of aluminium castings. The smaller pulley will almost certainly have to be steel.

Links to manufacturer's websites can be found on the home page

26-Feb-10, 10:13 AM
[QUOTE=Ewan Black;66759]We tend to use 50mm, 8mm HTD, which absorbs phenomenal power- the best part of 200Bhp. Are you sure you aren't over specifying for yours?

Ewan, my guess is he is specifying close to or within the Gates belts selection guide.

The 8mm HTD only get to 90hp and 6000 rpm input on that guide, that is for general public release though, the actual capability will be higher as you know. Electric race cars can pack more go than petrol ones.

A company in USA called Procharger makes a good selection of CNC 14mm pulleys in alloy and does custom work as well. also Pfeiffer, BDL.

Ewan, I have a question for you regarding pulleys and belts, also open of course to anyone else who wants to :)

I have a efi yamaha engine that is around 145hp @ 7000 rpm, I am not certain but the figure I have for torque is ~124Nm, could be less. This will be a thrust engine only. I would like to turn a fan around 1150~1200mm diameter as slowly as possible to lower noise, ~2050rpm max.

The calcs I have made so far indicate a reduction of ~3.45:1 + is required. I would also like to use 8mm HTD 85mm wide belt system on it. To get a *reasonable amount of tooth engagement area on the lower pulley* and to satisfy some rule I was told that helps wide belts to stay on small pulleys, some ratio of width to diameter that I cannot specify atm, I have selected a 44T for the lower pulley in hard anodised alloy. 3.4 times that is a 151T pulley 381 mm in diameter which I think is out of the question for a top pulley, would be bigger than the fan hub. If the recommendation comes back - stick with 380mm hub or so, then I guess at least the blades will be fairly stiff. I can do 3.4:1 as a double reduction arrangement, 44:72 then 44:84 and the sizes become reasonable and the tooth engagements are still good. One aspect of this is the 44:72 is standard Harley Davidson primary drive which can include a 9 plate kevlar clutch and is mostly alloy and nicely built and available reasonably also. It is a centrifugal ball clutch, and starts to engage around 1400 rpm which is a few hundred rpm above the engines idle. It is fully engaged by ~2000rpm unless it is held by a clutch lever. It can also be locked. Although there is probably no absolute necessity to incorporate a clutch, there may be some slight advantages which may help offset the disadvantages. It is no big deal just to install it locked up either. If closely assembled, the engine driven pulley and clutch basket barely make it past the top of the engine.

The layout that I have for the topmost pulley suits a 12mm wall heavy duty 84T 85mm supercharger pulley redrilled to get the bolt centres closer to the circumference and bolted onto the fan hub via an adapter ring/bearing housing/hub.

the question :- Is anything known about blower pulleys that would cause them to be unsuitable ? Although the driveline has twice as many bits as usual, is this a reasonable path to take to get the fan revs down or should I go a different route ? should I use the carbon GT2 HTD belts or the the powergrip HTD belts. Aramid comes to mind.

I am satisified the the Harley stuff is up to the task and the blower pulley has the same or slightly greater wall thicknesses as the Harley clutch outer.
The craft will be around 4m x 2m, 3 seats and usually operate at around half power but needs to be capable of transmitting full power anyway or it will break for sure.

if fanman would please specify a fan (Hascon type) that would be magnificent.


Ewan Black
26-Feb-10, 11:35 AM
I have to be honest and say that's a really elaborate system for a fairly simple problem. At worst you could probably run 104/30 teeth, which I doubt would have meshing problems. I've run 96/22 with no real problems- although at 50Bhp on a two stroker. You could potentially increase the proportion of the lower pulley in mesh by use of a jockey wheel.

Assuming the engine is out of a bike (i.e. not a pwc/ski) you could use the gears for reduction, this is quite often done, but not an area of expertise for me.

On the other hand, the thought of an OCC primary cover, over a 4" belt, possibly being lit by neons from the ignition leads could set new standards in hover bling:)

26-Feb-10, 12:24 PM
We need that duty of belt due to the shock loading being far greater than a blower, and the motor can produce 800nm at peak torque! The width is due to the length of the belt being short, and therefore requiring a length correction factor.

Is there any specific websites you have used to order? the only place ive found any for sale so far has been on the american ebay?? and cant locate any on procharger.com.

Sorry these are not directly hovercraft related questions, but i do really appreciate your advice.

Kind regards,