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Possible re-invention of the Wheel

TGeorge

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Location
Gardnerville, NV
My 2006 M1078 was acquired with all the bits and pieces for a complete CTIS system. These are currently residing in a box until I'm issued a month of sundays to unscramble them. In the mean time I've discovered airing up or deflating the "Single Super" tires can be a test of one's patience. I needed a shave by the time all 5 were at 85 PSI. ;)

To relieve this phenomena I decided to machine an adapter that would screw onto the valve stem on the rim, depress the schrader core, and allow for easy connection of a Quick Disconnect air line. I was first tempted to use one of the brass elbow fittings used with the CTIS system, but mine are brand new, bright and shiny and I didn't want to sacrifice one, and the elbows have no means to depress the schrader valve anyway.

Probably old news to many here, but the male threads on the valve stem are 3/8 x 32 TPI. That's a bit odd ball, but taps are available for ~$12-20 online. Cutting the interior ORing groove is a little tricky, but I have a Hardinge HLV toolroom lathe so it was not too bad. The threaded machine screw is turned down to about .090 at the tip and for the prototype (and likely one and only example of this to be produced by me) the machine screw allows adjustment of when the schrader is actually depressed relative to how far the body is screwed onto the od of the valve stem. The machine screw leaks a little bit, but no big deal.

It works! I can screw this gizmo on a tire, plug on an air hose and leave it. With a pressure reg the tire fills to the desired pressure un attended. (i.e. while I'm getting that badly needed shave)

Here a few pics, also pictured is the elbow from the CTIS system. I suspect one could achieve the same result by drilling and tapping one of these elbows for a "pin" to actuate the schrader, and then find some sort of adapter for 9/16 x 18 ORB to NPT for the air chuck fitting.

TobinIMG_2986.JPGIMG_2987.JPGIMG_2988.JPG
 

Ronmar

Well-known member
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Location
Port angeles wa
What Ramdough said…

If the CTIS plumbing is intact, you could do the same thing to the feedline (PCU output line to dump valves) behind the passenger dash where the PCU resides… Then you could do 4 at once. The regultor will probably limit flow, but it should be fire and forget. I would not do it without a regulator! On my electric controlled manual system I am the regulator as I must hold a switch to send air to or deflate the tires.

You could even add an adjustable blowoff valve like this…

 

TGeorge

Member
37
60
18
Location
Gardnerville, NV
What Ramdough said…

If the CTIS plumbing is intact, you could do the same thing to the feedline (PCU output line to dump valves) behind the passenger dash where the PCU resides… Then you could do 4 at once. The regultor will probably limit flow, but it should be fire and forget. I would not do it without a regulator! On my electric controlled manual system I am the regulator as I must hold a switch to send air to or deflate the tires.

You could even add an adjustable blowoff valve like this…

Currently all the CTIS plumbing is sitting in a box. All 5 wheels have only a valve stem. I'm aware of the conventional schrader on the CTIS wheel valve. The problem is the common "locking" air chuck for filing car and truck tires won't lock onto the 3/8 x 32 TPI male threads on the valve stem. Maybe I'm the only guy that's deleted all the wheel related CTIS kahooey, but I suspect I'm not.

Additionally many "push to fill" type air chucks for filling truck tires won't even engage over the larger 3/8 32 TPI valve stems.

Tobin
 

TGeorge

Member
37
60
18
Location
Gardnerville, NV
What Ramdough said…

If the CTIS plumbing is intact, you could do the same thing to the feedline (PCU output line to dump valves) behind the passenger dash where the PCU resides… Then you could do 4 at once. The regultor will probably limit flow, but it should be fire and forget. I would not do it without a regulator! On my electric controlled manual system I am the regulator as I must hold a switch to send air to or deflate the tires.

You could even add an adjustable blowoff valve like this…

I'm assuming PCU is Pressure Control Unit. I like your approach. This truck is new to me about 6 weeks ago. The previous owner kept the truck in super condition and was very generous in providing essentially all new wheel valves, fitting and hoses, I just haven't had the time to methodically understand, install and educate myself about all things CTIS. Of course after getting stuck in some soft ground a week ago I'm a bit more motivated. Manually dropping the pressure from 85 PSI to 35 was enough to limit the embarrassment. ;) The time required to bleed each tire and refill using only the valve stem kinda sucked.
 

G744

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Hidden Valley, Az
CTIS was the answer to leaky wheels on late tacticals.

Drive by a guard base and see a lot of trucks listing this way and that, waiting to be started up to set level.

The off-road benefit can be useful, but 95% of where you might drive will get you by with highway-pressure in your tires.

I got sick of messing with those 10x20 O-ring wheels, so I machined a groove to clear a tube stem, and use a flap & tube. No more flats at an inopportune time, chasing down a compressor or firing up the truck to inflate.

Now my big tires stay up for months on end.
 

TGeorge

Member
37
60
18
Location
Gardnerville, NV
CTIS was the answer to leaky wheels on late tacticals.

Drive by a guard base and see a lot of trucks listing this way and that, waiting to be started up to set level.

The off-road benefit can be useful, but 95% of where you might drive will get you by with highway-pressure in your tires.

I got sick of messing with those 10x20 O-ring wheels, so I machined a groove to clear a tube stem, and use a flap & tube. No more flats at an inopportune time, chasing down a compressor or firing up the truck to inflate.

Now my big tires stay up for months on end.
I like to know more about your mod. Are you saying you run inner tubes with a rim liner?
 

G744

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Hidden Valley, Az
That large Schrader stem is popular on lots of ag equipment. I've seen tire chucks for that use at our real tire store.
 

TGeorge

Member
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60
18
Location
Gardnerville, NV
That large Schrader stem is popular on lots of ag equipment. I've seen tire chucks for that use at our real tire store.
I'm quite familiar with the large size schrader and stems. Ag tires, particularly ballasted tractor tires. My LMTV rims use standard schrader cores, the valve stem that projects from the rim is larger than a standard schrader on a suto or truck, but far smaller than the large tractor stems. 3/8" od x 32 TPI I could be missing something, I'll post a pic tomorrow of the valve stems I have. I'd love to have the big bore stems and valves, those move some serious air volume.
 

ramdough

Well-known member
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Location
Austin, Texas
Currently all the CTIS plumbing is sitting in a box. All 5 wheels have only a valve stem. I'm aware of the conventional schrader on the CTIS wheel valve. The problem is the common "locking" air chuck for filing car and truck tires won't lock onto the 3/8 x 32 TPI male threads on the valve stem. Maybe I'm the only guy that's deleted all the wheel related CTIS kahooey, but I suspect I'm not.

Additionally many "push to fill" type air chucks for filling truck tires won't even engage over the larger 3/8 32 TPI valve stems.

Tobin
In that case, sounds like you have a good solution for now.

My system is not functional yet and I have slow leaks in 4/6ths of my tires. Hopefully an easy fix. I have to top off every 2-3 weeks or it takes a long time. I run at 55psi right now, so not as high as you. It still takes forever to fill.


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