What size of wheels do I need for a 80,000 lbs military vehicle off road?

[Peter Dow]

Hi I am looking for some off road experts to give me some hints as to the size of wheel to draw for my concept design of a military vehicle.

It is OK I don't have to build one, just draw it, but right now, my wheels look far too small.

It is a 50,000 lbs (22,700 Kg) vehicle with a 30,000 lbs (13,600 Kg) trailer, total 80,000 lbs (36,300 Kgs). It is that heavy because of the anti-mine armour it has got.

The front 50,000 lbs is about the size of a Mastiff 2.



Now that's got 6 wheels and they look like they are about 3 feet in diameter (1 yard / metre) maybe. I am not sure if that is really enough wheel and tyre to get a grip in the sand, dirt or soft wet soil, (mud!  :D) not for 50,000 lbs or 25 short (US) tons for the Mastiff 2.

My machine is 80,000 lbs all up with the trailer and I might need more wheels as well as bigger wheels. What do you think, mud experts?


The Mastiff 2's wheels are fine for the roads of Iraq but what about something softer?

When I come to my concept design drawing, I can afford bigger rear (or middle) wheels because they don't need to turn. The front and trailer wheels need to be smaller and the same size because they both steer.

This is for Afghanistan so it is not all mud by any means but the roads are dirt roads pretty much "off road" really.

So see what you think if you would like to venture an opinion as to what size of wheels to draw. I just know the wheels I have drawn just now are too small.



Introducing HUMPBAC - an armoured personnel carrier with a connecting doorway from the rear of the vehicle to walk through into the armoured passenger trailer. Tickets please!  :D

HUMPBAC
Hinged Under-floor-Mine-Protection Battle-ready Armoured-personnel Carrier
Copyright

[stevethedent]

Peter, you really need to get out more! LOL.   :shock:

[sMUDge]

Interesting project. 
Go back to basics though, what will this vehicle be used for  :-k  Having served in all the places you mention, I see no job for it.  It's too big as a fighting vehicle, no load space so not a logistics vehicle, perhaps as a Force Protection vehicle  :-k   
Though currently in Afghan, the Taliban seem to be shifting from IED to SRSAF, so no real use there either. 
You say personnel carrier, but what formation?  18 blokes fully bombed up wouldn't fit, 10+ kit would, so a section strength vehicle, but then bin the seats in the trailer part & make that storage for the blokes kit  :clap:

Looks good though mate  :dance:

[dxmedia]

20" rims with probably 44" tyres (12.00's (12.00r20) are common millitary size)

I say that cus I've got a set at the bottom of the garden ;)

The millitary stick to generally the same wheel and tyre size so that they can be interchanged between vehicles in case of issues.

[Grumpy]

Your gonna need more wheels it's going to ground it's self quite easily

[Peter Dow]

Interesting project.  
Go back to basics though, what will this vehicle be used for  :-k  Having served in all the places you mention, I see no job for it.  It's too big as a fighting vehicle, no load space so not a logistics vehicle, perhaps as a Force Protection vehicle  :-k  
Though currently in Afghan, the Taliban seem to be shifting from IED to SRSAF, so no real use there either.  
You say personnel carrier, but what formation?  18 blokes fully bombed up wouldn't fit, 10+ kit would, so a section strength vehicle, but then bin the seats in the trailer part & make that storage for the blokes kit  :clap:

Looks good though mate  :dance:

Thanks.

The basic idea was a MRAP-type vehicle, like the Mastiff 2 but specialised for Afghanistan. The roads are really bad in Afghanistan and those vehicles that did well in Iraq, in terms of protecting people from mines and IEDs, are struggling with the "roads" such as they are.

So it seems to me we need the same heavy-weight armour for the IEDs (and if our forces stop driving about in heavy armour the Taliban will go right back to using IEDs to get the kills) but we also need off road ability. Which means we need to look at the tyres - more tyres, maybe bigger tyres.

While I was designing for off road and stability, I thought up a few new ideas as well - telescopic rear axle - rotation about the spot - armoured trailer - remote weapons stations on the roof - and so on.

Now the fact is whether you or I see a need for the MRAPs in Afghanistan - they are using them - and rolling over, getting stuck, and that leaves them vulnerable. So we need better vehicles.

Maybe something more like the Stryker would be better for getting around in Afghanistan - it already has got loads of wheels?



Well as for room for kit as well, take the Mastiff 2, advertised as 2 crew + 8 passengers. Like 8 soldiers plus kit do you reckon? Or do they have to put all their kit in another truck?

The HUMPBAC tries to make more room for passengers by extending the driver cabin over the front axle in a "Cab over" configuration.

So I think 11 is fair for the front section and 7 for the trailer, based on the size of the Mastiff 2 anyway.

