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stal108

S26 scammell & DAF Drops

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Wheels and tyres .

Well ill tell you a story. I was allways dissapointed with the top speed of my s26 self load dump truck (sldt).51MPH FROM A 350 ENGINE AT 2200RPM.

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So i bought a set of 1600x20 off a foden wreaker. They are so much bigger at 2200rpm it does 67mph.. so now at 55 it runs very sensible 1800rpm with lots of power and torque. Ready for the next hill. This has also make a massive difference in mpg.

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Hi Stal.

 

The scammell Drops mmlc's were origanly built with 1600x20 but were changed because of two

roll overs that happened on trials. The MOD asked for the smaller tyres that are fitted, but left the axle ratio's

as they where hence the speed difference.

 

I think this is the same that go's for your S26 sldt. I know that Dave crouch's EX-Army Demo 6x6 S26 recovery is

on 1600 x20 which if i remember correctly was scammells standard tyre for the MOD's S26 model.

 

 

Regards

 

Clive

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The mmlc drops wont take 1600x20 they touch on the swinging arm hub on the back. There is a chap last week tried to fit them( MY IDEA OPS) .I am very supprised myself but i am sure drops were allways 18x22.5. Even the pics in trials were 18x22,5.. So not sure where you got the info.DC has the s26 demo wreaker and yes 1600x20 thats where i got the idea for the sldt. No idea that they had changed the rear bogie setup on a drops and no idea why,

I have a foden drops and i thought about a daf with 20.5x25 and put the civi wheel arch on as the t45cab to cover the larger offset but i do not think there is room between the front tyres but love to try.

pics tony sent me,,drops

i MIGHT BE SELLING THE FODEN ..maybe px a daf

cars_014[1].jpg

cars_013[1].jpg

les%20recovery_48.jpg

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In this pic you can see the swinging arm.. no idea why on a drops it is in the way there is miles of room on a sldt rear bogie

22092011495.jpg

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In this pic you can see the swinging arm.. no idea why on a drops it is in the way there is miles of room on a sldt rear bogie

 

The difference in the rear suspension between the rear of the SLDT and the Drops is.

 

SLDT is bolted to the outside of the chassis rail with bolts going through the two arms into the bogie crossmember.

 

Drops rear suspension unit is different. it is bolted to the bracket which mounts on the outside of the chassis for the multilift body mounting bracket. it dosn't have the mounting arms with bolts going through the chassis. but has bolts that go downwards through the bracket and into the bogie unit.

This brings the bogie unit out some 40mm or so per side.

 

Dave Crouch's rear bogie unit is the heavy duty Dana system or Kirkstal system as it was known back then,

This unit was also used on the rear engine scammell nubian airport crashtender.

 

The issue i think you had trying to fit the wheels and tyres that you had, was that the centre nave position on the

original drops rims compensated for the difference with the 40mm in the suspension unit position.

 

Hope this makes more sense and answers your question.

 

regards

 

Clive

Edited by protruck

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Hi Stal.

 

The scammell Drops mmlc's were origanly built with 1600x20 but were changed because of two

roll overs that happened on trials. The MOD asked for the smaller tyres that are fitted, but left the axle ratio's

as they where hence the speed difference.

 

I think this is the same that go's for your S26 sldt. I know that Dave crouch's EX-Army Demo 6x6 S26 recovery is

on 1600 x20 which if i remember correctly was scammells standard tyre for the MOD's S26 model.

 

 

Regards

 

Clive

 

Mmmm thats not quite as I remember it (I led the DROPS User Trials Team in the 1980s)

 

The issue with the MMLC was getting the thing to meet the criteria for medium mobility whilst staying within the construction and use dimensions and acheiving the necessary tilt figure (and therefore stability round bends and on side slopes cross country) This was particularly problematic with the DROPS as the load handling system raised the centre of mass of the load rather a lot.

 

MOD wanted the ground clearance, Scammel resisted, but eventually the MOD boffins prevailed and the "big wheel" MMLC was rolled out at Chertsey in front of a group of senior folks, whereupon during the demo it decided to have a lie down on its side.

 

So back to the original wheels it went.

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I could see there might be a issew with the extra hight on 1600 as i would indeed lift the centre of gravity.. aslo load deck hight. But not a squaddi driving rolling it over is less likely...lol

My foden has a deck hight of 6ft6 at the front and 6ft.4 on the rear so a max load of 10ft high.. i put a stolly with a crane on and had to let all the tyres down with the stolly on backwards to get under 16ft6in(min motorway bridge hight and notification) the 432 fits fine took one to beltring this year no probs with anything.

All i was thinking was speed and econemy so going larger tyres was an easy option .But it seems no so easy .Is there any other tyre that will fit the 22.5 rims that will be taller?

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If the only issue is position of wheel centre in relation to rim (i.e. offset), you may find it relatively cheaper to get rims altered or new ones made to your specific requirements - try Tony Rosenthal at

 

www.kirkbytyres.co.uk

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What i think is the problem is if you look at the pic of the drops front bogie the red wheel has a different rim to the front one ,, the offset is different, i think this may solve it. I hope. Tony is off to DC place today so hopefully we will have an answer. But if it works it will make a drops even better.

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Hi,

 

I'm new to the forum, I've got a Daf Drops, which I use at work for engineering support and being generally useful. I've had it desertised and it was also used in the Dakar in 2013, very useful as a support truck but struggled with the distances and times due to top speed.

 

It was used alongside a Drops equipped Man Kat a1 which has a top speed of over 60. Neither vehicle had much more than 6-8 tonnes in a converted ISO container on the back, so not overloaded, but empty or full the Daf only does 47mph and is thirsty (than the Man). We had a few Drops REME experts on the team (had been on Drops) all stated that the engine has a mechanical geared governor system (I think) so it can't be easily changed. It appears that larger tyres are the only option unless someone has any ideas on gearing changes etc?

