Converting a motor to an air compressor?

[Latte]

I have a need for an air compressor that can run large cfm at 100+ psi in a vehicle. Intend to be using an AC pump with air fittings (see onboard air on a lot of 4wd drive forums). But I had an idea of converting a small 2 or 4 cyl bike engine to run on of the cylinders as an air compressor , and powered by the remaining cyls. Anyone done this before? I was thinking along the lines of running a one way valve off the spark plug hole. And stop the exhaust valves from opening somehow.

Any motors that would lend themselves to this, or would be too hard? I know you can pump up a tire this way on a standard motor but the psi and duty are a lot less.

[mossy1200]

http://thekneeslider.com/ducati-v-on...le-conversion/

[Ocean1]

Used to see the odd VW converted to 2cyl compressor. You'd want something with individual heads ideally, there's a hell of a hassle converting an existing head. An HD might be a good place to start, (make a new head), depending on what you mean by lots of cfm.

Unless you have a lot of time on your hands it's probably cheaper in the long run to buy a compressor and an industrial engine...

[unstuck]

Although they are not widely advertised by many places you can buy compressed air cylinders that you can fill with a workshop compressor or maybe gas station tyre pump. I think a place called Topmaq sells them.

I make my own from gas bottles, takes fuck all to do. But running 100cfm is a little optimistic even for a powered compressor that you buy from repco or supercheap.
I have 2 gas bottles chained in the back of the offroader, which is enough to reseat tires on the bead and air the tires back up.
Also have a hose that screws into the sparkplug/Injector hole in case of emergencies.

[unstuck]

I read that gas bottles can be used too and they look to be made of thicker steel than some of the tanks and budget compressors on the market. I never went through with trying to use one as I would have possibly needed to get a special adaptor made to convert the cylinder connection to an airline connection and I have not seen these on the market.

Most gas and tool shops will have all the fittings you need, I luckily have heaps of fittings left over from my sandblasting days, and get heaps of gas bottles from the dump.

[Kickaha]

I read that gas bottles can be used too and they look to be made of thicker steel than some of the tanks and budget compressors on the market. I never went through with trying to use one as I would have possibly needed to get a special adaptor made to convert the cylinder connection to an airline connection and I have not seen these on the market.

I use a 9kg gas cylinder for topping up tyres at the track, the fittings weren't hard to get

[Yow Ling]

How much is a "large CFM" ? 14" x 14" x 14"

[tri boy]

Call Spraytech in Hamilton. (They are also "Precision Air")
Ask for Chris. (project manager)
Don't ask for me. I'm sleeping out the back somewhere,

100cfm is a fuck load of air to compress at a constnt 100psi. Just saying.

Reread you post. No mention of 100cfm. Soz.
What are your requirements. There are multitude of choices.
Petrol/Diesel, Oiless, Chinky, NZ made/ Pink, Yellow, Elec, etc etc
Check Spraytech web site.

Going by your post, you want to auxiliary air for tyre inflation etc.
Work out your requirements and go from there.
Consider space, hp needs etc
Sometimes a simple petrol unit like a Trailblazer10 works in those situations.
Easy to manhandle and adequate for minor air delivery.
Free Air Delivery at anything over 12-14cfm starts eating horse power, plus a 2 stage pump may be required.
Call chris.

[unstuck]

100cfm is a fuck load of air to compress at a constnt 100psi. Just saying.

Reread you post. No mention of 100cfm. Soz.

After reading that bit of your post, I went back and read the first post. For some reason I read it as 100cfm as well yesterday.

A 9kg gas bottle will handle up to 160psi+ but I only go as high as 120.

[Motu]

Trucks, and other things have engine mounted compressors, just bolt one of those on.

[Latte]

Hey thanks for all the feedback. A lot of good ideas, and obviously not enough information provided in the 1st instance to go on, sorry.

I have 2 ~40 litre air tanks that I'd like to keep between 150-200 psi, but 100+ is ok. It's going in a ute, and needs to be kept under the bed sides. Using a converted AC pump running off the motor I should see ~6-7 CFM @ 100 PSI (2nd hand information). When the tanks are in use this setup wont keep up , but it's close, so I'd like more.

A purpose built engine mounted compressor would be the best bet, thanks Motu. The AC pump conversion is a similar idea to this (I just need to run an inline oiler and a filter to keep it lubricated, and get a header pipe with an air fitting attached. 12V electric compressor options seem to run ~$1000 to get similar volume so my budget is around there, depending on performance, and how noisy.

[unstuck]

Hey thanks for all the feedback. A lot of good ideas, and obviously not enough information provided in the 1st instance to go on, sorry.

I have 2 ~40 litre air tanks that I'd like to keep between 150-200 psi, but 100+ is ok. It's going in a ute, and needs to be kept under the bed sides. Using a converted AC pump running off the motor I should see ~6-7 CFM @ 100 PSI (2nd hand information). When the tanks are in use this setup wont keep up , but it's close, so I'd like more.

A purpose built engine mounted compressor would be the best bet, thanks Motu. The AC pump conversion is a similar idea to this (I just need to run an inline oiler and a filter to keep it lubricated, and get a header pipe with an air fitting attached. 12V electric compressor options seem to run ~$1000 to get similar volume so my budget is around there, depending on performance, and how noisy.

Ac compressor conversions will handle enough to power diff lockers, and perhaps an air gun for cleaning stuff, but would struggle to keep up for tire seating and inflation purposes IMO. Check out some of the latest Bushman compressors for offroad use.