how much belt tension do i have to have on the Crankshaft Pulley? how much will the AC compressor need? my goal is to fab a bracket to hold a AC compressor and make it an on board air compressor. in the pic i have the single atl set up all i did was move the belt around the compressor, will that be sufficient tension on the belt to turn with out slipping? in the the stock setup the crankshaft pulley has 70% on the belt in my setup only 50%, and the air pulley only has 20% less then the ac pulley will this work?

 

Clay might be able to help. He sells a belt driven air compressor.

 

I believe these trucks have a self adjusting tensioner (as most vehicles do now). With everything running off one belt, it will take care of itself.

 

^^^ what he said...#3/#8 is your tensioner location.

 

You raise interesting questions that might better be posed to the guys at Gates or another reputable belt maker.

As you are obviously aware, there's more to driving things than meets the eyes, and tension is only one of those parameters. Someone with the engineering expertise in this very discipline would be of big help, but I suspect we don't have anyone on our forum with these specific skills. Of course, who knows? We just might, too!

My concern would be the reduction of circumference percentages, primarily of the crank pulley. If anything, I would suspect the increased load would dictate MORE contact area, not less. The added compressor probably needs the belt wrapped about the same as the current A/C unit does, as well.

You ask tough questions for which I can only speculate, but your fear is mine too, that your belt not only won't do the job, its lifespan will be reduced significantly.

Do you have room for two more "backside" idler pulleys? Of course, that just mechanically complicates things even further, and makes for a VERY long eight-groove belt. That additional length might not even be commercially available, so look into that aspect, too.

Good luck with this ambitious project. You'll have a real winner if it works out for you!

Pop

 

There are so many aftermarket air systems that are available, is an engine mounted system the only option that will work for you? When I added an additional Zena alternator for a welder, I had to add pulleys and a second belt just to run it. If you change the configuration even the slightest bit, the standard belt may not work and you may not be able to locate one. To save yourself a lot of headaches, you might go with a smittybuilt compact air system, an airlift onboard compressor, or a vair compressor system. One of the reasons I purchased my WARN Powerplant HD is so that I would have the additional air compressor. While these systems may be a little pricey, the amount of time, frustration, and additional parts that you may need to make your DIY system work may be far more expensive. Another option is to look in the paper for a used dive cylinder, you can problem find one for 40 or 50 bucks. Go to a local dive shop (if you have one) and purchase on of their old used first stage regulators and have them tune it 90 psi. Pick up some air hose and an attachment and you have an instant compressor that holds (depending upon the size of the cylinder) 80 cf of air at 3000 psi. That is plenty to use for a very long time. When the cylinder gets empty, go back and have the shop fill it up for you for 3 dollars.

 

Are there any DOT regulations about having a cylinder with that kind of pressure mounted on our trucks?

Seems it might catastrophically grenade in a collision if mounted in a vulnerable place.

Pop

 

The DOT regulation is that the cylinder must undergo hydro testing every five years and if the cylinder passes it can be filled for another five years until the next inspection is due. As far as transporting it, it is basically a recreational piece of diving equipment and thousands of people haul them around every day. I used an 80cf cylinder as an example; however, there are many sizes to choose from all the way down to 6cf and you don’t have to jam the cylinder plum full to 3000 psi. You can fill it half way or whatever depending upon how you are going to use it. Some off road shops sell a complete kit that is basically a steel 72 cf dive cylinder for 400-500 bucks. Making up one for yourself from local dive shop parts is much cheaper. As I am a recovery diver I carry HP cylinders in my truck all the time. Obviously the best option would be to set up a dedicated compressor system either through a winch/compressor combo or a dedicated compressor system that could be mounted in the bed or under the vehicle. I know a few guys that carry aluminum 40s with 1000 psi in them just for emergencies on the side of the road like changing a tire with an air tool or adding air to a leaking tire. I would say that the individual cylinder would be my least favorite option but if you had to take a road trip and wanted a little spare air with you they will work well.

 

that is what i was thinking the belt would not grip the pulley with this set up and would slip.

i have been looking at others who have done the same thing and most just add a pulley to the crank and have a second belt run it. i think that is the way i will look into. i have found the belts can be bought and all most any length needed.

i dont like the 12v compressors and most dont have a good life span or warranty, and i have 2 ac compressors than i can use.

 

i have a 3L O2 bottle that was used for people that need o2 in there homes that is DOT good and 3000psi strong so i think i will be ok . and i can get more to have more volume and there ease to mount

 

A 3L bottle will be very small and remember that you need to have a 1st stage regulator that is tuned to around 90psi in order to run tools. O2 regulators will not fit a regular cylinder and I am not sure what the factory PSI is on an O2 regulator. A 1st stage regulator for diving comes standard at around 150psi which would ruin an air tool. Before I get too far into your setup, what are you carrying the extra air for? Many people will carry these for emergencies so it’s not like you need to get them filled every week. The other issue you have to keep in mind is that you don’t want to fill a cylinder to its max capacity and then place it in a hot vehicle because it will expand, not very much but it will expand some. Should not be an issue now for several months but in the summer months you want to avoid this. A 3L bottle is about 0.1 cubic feet of air so that is not going to do much. On a nasal cannula giving some O2 it might be fine for a few but not in filling tires or running a tool.

 

i just need air for tires, and only run 150-200 psi in the tank.

 

Assuming the pulley is the same size wouldn't you just run the same belt and setup as the trucks with the "ambulance package" with dual alternators?

 

If you look at the pic the crank turns clockwise. Problem with this is when the fan is engaged there will be a heck of a bind on the belt drive. That would throw any slack that is pulled toward the tensioner. If you had a compressor right there the belt would possibly have slap in it. Since the crank is the drive pulley as well and the compressor would be behind the tensioner, when it would turn on it could cause lots of slack to happen in the belt. Do you follow? If the comp is hard to turn or was to load up or freeze, the crank would pull against the tensioner and your belt would have a good bit of slack between the crank and compressor. I have the dual alternator set up on my truck and I think your missing an idler pulley to be the same in your pic. Good luck matt. I've always wanted to put a nitrogen bottle under my truck for tires and maybe an air horn. Air tools require a large volume of air to get what you need out of em, not psi. You could have 200 psi and only a 1/4inch line and it ain't gonna perform like 80-90 psi out of a 1/2inch line.

 

So you're basically putting the pump around the area where the 2nd alternator would be? IIRC, they have an extra idler pulley or two in there so the belt gets more grip on the crank and a/c pump. You could probably get those idlers to add in.