 

I hope to use it again on another rally raid or similar but with a top speed of 47 it's not practical. So that people understand, even on a road support stage the support crews have to make specific times. You also have to be in before the racers so if you cannot make the speed limits I.e. 55mph or similar, which stage transfer times are calculated by, you'll find yourself arriving after the main team which is obviously pointless. I don't see the side angle C of G change being an issue with bigger tyres as the load is low, secured and probably no more than 6 tonnes. Any ideas or findings would be very helpful. I'm thinking of changing for a Man Kat but this would be unnecessary if the top speed can be sorted and I may get another. From the last thread I couldn't make out if there was a final agreed best practice or indeed if anyone had done this on a Drops in practice.

 

Very best Charles

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Charles, the easiest way would be to change the final drive ratios and I would suggest a call to Smiths at Albrighton to see what alternatives are available. http://www.hlsmith.co.uk/

 

On the Scammell S26 6x4 the answer was to use the diffs out of the RAF tanker which gave a change from 6.39:1 to 4.79 IIRC and a top speed of 69mph against 52mph.

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RadioMike,

 

i called smiths and they've asked for some details on the axles and/or diffs. The truck is stored in the South West at the moment so I can't readily check. I wondered if you or anyone else new what the spec was on the daf drops, it's a 91 model.

 

ive also contacted Dave Crouch, who provided me with an engine previously, he's offered me a set of larger wheels off an AEC mark 3 wrecker, which he thinks will fit and will check but the price is pretty high, although the diffs will be costly too. Which do you think, regardless of price which is the better option? I assume diff exchange due to CofG, clearance etc but as it's all 3 differentials smiths were sceptical on the price to do it but need to check specs first.

 

regards

 

 

charles

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RadioMike,

 

i called smiths and they've asked for some details on the axles and/or diffs. The truck is stored in the South West at the moment so I can't readily check. I wondered if you or anyone else new what the spec was on the daf drops, it's a 91 model.

 

ive also contacted Dave Crouch, who provided me with an engine previously, he's offered me a set of larger wheels off an AEC mark 3 wrecker, which he thinks will fit and will check but the price is pretty high, although the diffs will be costly too. Which do you think, regardless of price which is the better option? I assume diff exchange due to CofG, clearance etc but as it's all 3 differentials smiths were sceptical on the price to do it but need to check specs first.

 

regards

 

 

charles

 

Hi Charles.

 

Dana SD66 / kirkstall axles. With 7.46:1 diff ratio's.

 

regards.

Clive

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Hi Charles.

 

Dana SD66 / kirkstall axles. With 7.46:1 diff ratio's.

 

regards.

Clive

 

With respect, you didn't mean that did you Clive:-)

 

To clarify, the overall axle ratio including the reduction hubs is 7.46:1, the crown wheel/pinion (diff) ratio will most likely be in the range from 2:1-3:1.

Edited by radiomike7

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14.00 x 20 wheels and tyres will fit, see Hamptons website, they have a couple already done. Not sure how much quicker but certainly a bigger rolling radius.

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Charles, the easiest way would be to change the final drive ratios and I would suggest a call to Smiths at Albrighton to see what alternatives are available. http://www.hlsmith.co.uk/

 

On the Scammell S26 6x4 the answer was to use the diffs out of the RAF tanker which gave a change from 6.39:1 to 4.79 IIRC and a top speed of 69mph against 52mph.

 

Would love to find a pair of the 4.79 axle diffs or a complete pair of axles !

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link it plz

 

 

14.00 x 20 wheels and tyres will fit, see Hamptons website, they have a couple already done. Not sure how much quicker but certainly a bigger rolling radius.

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Would love to find a pair of the 4.79 axle diffs or a complete pair of axles !

 

I bought an entire rear bogie from DC thinking I could either use the complete axles or just the diffs. However the S26 refueller has a slightly heavier duty rear end with an extra couple of leaves in the springs and rectangular torque bars in place of the dog bones on the tractor which use different brackets on the axles and a different chassis cross member. The diffs, hub reductions and brakes were all interchangeable. The refueller tyres were also 12R22.5 in place of the 10R20 on the tractor and used a 5/8" wheel spacer to give clearance over the springs.

 

I also considered fitting the spare spring brake chambers to the trailing axle but the thought of the entire rear bogie locking up when running solo due to a valve or pipe failure made me think twice.

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1600X20 FIT Happy days need to do some arch mods,, but makes them real fast,,,,, the sldt could do 70mph,, too fast yes but the 350 rolls could pull it, so at 56mph the rpm was reasonable and mpg was very good, A chap tried it on a drops but didnt go through with it,, But i see no reason it would not work as the sldt,, see pics of 1600x20 on a drops,,

7636908364_8875538fee_z.jpg

22092011497.jpg

cars_013[1].jpg

cars_014[1].jpg

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I bought an entire rear bogie from DC thinking I could either use the complete axles or just the diffs. However the S26 refueller has a slightly heavier duty rear end with an extra couple of leaves in the springs and rectangular torque bars in place of the dog bones on the tractor which use different brackets on the axles and a different chassis cross member. The diffs, hub reductions and brakes were all interchangeable. The refueller tyres were also 12R22.5 in place of the 10R20 on the tractor and used a 5/8" wheel spacer to give clearance over the springs.

 

I also considered fitting the spare spring brake chambers to the trailing axle but the thought of the entire rear bogie locking up when running solo due to a valve or pipe failure made me think twice.

 

Where is the one you did now Mike ?

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