Info needed: Building a repro LRDG 1940 Chev.

[Bob Phillips]

Hi Bob see my PM
photos are the heavy version of the axle- was just thinking there is a Maple Leaf GM truck at my local yard with a drop front axle- hubs from the CMP straight axle may fit right on....can investigate if it ever warms up
BP

[Bob Carriere]

Would appreciate you looking into the Maple Leaf front axle.... it may fit..... I know for a fact that many CMP were converted to dual rear wheel by simply removing the CMP brake drum/bearing and sliding in place the late GM/Chev dual wheel drum and all.... everything was a bolt on.....

Will see you at the OMVA show.

Thanks for your help.

[Bob Carriere]

....well we palyed with our MDF wooden adapter that allows bolting a regualr 16 in. CMP rim to the 10 bolt Chev front I beam axle........

...it fits quite nicely but gives the wheel a full 5 inch outboard offset and would explain why the LRDG trucks had the front fenders extended/widened by 4 inches.

We also removed the front bearing for inspection ..... and has appropriately nicknamed by Australian/New Zealanders..... "bicycle wheel" bearing of real punny size............

It seems that only the HD 3 ton trucks, COE and C15 had the sturdier roller bearings.

...and the search continues.... still considering all options...

[Tony Smith]

But looking at the color pic in post #9, the wheel is bolted directly to the brake drum without the 4 1/2" spacer. Where would that put you? Will the rim clear the brake drum?

[Hanno Spoelstra]

Bob,

Good to see you experimenting with the wheel/brake drum setup!
That offset will put quite some leverage on the axle stub and put a large load on the bearings. As long as you don’t go lugging around the desert packed to the rafters you’ll probably be fine.

Originally Posted by Tony Smith

But looking at the color pic in post #9, the wheel is bolted directly to the brake drum without the 4 1/2" spacer. Where would that put you? Will the rim clear the brake drum?

Like I said, looking at the WB model, I wonder if they could be civilians rims, possibly widened and mounted inside out? One can clearly see the rivets so this is not a split rim.

http://www.mapleleafup.net/forums/sh...439#post258439

[Bob Carriere]

Hi Tony

On posting #9 that rim when enlarged shows signs of being a rim with an outside ring........ I have no doubt the rim has been modified and possibly mounted backwards....... if it is mounted on 10 bolts then they have to be mounted to a hub/adapter of unknown size as the actual adapter mounts to the brake drum with only five bolts of different diameter to the 7 1/4 diam 10 bolt pattern............ it is unusual and would not be surprised if it was 18 inches....and here is why I think so

If you look at my mock up posting the brake drum is fully cleared of the CMP rim. The inside diameter of the CMP rim is 15 + inches as it is slopped a few degrees as you get closer to the center....and we measured the stock brake drum which measure a hair over 14 iinches....leaving less than a half inch clearance between rim and drum....The other is that the front picture fo Rick Cove's repro shows clearly the front brake drums outside the front rms and his brake drums are ribbed/fins....... which is a variety of brake drums used on those vehicles by GM.

Another factoid...... just got a hold of two new 1940 Chevrolet and Maple Leaf parts book and in the listings.....although only one size hub/adapter of 4 1/4 inch is listed they have four different offset rims sizes ranging from 4 1/8 to 5 1/4 offsets on the rim center parts....all in 20 inches. My spare rim and spare axle has the inside part of the rim even with the brake plate ...this to me implies that it is the smallest offset......... Philippe in Florida has the opposite on his 1939 Chev and his rim clears the brake drum completely. so GM played with the track width by varying the offset of the wheels and the greater offset seems to be on the larger truck axles....series 15 to 18 had the wide offset....... they were not to concerned with the overloading of the bearings. Honestly I am concerned with the old technology and will search to see if I can find roller bearing that fits that particular hub/adapter....... too much unsprung weight to far outboard for my taste.

Hanno.... I agree they are not split rim as far as I can tell.....but have a closer look at the rim/ring edge........looks to me to be a 2 or 3 part rim of that period with the tire pressure locking the rim bead....

The tight fit of the GM brake drum and the split CMP rim may partly explain the reason for using a two part 18 inch rim......18 inches rim where popular in that period and Ford trucks did use them as well.

It would seem possible that a regular 16 in. CMP rim would fit by reversing the location of my adapter plate and mount the rim backwards.... in any event I will play with the mockup to see if I can have the wheel mounted with less overhang..... yet not quite overlap the brake drum...... might be able to gain an inch or so......

Thanks for the interest and questions in this challenging project.

Now looking at finding mid to late 40s production Chev/Maple Leaf 3 ton front axle...... and Ford also had 3 ton I beam front axles...... but only after this snow cover finally melts.......

Bob C

[Bob Carriere]

Clear view of the brake drums fully exposed with implies a healthy offset....

Second shot shoes the civvy hub/adapter which measures 4 1/4 inch and the only size listed in the civvy book.....

A special one does exist for the C15 at about 2 1/2 inch..... but it is using roller bearing along with a CHEV HD I beam axle........ which must match one of the HD front axle such as the Chev COE...... and why not they already used the 4 spoke steering wheel from the COE for CMPs......

[Tony Smith]

Originally Posted by Bob Carriere

Another factoid...... just got a hold of two new 1940 Chevrolet and Maple Leaf parts book and in the listings.....although only one size hub/adapter of 4 1/4 inch is listed they have four different offset rims sizes ranging from 4 1/8 to 5 1/4 offsets on the rim center parts....all in 20 inches.... So GM played with the track width by varying the offset of the wheels and the greater offset seems to be on the larger truck axles....series 15 to 18 had the wide offset....... they were not to concerned with the overloading of the bearings.

Bob C

Ford explained the problem well in their Service Bulletins. Different capacity trucks were fitted with different tire sizes for their weight capacities. This resulted in different tire diameters, but still with the same steering geometry. This would cause tire wear issues on the front tires because the centreline of the kingpin axis should intersect the centreline of the tire contact patch on the road. By using wheels with different offsets with particular tire sizes, this geometry could be corrected and irregular tire wear eliminated.

It should be noted that tires would scrub out and become unserviceable much quicker than wheel bearings would fail from being overloaded or not in line with the tire centre.

This geometry will be a more critical issue in determining your wheel offset than exposing some brake drum.