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Airborne compressor trailer


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While twiddling my thumbs waiting for the weekend my thoughts turned to the missing data plate. The basic trailer chassis were made by one of the trailer manufacturers and then sent to H.E. Nunn of Manchester for completion with the Austin 10 engine and Holman A.T.8 two stage compressor. Looking at the 1949 Chilwell ID list for 2-wheeled Lightweight trailers which includes circular saw, welding and compressor amongst others I see that mine is a Mk2 as opposed to a Mk3 (single piece brake rods whereas the Mk3 have articulated brake rods).

The contract numbers in this publication are shown for the Mk2 as 23/4078, 23/5246 and 23/6069. The Mk3 is 23/7945.

In Rob van Meel's reprint of the Chilwell 'B' vehicle WD number book, the contract 23/4078 is Brockhouse allocated to 'trailer 10cwt 2wh various types', contract 23/5246 is allocated to 'trailer 2wh various' and contract 23/6068 (presumably a misprint) to 'trailer 10cwt 2wh Lightweight (various)'.

I have therefore decided to make up my plate as contract 23/6069 with a WD number between X5827569 and X5827857.

The only compressor plate I have seen is engraved brass (actually just post-war for an Orme Evans trailer, shown in Chilwell as a Mk3).

 

The other puzzle I have relates to my disintegrating pressure relief valve. I have seen photos of three different compressor trailers (plus mine) and all seem to have a different pipe arrangement. Mine is inline between the compressor cylinder head and the engine governor with another pipe going to the air tank - see previous photos in this thread. Another trailer has this valve attached to the plate above the oil dipstick and another has none, Does anybody have any idea about it's function?2015-06-28 11.30.15.jpg

It would be nice to have some feedback as I feel at the moment as though I am in the country of the blind and I am the one eyed man!

AB Compressor 10.jpg

Engine.jpg

AB Compressor 19.jpg

AB Compressor 7.jpg

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The other puzzle I have relates to my disintegrating pressure relief valve. I have seen photos of three different compressor trailers (plus mine) and all seem to have a different pipe arrangement. Mine is inline between the compressor cylinder head and the engine governor with another pipe going to the air tank - see previous photos in this thread. Another trailer has this valve attached to the plate above the oil dipstick and another has none, Does anybody have any idea about it's function?[ATTACH=CONFIG]108301[/ATTACH]

It would be nice to have some feedback as I feel at the moment as though I am in the country of the blind and I am the one eyed man!

 

Hi Tony,

Looking at the photo in your quote here, the valve is attached to the inlet side of the head, see intake filter. I would think that the pipe leading back from the tank is to sense max. pressure in it and opens up the inlet valve so that it stops compressing until pressure in the tank falls to a given pressure and then unloader will reseat. Over the years in service, parts may not have been easy to find and valves of another make or type substituted.

 

regards, Richard

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Hi Tony,

Looking at the photo in your quote here, the valve is attached to the inlet side of the head, see intake filter. I would think that the pipe leading back from the tank is to sense max. pressure in it and opens up the inlet valve so that it stops compressing until pressure in the tank falls to a given pressure and then unloader will reseat. Over the years in service, parts may not have been easy to find and valves of another make or type substituted.

 

regards, Richard

 

Richard, mine may be the odd one out as it protrudes through the roof and whereas the radiator cap hole is flanged this hole is just cut with no edging and so may be a later modification. Even so, why the different attachment points?IMG_9307.jpg

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Richard, mine may be the odd one out as it protrudes through the roof and whereas the radiator cap hole is flanged this hole is just cut with no edging and so may be a later modification. Even so, why the different attachment points?

 

Hi Tony,

On top of the valve is an over-centre lever enabling the operator to put the compressor off load. It may have been a mod to relocate it so it could be accessed easily. I think the over centre lever could be used when starting the engine with pressure in the receiver.

Just found something for you to see, have been searching in the loft, sorry about the text, but you should be able to read it. As I described, the valve opens up the compressor inlet so that it does not compress.

Holman 001.JPG

Holman 002.JPG

Edited by Richard Farrant
afterthought
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A BroomWade "Air-Governor" / unloader would probably be your best bet. Solid brass lump - last for ever & you can BS it LoL , should be plenty around - I think they are one size fits all. I have one on a 1 phase 3hp electric purchased about 1975, unload to start , set switch for "continuous" on governor or "Auto" stop / start off receiver pressure switch.

