Fan belt roller guide demonstration

[isucorvair]

For reference, take a look at the fan belt dance (especially during shifts) in this video found on youtube.
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Its my video. Thats my 66 autocross car, 95hp, Powerglide, in low gear for a short autocross (I never autocross in Drive). It was running old stock transmission mounts, and a Clarks HD Engine mount.

Eric P.
DeWitt, IA

[davemotohead]

Kevin, Have you thought about using replaceable rubbing blocks instead of rollers? Might solve the bearing problem?

[Nashfan]

Kevin, Have you thought about using replaceable rubbing blocks instead of rollers? Might solve the bearing problem?

Sort of, for a minute or 2, then I realized that they would wear out way quick! The more they wear the worse the belt control. The other thing, even if the bearings do seize on this, they become "replaceable rubbing blocks", except that being the rollers are made from stainless steel, can handle that for a long time, and can easily be trued up. My set has gone 3000 miles and theres nothing wrong with them, except I had to take the engine out and replace the pistons, cylinders and some other stuff so cant do any testing for awhile. The rollers are currently set-up to only allow .012" of belt movement, and one of the tester's has gone a few hundred miles on it, with a super tight belt, and really rev's the hell out of it! He told me the other day he was on the freeway for 15-20 minutes and revs between 4000 and 6500 and simply isnt seeing any roller problems that he had before. He's trying to kill that thing or pop a belt!! Showing the benefits of oiling the bearings properly and having a good inner bearing race support and bearings that are meant for that kind of speed and load.

[Nashfan]

A little update on the testing- the first person to receive the updated rollers told me he's coming up 1000 miles and carefully inspected the rollers and theres zero indication of bearing overheating or overloading like before... both rollers are just as free and smooth as the day he installed them. Its interesting though, the left roller is uniformly shiny where the belt contacts it, which would be expected if the belt is in continuous contact, which it is. The really interesting observation is that the right roller has some shiny spots on it also! It goes to show that even with a seriously tight belt there's a LOT of potential chaos being stopped before something bad happens, because the only way for the belt to contact the right roller is if the belt gets momentarily loose and would not seem possible if the belt were tight enough.

[kmart356]

This is from a different tester... the left roller is spinning nicely while in contact with belt and you can see the right roller is not spinning but does have some belt smudges on it.

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[Nashfan]

This past weekend, probably one of the toughest tests for the roller guide happened. The engine is a 3.1 liter triple throat weber running a Nashfan, aluminum airflow pulley and aluminum idler pulley, and a fairly nasty cam. Its an autocross car and in the past it has tossed belts or rolled them every single time on the course. Literally everything has been tried to stop the belt tossing.
Until now... installed the roller guide and no belt tossing or rolling. His shift points were at 6400 rpm, and had 4 separate runs on the same day.

[Wittsend]

It is good to see that the roller guide is progressing with positive results. Curious, at the stated 6,400 RPM has anyone calculated how many RPM the roller is turning at? It is a small fraction of the crank pulley and must be spinning at some, 5 maybe 6 digit RPM!

[Nashfan]

It is good to see that the roller guide is progressing with positive results. Curious, at the stated 6,400 RPM has anyone calculated how many RPM the roller is turning at? It is a small fraction of the crank pulley and must be spinning at some, 5 maybe 6 digit RPM!

Just kind of roughing it out, at 6400 rpm, the rollers should be in the neighborhood of 55000 rpm. They are supposed to be able to handle 7000 engine rpm, as this is roughly 60000 rpm. Theres some additional margin with these bearings in that they can handle more than that if oiled which they are. With roller bearings, the speed rating is super important, but also its the loads at that speed that are even more important. Fortunately, the rollers only have to carry a tiny fraction of the load that the idler bearing does relative to the actual total loads they are able to support!
This dynamic has to do both with the comparatively large forces on the idler bearings just from belt tension, AND the miniscule force required for the rollers to push back on the belt to keep it running straight. The less off line the belt is coming in the less force, the faster the rollers correct the offline tendency entering the less force, both of these situations are handled in a near instant, stopping a possible large deflection while it is still tiny. The other neat thing about this dynamic is how the rollers can affect the tension in a positive way... if the belt trys to enter too off line, it creates some drag, and AUTOMATICALLY causes extra tension on the exit side, which is good, as it will tighten up the part that needs tightening and the extra tension also helps pull the belt through more straight. Lots to be had by killing the monster before its born!!

[Nashfan]

Today a different autocrosser tried out his roller guide and now officially owns the rpm record at 6800 rpm. This was done with a full size mag fan, steel pulleys and an extra tight fan belt. I expect he will be breaking his own rpm record fairly soon when he has a need to change his rev limit to 7k... his engine is built to handle this. Fan belt stayed on all day long.

[martyscarr]

Nice, are these going to be available soon Kevin?

[Nashfan]

Nice, are these going to be available soon Kevin?

Yes they are! I have one for sale immediately, and wont have more inventory for a couple of months. They are 275.00 + shipping

[toms73novass]

Well, I finally got mine out of storage. Install in process. Quick shifts here we come!

[toms73novass]

Really banged the gears and the belt is rock solid!! Hit rev limiter 6k a few times. I would have no doubt had issues before.

[Nashfan]

Really banged the gears and the belt is rock solid!! Hit rev limiter 6k a few times. I would have no doubt had issues before.

Right on Tom!! Have you tried speed shifting yet?? supposedly this is when the sh!t REALLY hits the fan

[toms73novass]

Really banged the gears and the belt is rock solid!! Hit rev limiter 6k a few times. I would have no doubt had issues before.

Right on Tom!! Have you tried speed shifting yet?? supposedly this is when the sh!t REALLY hits the fan

Yup as quick as I could.

[American Mel]

.Cool stuff.