gearbox mounted compressor

[Phil Waterman]

Hi Everyone

Can someone confirm my recollection that these transmission driven air pumps are not intended to operate full time? That the gearing is such that much above idle speed they are being badly overspeeded.

My memory is based on something in a manual, drivers handbook, or service bulletin which I can not lay my hands on at the moment.

Cheers Phil

Brought back one of these from the War and Peace Show years ago in my carry on luggage through Heathrow. Trouble going through security at that end and customs at this end. They do look strange on the luggage xray.

[Jacques Reed]

Good Day All,

The attached should answer all questions on where the oil goes in lubricating a transmission driven tyre pump.

Taken from Ford "Special Pattern Vehicles" book. Note passage "A" and wick and non-wick versions and elbow oiler as mentioned by Lang.

The lubrication must be very slow as my pump, missing the oiler, sat for years on a working vehicle in my driveway. Never saw a drop of oil on the driveway under it.

Cheers,

[Lang]

Just at a rough guess I would think the pumps I have, which are mirror images, are for either Ford or Chevrolet application. Both manufacturers probably used the same pump suppliers.

CMP vehicles would not have had exclusive pumps and they would have been a carry-over going back 20 or more years for all sorts of applications. I bet an air pump was offered as an after market accessory for most trucks at the time.

I would think Phil is correct in assuming these particular pumps were not for continuous operation and designed for idle speed tyre filling only. Trucks operating air pumps continuously for air brake systems would certainly have much different gearing.

I have no idea, but I think there may be a physics equation giving the optimum speed of a particular pump design and that is why modern high capacity pumps are screw systems which maintain the flow in a continuous direction rather than pistons.

Lang

[Jacques Reed]

Originally Posted by Phil Waterman

Hi Everyone

Can someone confirm my recollection that these transmission driven air pumps are not intended to operate full time? That the gearing is such that much above idle speed they are being badly overspeeded.

My memory is based on something in a manual, drivers handbook, or service bulletin which I can not lay my hands on at the moment.

Cheers Phil

Hi Phil et al,

Again, from the Ford "Special Pattern Vehicles" Manual they say bring engine up to 900 RPM or 16 MPH equivalent engine speed as per attached.

I agree, it sounds a bit fast but perhaps a later service bulletin countermanded that instruction. I never used mine, but if I did, I think nothing more than a fast idle would be the way to go.

Cheers,

[Phil Waterman]

Hi Jacques

900 RPM sound reasonable, my trucks idle at about 400 RPM and the 216 is maxed out completely around 3200RPM. So the 900RPM should be a reasonable speed.

I was just concerned that somebody down the line would read this thread and not realize that you have to disengage the thing to drive the truck. Can just see somebody whipping down the road at 40 MPH and wondering what the hot oil smell was coming from. Along with the all the strange sounds coming from under the floor.

Cheers Phil

[Richard Coutts-Smith]

Humber One ton used the same set up (It was a design used for quite sometime) with the Drivers Handbook warning not to exceed 1000 RPM. Unfortunately it can be all too easy to drive off with them engaged, and they go all wonky...
Rich.

[Mike K]

This is the generic SMITHS version , from my Morris CS8 but also fitted to many UK vehicles.

I guess the drive gear would be a different setup for each brand of vehicle, eg the gear diameter and the no. of teeth . Made in cast iron, not the wimpy soft alloy that the Chev pumps are made from.

[Lang]

Mike

I suspect the American pumps were pretty standardised as I have fitted CMP pumps to Dodges OK (I know the Ford and Dodge gearbox are very similar.)

They all appear to have an SAE standard bolt pattern on the boxes for power take-offs. I have seen power take-offs on the same gearbox attachment for winches, bag lifters, tipper drives and hydraulic pumps. As you say there could well have been gear variations.

I think I might prefer the modern precision made Chevrolet alloy pump over the 19th century sand cast Morris iron effort. The CMP cast iron pumps are still much prettier than the English version. Suppose it does not matter as I mentioned before, the hours of use of any off them would last a hundred years - if you did not drive off with them engaged!

Lang

[Mike K]

A page from the WW2 Austin K5 drivers handbook. This one appears to be a RH version, the Morris has the pump on the LH side of the gearbox. The filter unit is identical to the Morris unit.

Notice the deluxe air pressure gauge which is absent from the CMP pumps !

[Tony Smith]

Originally Posted by Mike Kelly

This is the generic SMITHS version , from my Morris CS8 but also fitted to many UK vehicles.

I guess the drive gear would be a different setup for each brand of vehicle, eg the gear diameter and the no. of teeth.

There is a Smith's Pump currently on E-bay:
https://www.ebay.co.uk/itm/SMITHS-MI...NrC:rk:45:pf:0

The body appears similar (but mirror reversed) to the Morris CS8 pump, but the drive gear is quite different. In fact, the E-Bay pump looks very similar to the arrangement on Ford CMPs. I wonder if this was actually design for a Ford application, or some other British vehicle such as the Austin K5?

The Smiths Pump body looks quite smaller than the CMP (Ford or Chev) pump, so I would expect a smaller output of air. Are there any specs regarding the volume/pressure output of these pumps?

[Lynn Eades]

Lang, are you aware that the 4 speed Dodge and the 4 speed Ford of that era, use the same cluster gear?