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A BroomWade "Air-Governor" / unloader would probably be your best bet. Solid brass lump - last for ever & you can BS it LoL , should be plenty around - I think they are one size fits all. I have one on a 1 phase 3hp electric purchased about 1975, unload to start , set switch for "continuous" on governor or "Auto" stop / start off receiver pressure switch.

 

Cannot see how one of those would work on a compressor like the Holman where it releases the inlet valves to stop compressing.

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My BroomWade twin-cylinder has plate valves & it is the signal from the air-governor to the inlet valve(s) that stops compression (just the same) , it has the small lever on top to manually unload , it is adjustable just the sale to set the max. working pressure. Once I had a look at a similar compressor in a quarry but a larger capacity , the governor was identical , the compressor subject of the thread will be within range of both.

 

To me at first blush the BroomWade is a more modern version of same idea.

 

Unfortunately the file for the comp. data sheet, sales literature & parts list + separate instructions for the governor unit are at a garage remote from home.

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Cannot see how one of those would work on a compressor like the Holman where it releases the inlet valves to stop compressing.

 

---------------

 

https://www.google.co.uk/search?q=broomwade+ac+compressor+images&tbm=isch&tbo=u&source=univ&sa=X&ved=0CCAQsARqFQoTCJj49bW2lcgCFYO4FAodKpIADg&biw=1280&bih=900#imgrc=TnBZXukncJyPlM%3A

 

This is the next size up to mine (it has aftercooler fins on pipe from cylinder head to receiver). Note unloader valve plungers, black control box with brass "Air governor" bolted to it.

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A BroomWade "Air-Governor" / unloader would probably be your best bet. Solid brass lump - last for ever & you can BS it LoL , should be plenty around - I think they are one size fits all. I have one on a 1 phase 3hp electric purchased about 1975, unload to start , set switch for "continuous" on governor or "Auto" stop / start off receiver pressure switch.

 

 

From your reply above, you did not indicate your unloader reacted on the compressor valve, it read as if it was a normal electrical cut out type. Subsequent reply from you now indicates it is the same principle.

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From your reply above, you did not indicate your unloader reacted on the compressor valve, it read as if it was a normal electrical cut out type. Subsequent reply from you now indicates it is the same principle.

 

Did

 

QUOTE.

 

unload to start , set switch for "continuous" on governor or "Auto" stop / start off receiver pressure switch.

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Thanks guys for your input - Richards picture is exactly what I have. At the moment we are trying our 'bodge' repair which hopefully I can put inline in due course and, as long as it is not closed, the pressure will not build up but at least I can have the unit running although presumably not have the air pressure controlling the governor. Still a long way to go as I have not even started on the engine.

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Thanks guys for your input - Richards picture is exactly what I have. At the moment we are trying our 'bodge' repair which hopefully I can put inline in due course and, as long as it is not closed, the pressure will not build up but at least I can have the unit running although presumably not have the air pressure controlling the governor. Still a long way to go as I have not even started on the engine.

 

Tony,

If you turn the compressor over by hand and there is no feeling of resistance, I would think there is a problem with the valves, I recollect you were not stripping the compressor, is that right?

 

Richard

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Tony,

If you turn the compressor over by hand and there is no feeling of resistance, I would think there is a problem with the valves, I recollect you were not stripping the compressor, is that right?

 

Richard

 

Richard,

It does turn over by hand but then the air tank is not connected yet as well as the pipes to this b****** valve so there presumably should be no resistance. I have not taken the piston out but had the two head plates off to put some WD 40 down the piston bore to help free it. That, and WD40 over the crank shaft and con rod bearings made it quite free.

I don't think that I am going into the driveway business using pressure tools with this one (sorry David!) as I have seen a film of an exploding air tank and this one was last tested in 1971 according to the stampings on the tank.

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Richard,

It does turn over by hand but then the air tank is not connected yet as well as the pipes to this b****** valve so there presumably should be no resistance. I have not taken the piston out but had the two head plates off to put some WD 40 down the piston bore to help free it. That, and WD40 over the crank shaft and con rod bearings made it quite free.

