CMP windshield throwout arm assemblies

[Lynn Eades]

Charlie, here is my opinion on your center photo.
Top two are CMP. and later U.S Mil. production.
Third down is U.S. manufacture. (eg. 42 Dodge 3/4 ton)
Bottom one is British.

This is just my opinion from what I have experienced. I could well be wrong.

I believe the big cylindrical ones can be converted from pressure to vacuum or vicky verco.
Also my comment about the hill was because when the throttle is closed you get the max . manifold vacuum and when the throttle is down (open) you have very little manifold vacuum, which results in the wipers slowing or stopping.

I have never seen the top one in your first photo, before now.

[Charlie Down]

Hi Lynn,
I'm beginning to think that the shape of the block on the rear of the motor is an optical illusion and that of the 4 motors in your photograph it's the second one down, based on the lever and other details.
This also seems to be quite a common version.
Would it be an option for late 1941?
What do you think?
Do you have any dimensions and photos that I could use to finish the drawing?

[Lynn Eades]

They're not my photos Charlie. I don't know about the dates those units were first used.

[Tony Smith]

The picture of the 4 wiper motors, the top one is the CMP/MCP type. This is a Trico unit known as the S Series. There are a variety of models within this series with different spindle lengths and mounting dimensions, but the operation of the mechanism is the same.

My understanding is that Cab 11/12 CMPs did not have the spacer bracket on the Windshield frame and used a short-spindle S 570 wiper. Cab 13 trucks which had the stand-off bracket mounted to the windshield frame (and therefore possibly the 1533 MCP) used either the S 609 or the S 548 with a longer spindle. Each of these came in a LH and RH version

[Tony Smith]

Note that many US WW2 and post-war vehicles also used the Trico S Series, but there are detail differences with the models used on Canadian vehicles, particularly the mounting dimensions. Jeeps and Dodges used the S 583. The Canadian applications seem to have a simpler design assist lever than the US versions.

While it relates to the physical dimensions of a post-war S Series unit fitted to a CJ2A Jeep, there is a good re-build write up of these units here: https://www.thecj2apage.com/forums/u...uide_rev_1.pdf

[Jacques Reed]

Hi Tony,

Here is the bracket attached to the wiper motor on a Cab 13 Ford. This bracket is then attached to the bracket on the window frame.

Note the arm on the shaft to enable "manual override" when accelerating or under load when the vacuum drops off. (Or any other time when needed)

I have two different length shafts of the same type bracket. This is the shorter one and I am using the longer version on my cab 13.

Thought this might be of some interest.

Cheers,

[Charlie Down]

Lynn, Tony and Jacques,
Thank you for all your information.
I have a clearer understanding now of the motor and various model setups.
All I need now are some dimensions to finish the drawing.
I've attached a rough sketch to show the dimensions in question, from which I should be able to scale the rest.
Any help would be greatly appreciated and drawing posted when complete.
I presume (which is always dangerous!) that the main dimensions will be similar throughout the different models, with only details like mountings and spindles varying depending on model.

[Grant Bowker]

Originally Posted by Tony Smith

My understanding is that Cab 11/12 CMPs did not have the spacer bracket on the Windshield frame and used a short-spindle S 570 wiper. Cab 13 trucks which had the stand-off bracket mounted to the windshield frame (and therefore possibly the 1533 MCP) used either the S 609 or the S 548 with a longer spindle. Each of these came in a LH and RH version

I agree that there wasn't a spacer added to the 11/12 windshield frames (at least in the context of Canadian Chevrolets) but the frame was made of tube/pipe plus the panel that held the glass, so the total thickness was similar to the cab 13 frame with spacer. To my eyes, the proportion of the s-609 motor looks closer to what I'm used to. Attached photo shows what I think of as a typical motor both with and without the support tube for the wiper shaft.

[Grant Bowker]

I recently had the chance to sit 3 arm types (Canadian) side by side for comparison.

[Grant Bowker]

Measured on the right hand motor in the post #38, I get the following dimensions:
A - centre to centre of mounting screws 4-11/16"
B - overall length 5-5/16" for the wiper casting, 5-3/16" for the bar holding the support tube
C - width of support bar 21/32" (mounting tab on motor casting 39/64")
D - thickness over tin shield and mounting bar 2-5/32"

E - D minus the support bar ~very close to 2" tin cover to mounting feet, but the dimension varies depending whether you measure to motor mounting feet, motor lid or motor body

F - width of tin cover 2-5/32"

G - height of tin cover 2-1/4" (dim. from top of tin cover to bottom of wiper bowlcasting 2-1/2")


Additional dimensions:
length of support tube for shaft (measured from face of support strap) 1-27/32"

length of wiper shaft (measured from face of support strap) 2-1/4"


The spacer strap on the inside of cab 13 windshield (measured on a Canadian Chevrolet) is made of 3/4x1/8" strip. Air gap between windshield frame and spacer strap 5/8". tip to tip measurement as mounted on frame approx 7-5/8" (imprecise due to welding on ends). length of surface to support wiper motor 6-1/16". Centre hole diameter 3/8" + clearance. Distance between outer mounting holes 4-11/16". Outer mounting hole diameters 3/16".

[Charlie Down]

Grant,

That's brilliant. Thank you.
I was about to post a further request for dimensions, but clearly there's more than enough to get my drawing finished now.
I'll spark up the CAD programme and hopefully get it finished over the weekend.

[m606paz]

Arms one Chevrolet with serial number?