gearbox mounted compressor

[Harlé Sylvain]

Hello

here is a picture of my ford Fat compressor, I restore it , it looks in great condition , but I dont understand how it could work without leaking.
The crankshaft is monted on a copper bearing with no seal ,and the aluminium cover has a hole on the botom.

Is something missing?

Cheers
Sylvain

[Lang]

Sylvian

The bottom part of the compressor is just the drive from the gearbox with a crankshaft, connecting rod and piston (just like a car engine)

The air section all happens on top of the piston, like a car. As the piston goes down it draws air in through a one way valve. As the piston goes up again that valve closes and the air is squeezed out a second one way valve into an air tank or air hose.

The round hole in the bottom of the cover is to drain the oil, it needs a plug.

The big opening in the cover is there because, when the piston goes up and down, the volume of the crankcase changes. If you put your hand over it when it is running you will feel air going in when the piston goes up and blowing out when it goes down. When it is running fast at normal speed this will just be a continuous pulsing. This air vent is what makes most of the "choof-choof-choof" compressor noise.

Lang

Here is a drawing.

[Jacques Reed]

Hello Harle,

Just checking my Ford Parts list and there were two types of compressors made for the CMP trucks.

One was Outboard Marine or Saylor-Beall and the other one was Webster- ( your compressor type).

The Outboard Marine type had 3 screws retaining the cover and yours has 4.
Part No. 19947 located at your open cover hole is listed as "Fitting- Lubricator (Webster)"

It may be the type as used on the clutch throwout bearing on the transmission housing but I am only making a guess. Perhaps someone else can confirm what that lubricator was.

Hope this helps.

Cheers

[Jacques Reed]

Hello Harle,

Further to previous post: I believe your concern is leaking at the shaft where it goes into the bottom of the compressor.

If the shaft and/or bronze bushing are not worn, there should be little or no leakage into the compressor base. The viscosity of the transmission oil would also help to prevent leakage. The problem arises if either the shaft or bushing are worn and then transmission oil will certainly pass.

When manufactured, the clearance between the shaft and bushing would most likely be a precision running fit which allows for smooth rotation with minimum play between the bushing and shaft. If sloppiness between the shaft and bushing exists then it would require the bushing to be replaced and reamed to the correct size for the required fit. Most often it is the bushing that wears due to being the softer material. Ford distributors are a good example of this.

If your compressor has seen a lot of use then new bushings would be the way to go or just monitor for any leakage and then decide if the bushings need replacing.

I had a look at a picture of a Webster type transmission mounted compressor that I once had and it too lacked the fitting at the bottom. Wonder if the parts book is accurate?

Cheers,

[Lang]

I just had a look at my box of pumps. I have about 8 of them Chevrolet and Ford. No two are exactly the same and none of them has a name plate. Some cast iron and some alloy.

The plug in the bottom is just a hole for an oil can. Most have a right angle fitting with a little tin flip lid. The one in question has a spring loaded tin lid but coming straight out.

I think so long as there is about an inch of oil in the bottom all will be well as that is the height of the tin lid oiler. If gearbox oil does come along the shaft it can not fill the pump crankcase as it will just leak out the oiler fitting to maintain the correct level.

Quite apart from that there would not be a CMP in ten thousand that used its air pump sufficiently to wear it out when you consider early air brake trucks had similar compressors running continuously for thousands of hours.

Just an observation in my collection are two pumps mirror image to the CMP ones. This gives the option of fitting a pump with the head forward or back to clear chassis rails etc or on the opposite side of the gear box (does not matter which direction they turn) so a winch or hydraulic/mechanical tipper power take off can go on the other side. I had a Dodge WC53 with a winch take-off one side and a compressor identical to a CMP model on the other.

Lang

[Lang]

blitz pump oiler

Here is the oiler on 3 of my pumps. There are two which have no place for an oiler. I looked in the Chevrolet book and they say no maintenance on the pump because it is lubricated from the gear box. In other words they expect oil to go through the bush into the pump crankcase. If it goes higher than the gearbox oil level it will track back into the gearbox by gravity.

Lang

[Mike K]

Were the earlier cab 11/12 vehicles fitted with air pumps ? I ask because my C8 has a tapped hole and plug in the floor where the pump on/off rod would normally be located . I looked into fitting a pump in the C8 but its not easy, because there is a cross member in the way that fouls the pump . Not sure about the larger types 15 cwt and so on.

[Grant Bowker]

I have always understood that Chev pumps mounted on the left of the transmission and Ford on the right, both pointing to the rear. I haven't tried to see if the gears would mesh correctly if pumps are swapped from side to side.
In the Canadian context, and for Chev cab 13, there is only one threaded plug / opening in the floor to reach the pump's actuator shaft. Again, I haven't run a trial to see if all pumps would line up.
I believe all Chevs used very similar transmission mounts. At least the C8A, C15A and C30 up. I'm not as sure about the 2 wheel drive C8 and C15 but would guess they used similar bellhousing and thus mounts so would all suffer similar clearance issues. The 270" engines were mounted differently, whether in C60X or armoured vehicles but locations were similar.

[Lang]

Grant and Mike

Maybe the C8 could have a Ford pump fitted because it would face the opposite direction and possibly clear the obstruction.

The hole pattern and gears appear to be standard SAE dimensions and direction of rotation makes no difference.

Lang

[Mike K]

Originally Posted by Lang

Grant and Mike

Maybe the C8 could have a Ford pump fitted because it would face the opposite direction and possibly clear the obstruction.

The hole pattern and gears appear to be standard SAE dimensions and direction of rotation makes no difference.

Lang

Hmm interesting idea.

BTW the Morris CS8 you drove around collecting sand as a kid on the island, these have a generic SMITHS tyre pump ( fitted on many UK trucks ) on the gearbox side, there is a rod through the wood floor , you pull the ring up to engage the pump . There is a air filter for the pump mounted on the chassis rail , I pulled one apart and it's stuffed full with raw cotton !

[Harlé Sylvain]

Hello
Thank you all for your interesse

There is no problems with my bushings ,they are not worn at all.

I will try to find a oiler, and mount it on a angle on the compressor.

I will cross my fingers and hope that the oil stays in the gearbox.!

Thank you again

Sylvain

[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 !

[David Dunlop]

How do these compare to the postwar, American M-Series 2-1/2 Ton air pumps?

David

[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?