I don't think that I am going into the driveway business using pressure tools with this one (sorry David!) as I have seen a film of an exploding air tank and this one was last tested in 1971 according to the stampings on the tank.

 

Tony,

Unless the tank has had water (condensation) in it, it may not have suffered, but could be inspected, I guess John will put you straight on that!

There should be resistance as you turn the compressor over even if it is not coupled to the air tank, my guess is the valves are not seating or springs in them rusted away. At least you will be able to run it off load.

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Anthony,

Can you bring the valve and worn threaded connector on Wednesday evening?

 

[ATTACH=CONFIG]108342[/ATTACH]

 

 

I can see the thread issue, which I'd have thought could be Helicoiled, but not sure what you mean by "crazing". Do you think the alloy is corroded through?

The alloy is cracking - the same thing happens to old clockwork train cast wheels and old Dinky toys. Colloquially known as metal disease. My friend Derek (who helps me with the Norton) has taken it in hand and I should be collecting it next week. Helicoils are OK if you can find one to fit the thread and even Rose Autos in Crawley drew a blank - it is a weird thread.

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Tony,

Unless the tank has had water (condensation) in it, it may not have suffered, but could be inspected, I guess John will put you straight on that!

There should be resistance as you turn the compressor over even if it is not coupled to the air tank, my guess is the valves are not seating or springs in them rusted away. At least you will be able to run it off load.

 

I took the head plates off to check the valves - they both seem very clean. The outlet valve has a spring whereas the inlet has a bronze 'claw'. I haven't a clue if something is missing or not.

On another subject, I am renewing the wiring. The original was in pieces and so I am using a NOS rear socket and two NOS tail lights. These lights came with 12v tail/stop bulbs which I am changing to 6v but obviously they are still 2 pin and the input from the towing vehicle is for tail light only.

I have drawn what I think the circuitry should be but no doubt one of the electrical experts can tell me if I am correct or not.2015-09-29 13.09.29.jpg

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I did it the same way as John - although with only one tail light on the offside - so no brakelights - which I assume was the original set-up.. It took me a time to work out that the two pin sockets are not for stop/tail lights but for double contact single filament bulbs. with a wired earth rather than the lights being earthed through the body.

 

Can you get 6v two filament bulbs of sufficiently small size to fit the Lucas or Butler tail-lights anyway? I looked at AES but they don't do the smaller size two filament bulbs in 6v - only 12v

 

I built up a trailerboard attached by wingnuts to the bottom of the trailer's rear crossmember for road use with modern 7 pin plug and socket (only 5 pins used), light units and distribution box. The socket is hidden in the jeep's tool locker as it is an early one with no trailer socket.

Edited by simon king
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I did it the same way as John - although with only one tail light on the offside - so no brakelights - which I assume was the original set-up.. It took me a time to work out that the two pin sockets are not for stop/tail lights but for double contact single filament bulbs. with a wired earth rather than the lights being earthed through the body.

 

Can you get 6v two filament bulbs of sufficiently small size to fit the Lucas or Butler tail-lights anyway? I looked at AES but they don't do the smaller size two filament bulbs in 6v - only 12v

 

I built up a trailerboard attached by wingnuts to the bottom of the trailer's rear crossmember for road use with modern 7 pin plug and socket (only 5 pins used), light units and distribution box. The socket is hidden in the jeep's tool locker as it is an early one with no trailer socket.

 

Simon,

I have just found some single filament, two pin bulbs on e-bay

 

eBay Order Confirmed: 10 x 6V 21W 319 BA15D 6 VOLT MOTORBIKE MOTORCYCLE SCOOTER CLASSIC CAR BULBS

 

I am going to use Johns wiring diagram but instead of the convoy light (not fitted) I will substitute the tandem tow lucas socket

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My friend has come up trumps with repairing the errant pilot valve. He found a fraction of thread left if he took off the fibre washer and so screwed the adaptor in along with some liquid steel, waited 48 hours for it to cure and drilled a hole to insert a steel pin through the alloy casing and adaptor. He then placed an aluminium collar (press fit) to act as a brace.

It is now ready for fitting but I will never have it up to any high pressure. It is also inline with the engine governor but as that is seized at the moment it will be another chapter in the saga!!2015-10-01 18.06.36.jpg

2015-08-30 17.48.51.jpg

2015-10-01 18.06.20.jpg

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