Reverse Direction of a Pulley

[MeFB]

Guys, a question for the brains trust...

I need to reverse the direction of a pulley without twisting the belt into a figure 8. To do this I figure I need a very simple gearbox.

Any bright ideas how this has been done in the past?

[EKjimmy]

I know a pulley is a pulley, but if you specify maybe it would help a bit more.

All i could think of is running a serpentine belt like commodores etc so you could route the belt on the other side of the pulley (would require relocating/moving part in question - hence why it could help everyone come up with some ideas for you) but then you need to change every pulley which may or may not be easy/cheap/possible.
Unless you can run something like a square belt (if they even exist?)

Probably not much help lol
Jimmy

[Devilrod]

Keep it simple-ish, run a dual pulley and add an extra belt. If its for the Norman you have I'd suggest running dual belts as a minimum just for that otherwise you may find you will get some slippage on the belts. Most old blower setups I've seen run twin or triple belts, if of course that is why you're asking the question.

[MeFB]

Food for thought there guys, thanks.

Yeah, it's for a supercharger, but it's a Judson, not a Norman. This Judson was designed to rotate CCW as you look at it from the front.

I think the serpentine belt idea might be the go. I can position a small idler / tensioner pulley on either side of the supercharger to bring the belt up from underneath. That's actually very, very clever Jimmy, and simpler / cheaper than a Gilmer drive

[EKjimmy]

No worries. Now that i know what it is for im much more interested

[Craig Allardyce]

Food for thought there guys, thanks.

Yeah, it's for a supercharger, but it's a Judson, not a Norman. This Judson was designed to rotate CCW as you look at it from the front.

I think the serpentine belt idea might be the go. I can position a small idler / tensioner pulley on either side of the supercharger to bring the belt up from underneath. That's actually very, very clever Jimmy, and simpler / cheaper than a Gilmer drive

I wouldn't think this would be possible with a serpentine belt. Considering the belt is only driven on the toothed side, how could you achieve drive in the opposite direction of the crank? Looking at most engines the components that are driven by the crank via the belt are all driven in the same direction. All idlers are spinning in the opposite direction against the non drive flat side of the belt. Not sure how you could achieve opposite rotation using belts unless you could source a belt with drive on both sides but I could be missing something here ???? Another option would be re-engineer the blower drive off the camshaft and step up your pulley ratios by 2:1.

[MeFB]

Food for thought there guys, thanks.

Yeah, it's for a supercharger, but it's a Judson, not a Norman. This Judson was designed to rotate CCW as you look at it from the front.

I think the serpentine belt idea might be the go. I can position a small idler / tensioner pulley on either side of the supercharger to bring the belt up from underneath. That's actually very, very clever Jimmy, and simpler / cheaper than a Gilmer drive

I wouldn't think this would be possible with a serpentine belt. Considering the belt is only driven on the toothed side, how could you achieve drive in the opposite direction of the crank? Looking at most engines the components that are driven by the crank via the belt are all driven in the same direction. All idlers are spinning in the opposite direction against the non drive flat side of the belt. Not sure how you could achieve opposite rotation using belts unless you could source a belt with drive on both sides but I could be missing something here ???? Another option would be re-engineer the blower drive off the camshaft and step up your pulley ratios by 2:1.

Thanks Craig. That's also a very good suggestion about the cam. It might actually be easier to lengthen the cam and modify the timing cover to add an oil seal bearing than go for the belt option. One of the advantages of doing it that way is that I can basically place the pulley exactly as far out from the engine as I need to in order to clear the other components. I guess I'd have to change to steel timing gear at the same time

I quickly did some research after Jimmy mentioned about the serpentine belt, and it seems you can drive off the back of it if you have sufficient 'wrap' around the driven pulley, which is why I'd have to put an idler pulley up on either side of the supercharger pulley

It should look a little like this (the ones in red are idlers, one of which would act as a tensioner):

[MeFB]

The belts for the cam-driven option would be really simple:



Now; what about the cool factor...

Option 1: I used a serpentine belt system because the drive pulley needed to counter-rotate

Option 2: It's a supercharger that's driven off the cam mate

Both very clever, but I think option 2 has that little bit of extra cool (plus if I snap my supercharger belt the car will keep going - which is cool)!

[MeFB]

Hmmmm...except it doesn't really look like that in real life. Water pump kinda gets in the way.

Might have to mount the dupercharger on the driver's side and do the old up-n-over with the pipework. I guess the other advantages of this is that it would keep the dupercharger away from the exhaust heat, I wouldn't have to relocate the genny and battery tray, and I can use the existing Judson outlet instead of fabricating a manifold. Decisions, decisions...

[Trev]

Could it be used running the same way as the engine (back t front for the charger) and just change the carb and outlet over?

[MeFB]

Could it be used running the same way as the engine (back t front for the charger) and just change the carb and outlet over?

I'm not sure Trev, but it's definitely a good thought and the first thing I'll try when I get my hands on it back in Perth.

Might have just saved me a lot of dicking-about Trev

[MeFB]

After a lot of research I found out that you can get 'hex-belts' which are just basically a double sided v-belt (like Craig thought might exist). They are especially for applications where reverse drive on one or more pulleys is needed.

Problem solved