Any real engineers out there care to explain to the masses the principle of direction of force and magintude that's exibited on the end of the crank at high boost. I think they'd be amazed! It's defend your tuner day here on good ol' F150 On Line. BTW... If my alternator consumed about 60HP to operate I'd want it caged too!

 

...I have witnessed with my own eyes over the years what a supercharger can do to front main bearings, etc.

Saying its like any other accessory is an ignorant statement. I don't care how fast your truck is or how long its lasted with no problems. First off, it takes a lot less power to turn the typical accessories than it does a blower.

Also, consider that the blower pulley is farther out away from the snout of the crank than the other accessories. It doesn't take a degree in physics to understand that this will cause more _leverage_ against the crankshaft. If you don't believe me, go get a 10' long 2x4. Place your foot on one end and your hand about 1' away from your foot on the board. Can you snap the board? Probably not. Now place your hand about 8' out away from the fulcrum. You will be able to bust that thing now! Load/leverage is critical, that's all I'm pointing out.

All this being true...does this mean one setup is better than another or will actually reduce life more than another? I don't know. Taking weight off the front of the crank is very important. This is a plus for the cageless pulleys, no doubt about it.

Another thing is that with the tensioner setup like it is, there is certainly _less_ leverage with this type of blower setup than what many of us might be used to with other blower kits we've worked on/installed. This is a good thing, and b/c of this design a very light cageless pulley might not be any more detrimental to the life of the engine.

I'm just pointing out pros/cons and trying to give some informative data regarding the load a supercharger does indeed put on an engine.

I'm not arguing which one is better. Sounds like there are a number of guys running both with lots of success. Continued best of luck to all of you.

 

First of all, credit to 'awhittle' (apologies if my memory's bad) for the Excel file I have in front of me and the link to Eaton's website.

www.eaton.com/supercharger/M112.html
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Calculation of blower belt load (stock pulleys):

RPM - 5250 (makes the math easier)
blower rpm - approx 13250 (from the Excel sheet)
blower power requirement - 70 hp (extrapolated from Eaton's data)
lower pulley diameter - 7.4 inches (Excel sheet): radius - 3.7 in

70 hp at 5250 equals 70 ft-lbs torque

70 ft-lbs times 12 in/ft = 840 in/lbs

840 in/lbs / 3.7 in = 227 lbs!!!!!

This is the driven side of the belt, the back side (with the tensioner) can't have much load.
----------------------------------------------

Load for JL 4# (corrected)

RPM - 5250
blower rpm - approx 16000 (Excel sheet)
blower power requirement - 34 more than stock (Excel sheet) - 104 {this was wrong the first time I posted}
lower pulley diameter - 8.94: radius 4.47 in

104 hp at 5250 equals 104 ft-lbs = 1248 in-lbs

1248 in-lbs / 4.47 in = 279 lbs.

52 lb increase over stock. This would go up faster with a small upper pulley.
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Cage needed? Who knows? That's a fair amount of load but other vehicles have run unsupported pulleys.

 

Wow...this is some really good information. I have to admit though, I'm still undecided on which route to take. Both sides offer solid arguments for the various setups. This is gonna take more research and investigation than I thought.

 

Tell me about it!

That's why I like this board - everyone gets to share thier knowledge with others which helps individuals make decisions about mods, and understand what you will be getting into before actually doing it.

Anyway, I find this thread particularly interesting since I too am considering a lower pulley.

Thanks guys for all the information!

Sammy

 

It would be interesting to see if a caged vs. non-caged pulley made any HP or TQ differences. Or for that matter, any 1/4 time or mile-per-hour difference. I highly doubt anyone has tested both in a back-to-back situation though. I would think the non-caged pulley would allow more power over a caged pulley, but how much, 1HP, 15HP, none???

 

I have modified 'awhittle's Excel file to calculate total blower load and belt load for different pulley combinations. I will post only with 'awhittle's permission.

 

Why do you think that?

 

Why do you think that?

Per WA 2 FST

Taking weight off the front of the crank is very important. This is a plus for the cageless pulleys, no doubt about it.

I'm guessing less weight equals less rotational force which equals more power. Similar to the theory on a lightened flywheel. It's more of a question from me to someone who may know than a statement.

 

Ebbs, I'm running a cageless pulley and I love it. Its much cheaper and easier to pull on and off in case of warranty work. Btw, did you get my email about the chip? Mike

 

The cage does not rotate. It's fixed.

 

Now THAT'S funny!!!

 

Mike-
No, I didn't get it. I'm out of town right now (on my laptop)....could you re-send it to: PaulSS@prodigy.net

Looks like I'll have to get this chip reburned after all.

BTW....your truck is lookin' Sharp!

 

i went out with a few strippas here in dallas that need dad gum cages....they all move around and squirm or something....and speaking of blowers.. and the thrust...oh jesuz....

 

i agree ,the need to change rear belt without ,the cage there ,makes changing the rear belt much easier,provided you go with a PSP pulley.