R-model front axle identifying. Need help.

[Vladislav]

Recently I bought some chassis stuff off an R-model that was scrapped.

Or maybe it was RD-600, I don't know. All I know is the hood was classic R, not a late one.

There was a complete front axle off it. I would like to use it for my R688ST. Going to take it apart, clean, blast, paint, reassemble and put on my truck some day.

Although I found some differences relating to what I have.

The springs with the hangers and the axle beam look similar. The hubs with drums is another story. My hubs are aluminium and the outer races of the bearings could be spinned in their beds. Not sure it's nice.

The axle I purchased have iron hubs with different style drums. Too probably different knuckles and spindels with bearings. One more thing that took my attention is the different steering arms in the knuckles you put tie-rod ends in. The axle I bought have them fatter.

I suppose I can use the axle all together and it will fit and work fine but some questions bother me.

From seeing steel hubs and wider drums I assume the axle is heavier. Doesn't it meant the springs are heavier also? I don't want to get the ride harder. The truck is a hobby one. Aren't those different tie-rod ends arms applied due to the different track? And the same about the hubs? I'd like to avoid possible track geometry adventures.

There are figures cast and stamped on the axle beams. Does any front axle chat exists or another way to identify who the beast is who?

All thoughts on the matter are very appreciated.

Thanks, Vlad

[Vladislav]

Here is what I have in my truck

 

 

 

 

Edited January 31, 2020 by Vladislav

[Vladislav]

Here's the donor axle

 

 

 

 

Edited January 31, 2020 by Vladislav

[steve p]

Vlad the no is stamped on the spring pad just below the spring

 ie FA 538C ,FA 537 about 10MM IN Height

[Vladislav]

50 minutes ago, steve p said:

Vlad the no is stamped on the spring pad just below the spring

 ie FA 538C ,FA 537 about 10MM IN Height

Steve, do you mean the spring pad as just an area of the axle beam right below the spring?

If the memory serves me right my 1945 WW2 Mack has figures stamped there.

R-model looks as another story. At least I saw no other marks on those two axles I have.

Maybe Aussie R's have their especiallity? My one (I have them two though) was made in Canada.

[steve p]

vlad all mack front axles are stamped that way ,aussie axles come from the states ,even the front axles a friend of mine has imported from the states are stamped that way. yes that pad is correct ,it can be either side as the axle is a uni fit     steve

[Vladislav]

Thank you for the tip, I will twice-check tomorrow.

But it seems to me stamped FA W 537 and 538 in the markings I posed above

[steve p]

vlad the beams are identical in fitment the 538c will have heavier casting for the eye for the kingpin ,the spindle uses the  same bearing as the 537 ,just the casting is heavier around the kingpin area and the control arms are also heavier. here in oz we didn't get 10 stud wheels for r models we had spider wheels so I can't help on that area. just check the drillings for width in the spring packs some were wide and some were narrow drillings       steve

[Vladislav]

Steve, that's very good point you cleared me up with that.

The springs have similar width (my MH has them wider) and as far as I could measure the leaves on the truck they are about the same thickness.

If the king pins are different it's not a trouble as long as I might find correct ones. Or they don't and just the eyes are more massive? They king pins seem tight though and I haven't resolved yet to take them apart for revision or not. Not sure about the wheel bearings in my case, what I have seen they had different marks. But those in the "new" axle are perfect so no need to swap.

One thing that bothers me a bit is the track width. I suppose if both trucks had similar hoods (and axle beams) the tracks should be similar either. Although the hood of the truck with the newer axle had fender flares. Wider front wheels - floaters as American guys call them were there installed? Unfortunately I don't know. Actually I can just measure the distance between the hub flanges on my truck and than relate to the axle. But it's not pretty easy and smooth with the wheels on the ground. 

 

[steve p]

vlad 537, 538 have the same track and use the same kingpin kit .the spring packs are the same ,just check the width of the spring pack drillings on the axles. the wheel bearings would be the same I would think .  steve

 

[Vladislav]

Thanks the great, Steve.

I will check the drillings, just too rainy outside to get under the truck now. I see no reason to worry about that though since I plan to use the beam, the springs and the U-bolts all of one axle, 538. Right at the moment I'm not ready to state for sure the bearings were different between 537 and 538 but my memory keeps it as a right fact. Too maybe the bearings were different since the hubs on my "highway" R seeemed of a light serie, made of alu. But the spindles might be of the same size. I'm going to keep the hubs with drums et.c. of 538 anyway.

Getting deeper into the matters heavier steel (or cast iron?) front hubs will increase unsuspended masses and make a ride rougher in theory. Actually I have no idea of how it will be on a wash board road although I'm pretty sure it's better to have good solid heavy hubs on the truck than light aluminium but of a doubtful condition.

[steve p]

vlad ,we used and still use spider wheels in the N.T. on road train work ,as we have worst road conditions anywhere in the world and we carry the most weight in these conditions ,so I think that says it all

[Vladislav]

Steve, my hats off to your work on dirt roads.

Those spider hubs don't seem to me much lighter than alu Alcoa's on any kind of hubs

Although there's a kind of trick with a truck loaded and empty. A ride smoothness depends on the relation of unsuspended masses of a rig to its suspended mass.

So when you're loaded the second figure goes twice or three times more than an empty vehicle. And as I understand that's the most way a truck is designed to service. But when you're empty with weights of unsuspended parts such as axles with wheels almost the same the relation is different. For example all your axles on a truck weights 2 ton. The rest of the chassis with a cab and engine weights 5 ton. So you have 2:5. But when you're loaded you still have the same 2 ton in axles (unsuspended mass) related to 5 ton chassis and 10 ton cargo. The figure will be 2:15. Here's a big difference. 

A car hasn't much of load capacity so has its mass relation about constant. It gets to be designed along its figure and keeps ride smoothness good in every most road conditions. A truck is a different ball game. Being constructed to carry loads it doesn't run nice on a rough road when empty. Having a hobby one you might be shacked a little bit when your hooby ways put you out of a wide straight highway.

I sure know it's a truck not a boat although taking to account multiple minor factors might work out as a big difference in the end.

The picture is what I have passed with my R a couple years back cruising local roads not far from the middle of nowhere. I haven't shifted higher that 2nd gear with my 9 speed during nearly 40 km. The cost was a 250 km asphalt go over.

 

 

Edited January 31, 2020 by Vladislav