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CAT 3116 A/C pully not really needed? LMTV FMTV

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farmerklaassen

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Recently I've been getting ready to install A/C. Looking at all the options and dying from sticker shock. Upon investigation I cannot understand why anyone would add a pully to the front of the crank pully and not just use the crank pully itself. I've called Gates Rubber and was told by an engineer that the back bend on a 1/2" v-belt is a 4 1/4" diameter idler pully. So what I'm thinking is just using a 2 belt compressor clutch and longer belts, put an idler pully between the crank and A/C to ensure I get enough engagement on the crank pully . Does anyone see anything wrong with this plan? Has everyone else just overlooked this simpler and less expensive way of doing it? I'm looking for feedback, I'm not trying to offend anyone.
 
Reworked LMTV

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Can you sketch out what you are talking about and take a pict of it? Hard to picture.
 
coachgeo

coachgeo

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Reworked LMTV said:
Can you sketch out what you are talking about and take a pict of it? Hard to picture.
Click to expand...
... think I get what he is suggesting.....

question is would the belt surface area and type be enough to spin an air compressor without it wanting to slip easily, eat belts orrr ??
 
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Ronmar

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You would want that idler pulley pushed in farther to keep the belt more wrapped around and engaged with the crank drive pulley. It should have as much belt surface(friction) area engaged as the pulley you are driving...

An issue you will run into is the coolant bypass line is in the same plane as the dual belt pulley, so it would have to be relocated to put anything driven by those pullies on the drivers side of the engine. The plane of the single belt that drives the water pump is behind that bypass pipe so might also be an option for this.

Another option that I have not heard anyone discuss is removing the flywheel damper, taking it to a machine shop and having 6 or 8 serpentine grooves machined right into it. The issue here would be finding an AC compressor clutch assembly with a large enough pulley to keep from over-speeding the compressor at full engine rpm...
 
coachgeo

coachgeo

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Ronmar said:
You would want that idler pulley pushed in farther to keep the belt more wrapped around and engaged with the crank drive pulley. It should have as much belt surface(friction) area engaged as the pulley you are driving.........
Click to expand...
so at least same amount of belt wrap on the crank that is there in OEM setup or better yet even more???
 
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Ronmar

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Would be hard to get more than orig driving tow pulleys in different directions, but as drawn it is significantly less, so a little more would be better IMO...
 
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ramdough

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I like the idea of using those pulleys for additional accessories, but by moving the ac compressor aft to line up with the alternator pulleys, you might have an issue with the aft end of the compressor hitting the service air compressor. Just a concern.


As far as angle wrap around the pulley, the torque that transfers is a function of how far it wraps around the pulley and tension on the belt. You want to match both tension and wrap angle. More wrap doesn’t buy you anything unless the belt is slipping.

Let us know if you can fit your compressor in that space when moved aft.


Sent from my iPad using Tapatalk
 
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cucvmule

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From what I see is the crank at oem has more surface area contact. The proposed belt location has more surface contact on the ac compressor. But is the diagram representative of where the oem compressor would be? Maybe not a good comparison, diagram?

There is belt tension to consider, belt slippage, harmonics of mass in motion whether from centrifugal or linear motion, belt. A lot of engineering has happened to design a system. Believe me I have to WONDER all the time at what mathematical formula that they used when thinking of that design.

As a reference, the belt on the CUCV is long on one side. That long distance has the economics of less parts for repair. However that long distance creates belt harmonics, stretching, bouncing, slippage, friction. Plus when you over tighten the belt more stress on the crank, pulley, bearings on other equipment is created.

I believe that what you are doing has merit. But if you are thinking that you may be able to accomplish the task more economical and get the same task performed then go for it, but make sure about the outcome, for what reason you toil for an effort that has been engineered already. Perhaps their design has merit after all.

Anything that has temperature climate control involved, AC, has a quandary of government reasons, rules that must be adhered to. So then the prices of components also follow with cost.

Great Luck to you and there is always different ways to do the same things.
 
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farmerklaassen

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Thank you to all who replied. My sketch is just that a sketch, the actual would have more belt engagement, the air compressor is defiantly not in the way, yes the coolant lines need to be moved about 3/4" for ether way of doing it. The reply that is of most interest is from "cucvmule", belt harmonics is one thing I had not thought of yet and will definitely take in to consideration.​
 
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Reworked LMTV

Reworked LMTV

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You may want to consider a hydraulic driven A/C pump like Sean's "Abel" on Youtube.
 
m-35tom

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Too much weight hung even further out on the water pump. I am skeptical. OEM cat pulley is only $220 and compressor mounts can be found for around $300, compressor for less than $200. I know it all adds up!!
 
Reworked LMTV

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Ronmar said:
which he no longer runs... He switched to belt drive.
Click to expand...
My understanding was that he did it both ways without issue. He showed both ways for the benefit of viewers. Did he say he had issues with hydraulic??
 
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farmerklaassen

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I have looked at this option before, my truck spends a lot of time off road. The compressor mounted outboard of the alternator in the wheel cavity will not work, it would be destroyed within a week. Thank you for the suggestion though.
 
simp5782

simp5782

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farmerklaassen said:
I have looked at this option before, my truck spends a lot of time off road. The compressor mounted outboard of the alternator in the wheel cavity will not work, it would be destroyed within a week. Thank you for the suggestion though.
Click to expand...
The wheel can not even touch it even at max turn and articulation up. Truck goes offroad alot as is. You could always choose a smaller compressor of your choice
 
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