I’ve managed to get hold of an S26 6x4 tractor unit handbook off ebay. I’m afraid it further muddies the waters!
This particular handbook is an Army Equipment Support Publication dated Dec 1984.
The handbook applies quite specifically to the S26 60 tonne GCW 6x4 tractor, which would put it in Scammell’s mediumweight category.
The engine is the old Rolls Royce Eagle 305 bhp job utilised by the previous Crusader model.
The gearbox, on the other hand is the (then) new RTX 11615. That was the lighter version of the 14615.
The rear end is a SOMA fully floating, double reduction bogie with inter-axle and cross differential locks. Overall ratio 6.39:1.
Basically, this strikes me as an S26 version of the military Crusader that preceded it.
PS I notice that it had an Eberspacher night-heater as standard!
I think that’s exactly what’s shown in the military fighting vehicle transporter that I posted Ro.
I’d deduced that the seeming larger looking hub reduction set up would be the SOMA bogie knowing the Scammell pattern and seeming Rockwell ?.
The S24 and ballast tractor examples show the Scammell axle hub pattern which I was familiar with.
Which would actually confirm the SOMA and medium weight S26 connection.
It’s logical that 65t medium weight would be artic configuration orientated and the SOMA seems like the default choice for 65t spec artic use as shown in the orange unit example?.
Which might also provide a clue regarding the scud’s weight spec if have a clear view of it’s hub pattern ?.
The CM article seems to be close to the mark.
300t heavy = Scammell bogie ballast tractor spec.Obviously heavy artic use needed something different for whatever reason.Maybe more hub reduction needed to compensate for a compromise required in diff and half shaft specs for more axle casing strength ?.
You’re overlooking the fact that Rockwell was an option at mediumweight. Here’s an unhelpful rear view of the Scud, as you can’t see the hubs.
However, I have asked my source for more info. so let’s wait and see…
The Rockwell hub pattern would match the ERF example which you posted earlier ?.
We also seem to have a connection between that of the orange unit and the military examples ?.
The most surprising part seems to be that the Scammell heavy bogie is shown as being higher weight capacity than whatever the 65t artic spec uses.
Unless the shown figures are at cross purposes regarding weight bearing strength, as opposed to tractive effort torque capacity.
The latter would obviously be all about the relative difference between GCW v GTW design capacities.
The seemingly larger looking hub reduction shown on the orange unit and the military artic, possibly pointing to maybe a larger weight bearing capacity, but a lesser torque and tractive effort capacity v the Scammell heavy ballast tractor orientated design spec ?.
That’s why it’s so important to differentiate GCW artic applications, which not only have to provide sufficient tractive effort, but also bear the load of a semi trailer, v GTW ballast tractor applications requiring possibly relatively less ballast weight bearing capacity but more torque tractive effort capacity in the diff and half shaft components.
The orange unit and military artic options shown ( SOMA ? ) possibly using seemingly more hub reduction, to meet their tractive effort requirement, than the Scammell bogie required, but the heavy 300tonner Scammell bogie possibly had/needed relatively less ultimate weight bearing capacity it’s job being to pull loads, not bear the weight of them ?.
To add we’ve got a, not very clear, view of the Scud’s bogie hub pattern in the photo of it coupled to the tilt trailer ?.
They don’t look like the same hub pattern as the orange unit and the military examples ?.
They look like Scammell axle hubs.Again the specs could be at cross purposes in that the Scammell bogie could be ok for both 38t artic configuration or heavy ballast tractor.
But not 65t artic configuration requiring the more specialised ‘SOMA’ ?.
Tummy trouble?
Within a few buttock-clenching paces of the heads. 
Do you have any idea what you’re prattling on about Carryfast?
No. You can’t see the hub pattern on the picture I’ve just posted.
Obviously so long as you can understand the difference between what it takes to pull a couple of hundred tonnes along the road.
As opposed to bearing the pin weight of a semi trailer running at 65t GCW possibly more.
Also bearing in mind the question marks in trying to make sense of what Scammell was actually putting together and why in the clear differences in the S26 specs.
It’s an interesting quest for knowledge not an argument.
Post removed by posting poster.
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You apparently do not understand the concept, but then again you have limited driving experience and no experience at weightsabove 45 tonne.
There are times when a ballast tractor is the only option, but apart from you, and your uneducated fantasy, it is not the first or best choice.
Think about it, without your rediculous bias, it’s not rocked science.
@franglais that is the easiest “seeing is believing” con to get the desired result.
That YT looks a pretty good explanation in clear language.
I don’t think the video I posted can be described as “a con”, if that is what you mean? In the VW video he shows the weight going in the car and correctly explains why.
The vid you posted does show the clear con of the heavy Tesla 4x4 pulling the lighter Ford(?) in 2x4 mode, and it’s claim that it is only power/torque that counts.
The first vid I posted does illustrate your comment that even a Moggie Minor can pull a road-train power wise.
I would bet the 747 was only just moved into position before the vid too. I doubt it had been sat in position overnight, tyres do deflect elastically but there is also a non-elastic component.
And I am not going into issues of hysteresis. ( I leave that for the politics thread!)
One other thing that always strikes me is aerodynamics on F1 and other cars.
The wings etc work very well when the cars are travelling correctly, if the car gets into even a slight sideways movement, “hanging the tail out” then the wings stop working since the air is now going over the wing thw wrong way, the normal reaction (weight on the wheels) drops and grip becomes less so increasing the slide. It all goes very wrong very quickly.
Agreed. The three weight categories clearly have some shared components. We probably need to see each individual S26 on its own merit as many of them could be ‘one-offs’.
Blimey Ro why this needless ridiculous hostility.
What’s your problem with what I’ve said ?.
You clearly posted an example of Rockwell pattern hubs previously related to an ERF example ?.
We’ve equally got a clear match in whatever the military examples and the orange unit are equipped with that I’ve posted previously.
We had some weight ratings and specs in the S26 brochure which you posted.
We’ve got a photo of the Scud coupled to a tilt trailer which is clear enough to show Scammell bogie type hubs.
Is that clear enough for you.
No, I didn’t post it to to contradict your YT, merely to show how the results can be manipulated.
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Sorry mate, I over-reacted. I’ve removed the offending post. It was late and I was tired.
It’s just that I always have to read your posts at least ten times before they make any sense as they are delivered in clauses rather than whole sentences half the time.
You have a knack of bringing out the worst in everyone.
