Isuzu npr 4wd

[Peter_n_Margaret]

The best units from what I have personal;y seen, are air conditioning compressors, but availability in Australia was one thing, and the eye watering price was another obstacle.

Endless Air Compressor - Prices for Endless Air Compressors, Mounting Kits, Receivers and Accessories.

Powerful & cost effective engine driven air compressor for 4WD, tractor, truck, boat or trade ute. Fan belt driven & minimal power to operate. Deliver worldwide

www.endlessair.com.au

I had a DIY piston style version on an F350 4WD motorhome previously. It was good.
Cheers,
Peter
OKA196 motorhome

 

[SkiFreak]

An engine driven compressor will likely have a better duty cycle than most of the electric alternatives and possibly a higher output too.
Modifying an AC compressor for this purpose is not overly complicated and there are lots of videos out there that show how it can be done. The biggest challenge, for most, is building the bracketing for the engine.
I have a modified Sanden AC compressor on my truck and it works flawlessly. The only wiring it needs is for the magnetic clutch, which is run though a pressure switch on the receiver and an in cab switch, which is used to enable/disable the compressor.

 

[gator70]

Today my air compressor was delivered. It was meant to mount inside the frame rails. When I unboxed it I noticed it was smaller than I assumed.

I had planned on fabricating a narrow tray across the frame rails for this mounting.

And I have about 12 x 12 x 12 extra space now. (inch)

What is a suggestion to mount in that space?

What other smaller on-board item might I need?

 

[SkiFreak]

Buy a bigger air compressor.
Alternatively, use the extra space for a decent sized receiver.

 

[gator70]

Buy a bigger air compressor.
Alternatively, use the extra space for a decent sized receiver.

Can I inflate two 37 inch tires with a Max Working Pressure: 150 PSI / Tank Capacity: 3L (0.8 Gallon)?

 

[Howard70]

Can I inflate two 37 inch tires with a Max Working Pressure: 150 PSI / Tank Capacity: 3L (0.8 Gallon)?

Short answer is yes, but how long will it take? Missing information is output in cfm (cubic feet per minute). With a tiny tank of 3L the maximum pressure really isn't significant as the volume of a 37" tire is many times greater so you'll be filling tires directly from the compressor's output rather than air stored in the tank.

Howard Snell

 

[gator70]

Truck will be ready mid September. Habitat about six weeks latter. (super singles still not delivered yet - so no 37" tires mounted)

 

[gator70]

Currently building rear bumper, using a 85 x 9 inch bus rear bumper as a foundation. A custom swing away spare tire carrier kit is on order. Truck is 81" wide, habitat 2200mm wide.

 

[gator70]

Bought side graphics

 

[SkiFreak]

As Howard has already pointed out, it is the output volume of a compressor that is more important than the maximum pressure it can attain. Another important specification is the duty cycle (how long it can run at full load).
If you are using an undersized compressor to pump up large tyres you can run into all sorts of issues. Speed of inflation is something that you will obviously notice, but if a compressor is running hard it will also get very hot. Hot air will likely produce moisture, unless you have a decent moisture trap in the system. Moisture in your air is not ideal at all.

A larger receiver on an expedition camper can also be very beneficial. Should you dislodge the bead when running at low tyre pressures, you need the ability to "pop" it back into place.
A compressor alone can struggle to do this, but if you have 130 PSI stored in a decent sized receiver, this can provide a "burst" of air, allowing you to easily reseat the bead. There are other ways of reseating a trye, but this is one of the safer methods.

As a side note...
I hope that you realize that you will need some method for modifying the speedo pulse signal, so that when you change tyre size the speedo reads correctly.
I don't know what the laws are where you are, but in Australia there are very stringent rules about how accurate a speedo must be.

Bought side graphics

At this point in time I would think that you have far more important things to worry about than how the truck looks.
Just sayin'...

 

[gator70]

Short answer is yes, but how long will it take? Missing information is output in cfm (cubic feet per minute). With a tiny tank of 3L the maximum pressure really isn't significant as the volume of a 37" tire is many times greater so you'll be filling tires directly from the compressor's output rather than air stored in the tank.

Howard Snell

Thanks, I bought a second air reservoir tank. Both are a good size to fit into voids in between the truck frame rails. My investment is still half of the portable air compressors sold for this purpose.

 

[gator70]

Re Bump stops. I have a dana 60 super duty front axle. With the Isuzu crew cab is new bump stops advised?

 

[gator70]

For Sale

If someone is interested in this rig I'm building. I'm happy to build a second for sale. I've solved all the issues, and the second one would be easier.

In the USA this rig is not available to buy anywhere.

So many parts are GM based, it is very easy to maintain, 300hp, 6 speed auto trans. (engine and transmission from factory)

4wd, professionally installed with warranty from Ridgerock (front and rear air lockers)

Habitat with 55mm composite surfaces, dual pane windows and all turn key living quarters fully equipped

1000 watts solar panels, 600 amp hour lithium battery bank

Dometic RTX 2000 A/C, large skylight hatch, Truma heating and boiler

Articulating sub frame, 5 - 37" 12 ply tires on super single 20" wheels

Cheaper than a Sprinter van.

Nothing is home made. All professionally done.

Seats seven, sleeps four. Leather interior in Cab.

No longer than 24ft in length.

14400 lb capacity.

 

[SkiFreak]

With the Isuzu crew cab is new bump stops advised?

Well, that depends... do you want your fillings to stay in your head when you hit a pothole?
The standard bump stops have little to no softness; if you bottom out you will definitely know it.
Something like a Timbren progressive bump stop is a very worthwhile upgrade, in my opinion.

 

[Howard70]

Thanks, I bought a second air reservoir tank. Both are a good size to fit into voids in between the truck frame rails. My investment is still half of the portable air compressors sold for this purpose.

Hello Gator70:
Are you planning to fill two 37" tires off of compressed air stored in the two reservoir tanks without a compressor? I might have misunderstood your post asking if a three liter tank and 150 psi would fill two tires. I assumed you were looking at a small compressor with a 3 liter tank that produced 150 psi maximum pressure at an unknown CFM rate. If that is not the case ands there will be no compressor adding air to the two tanks as you fill the tires it is unlikely that you'll be able to add a significant amount of air. The volume of a 37 x 12" tire depends upon the wheel diameter, but is most likely greater than 20 gallons assuming a 17" rim and a 12" wide tire. If your two reservoirs had around 1 gallon each (based on your posted question) at 150 lbs psi and you connected those tanks to two tires at 0 psi (after repairing a flat) the total volume of tanks and reservoirs would be around 42 gallons. Boyles Gas Law proposes that pressure and volume are inversely related (we'll ignore temperature to keep this simple). So you've increased the volume around 20 times so you'll decrease the pressure 20 times. 150 / 20 = 7.5 psi. Better than 0. but not much pressure to drive on at any speed above a crawl.

Someone much better at math and physics than me could figure out how much increase in pressure you could get from the reservoirs into the tires at various pressures, but I doubt it will be enough to help you out after airing down your tires any significant amount. Most systems that fill tires from stored gasses go to CO2 or others that can be compressed to liquid states and thus yield effective volumes when released into your tires. Power Tanks are a good example.

Howard Snell