Use crossmember as air tank?

[Tobias]

Does anyone hav experience or input in using the round section crossmember in the rear of a 1997 Discovery chassis as an air tank?

From a quick inspection it looks as if it is just welded to the fram rails, so if the welds are good it should hold air.

Thanks

Tobias

[Soren Frimodt]

Heard of people doing it, just not seen one yet IRL. But in theory you are right, I would hook it up and fill it with air and check for leaks. Its not exactly rocket science to keep in 10 bars of pressure in such a thick piece of steel, so you should just be able to weld any holes up.

We do have a guy here in Denmark who actually has utilized an empty spot inside the front wing on his 90" for an airtank. It is a TIG welded box which is then riveted to the wing with special rivets that can hold up to 34 bars of pressure, and the wing then acts as one side of the tank. Works well and has done so for about 6 years and he only Comps the 90" so pretty good although rather unconventional!

[need4speed]

Neat idea. I like..

[elbekko]

I'd be careful to not pump undried air in there, or it'd start rusting through either the crossmember, or the chassis rails.

[Tobias]

I have a small airtank from an old lorry tucked beside the frame rail on my portaled rrc back in sweden. As i looked underneath the disco the other days for about how much space i had to go shopping in the scrappers here for a tank i saw the crossmemberabd tought" why not?"

I'll drill a small hole and apoly pressure to see what happens before i take any decisions...

Thanks for the input.

Tobias

[Tanuki]

Using closed chassis-elements as vacuum- or air-receivers has a lot of history: Colin Chapman [of Lotus fame] did this on quite a few cars in the 1960s - best example being the Elan.

He was using chassis-rail-entrained vacuum for the pop-up headlights on the Elan. Problem was, when the original welds got a bit leaky, or the chassis-rail suffered rust, the vacuum escaped and rhe headlights popped-up unexpectedly while you were parked.

I'd much rather fit a proper air/vacuum-receiver which you can take off the vehicle for annual pressure-testing. Yes, I've been involved in the inquest after a compressor air-tank exploded because of corrosion... even small amounts of compressed-air can be horrribly shrapnel-spewingly lethal when untested pressure-vessels let go.

[Boydie]

I use it as an air reservoir on my Disco, it seemed o be the logical air reservoir. The twin cylinder ARB compressor is mounted under the drivers seat and a replaceable chemical air dryer is mounted under the floor fixed to the chassis rail. The reserve air supply works well when I'm inflating tyres or the Zodiac. Drilling and tapping the tube was a hassle as I had to do it in from the underside. I went to my local LR wreaker and obtained an axle vent banjo fitting and used it for the air inlet. A "T": fitting on the supply line from the compressor to the "tank" goes to the "snap-on" plug mounted next to the compressor switch. Operating pressure is 125psi.

[Tobias]

The steel was thick enough to tap and hold the thread, then?

I was thinjing of welding on a bung before i read your description.

[Orgasmic Farmer]

I would be tempted to weld a 6mm plate onto it and then drill through that and tap it. Don't think the cross member will be more than 2.5mm at most, but could be wrong?

On my challenge truck I used a 2 gallon tank off a leyland truck. On my 110 I just needed a small reservoir to trigger the rear locker so I welded shut the ends of a 25cm by 100x100mm RHS box and tapped it for a fitting. Works perfectly.

[Boydie]

Yes, about 2.5mm thick would be about right and I agree, if you can weld a small 5-6mm thick plate onto the cylinder first that would be far better. my welding is however very "agricultural" at best and by no means airtight so I just tapped it.