How much kit does an infantry man need - "fully bombed up" as you put it?

The thing is advertising the HUMPBAC concept as only 10 plus kit they will wonder how come you have a bigger vehicle but can't carry more?

Plus anyway I need to keep at least one guy in the trailer to operate the tail gun.

[Peter Dow]

20" rims with probably 44" tyres (12.00's (12.00r20) are common millitary size)

I say that cus I've got a set at the bottom of the garden ;)

The millitary stick to generally the same wheel and tyre size so that they can be interchanged between vehicles in case of issues.

Thanks . With your clue I found a manufacturers data sheet for tyres - Continental.

The 12.00 R 20 they say is 1122 mm or 44.2 inches outer (diameter?) which has a maximum load 8,000 Kg per axle.
They also do a 14.00 R 20 (has a "MIL" pattern code) 1238 or 48.7 inches which has a maximum load of 10,000 Kg per axle.

You can also get about double those values if you use a double tyre fitment, which must be 4 tyres per axle instead of just the two.

So it looks like you can get more out of the 14.00 R 20 and maybe that is quite a common military size too?

[Peter Dow]

 

Your gonna need more wheels it's going to ground it's self quite easily

Thanks for the tip. This is what I feared.

What do you mean ground? Do you mean get stuck? Well that is what I am asking about off road.

You see the load is one thing.

80,000 lbs is 36287 Kgs. So that is actually too much for 3 axles even using the biiger 14.00 R 20 tyres, unless I was to use double tyre fitment - not sure how easy that is for wheels that steer - seen it on rear drive wheels.

So I am thinking more of 5 axles now, 3 on the front vehicle and 2 on the trailer, just for the load.

5 axles even at 8,000 Kg per axle for the  12.00 R 20 tyre that would take the load up to a maximum of 40,000 Kg - more than the HUMPBAC needs.

So 5 axles looks better for the load.

But what I am really wondering is how much weight can you put on a soft off road surface per axle or per wheel?

When the tyre company says "8000 Kg" per axle, that is on a road. If you are in mud the tyre would be fine, it would just bog down and you would get stuck, right?

So come on, you guys are the experts on mud and off road. How much weight could you put on a 12.00 R 20 on mud or sand or dirt or whatever and still drive OK?

I suppose it depends on the mud, on the sand or the dirt - how wet it is, how loose and so on? Can you give me an estimate?

[dxmedia]

20" rims with probably 44" tyres (12.00's (12.00r20) are common millitary size)

I say that cus I've got a set at the bottom of the garden ;)

The millitary stick to generally the same wheel and tyre size so that they can be interchanged between vehicles in case of issues.

Thanks . With your clue I found a manufacturers data sheet for tyres - Continental.

The 12.00 R 20 they say is 1122 mm or 44.2 inches outer (diameter?) which has a maximum load 8,000 Kg per axle.
They also do a 14.00 R 20 (has a "MIL" pattern code) 1238 or 48.7 inches which has a maximum load of 10,000 Kg per axle.

You can also get about double those values if you use a double tyre fitment, which must be 4 tyres per axle instead of just the two.

So it looks like you can get more out of the 14.00 R 20 and maybe that is quite a common military size too?

Close but no cigar ;)

For twin tyres think of about 1.5X the stamped weight rather than 2X, think it's to do with how the side walls buldge when they are inflated and under load - and to stop the bulges touching (causes heat and blow outs).

If I can be arsed later - I've some G388's which are commercial offroad spec tyres, I'll have a look at what's on the sidewall of them for a comparison to the continentals - they are goodyears.

[Grumpy]

At present your vehicle could not go over a hump as the chassis would rest on the hump between the wheels and ground itself and result in loss of traction to the driving wheels and would be a sitting duck , shorten the vehicle or add more wheels, simples!

[dxmedia]

Have a look on youtube for a tatra 813 (god I love those things), it's got 4 axles but split into two pairs. Both pairs sit on bogeys so work indipendently of the chassis. They will travel over any terrain - Mean ANY :D

There's a great review on difflock of driving one - basically if you don't get over the top of the hill first time, back up and try again. Once you've flattened the hill you'll be able to carry on ;) :D

[dxmedia]

Your gonna need more wheels it's going to ground it's self quite easily

Apparently russia disagree with you ;)



That'll be a Baz5921 missile launcher from the cold war.

[Skibum346]

Plus anyway I need to keep at least one guy in the trailer to operate the tail gun.

Think you need to read up more on the weapon stations you've shown in your diagram. They areremote weapon stations. That means the "gunner" can be anywhere in the vehicle Come to think of it... in this day and age he doesn't even need to be IN the vehicle!

[tack43]

Interesting project. As said above an 8x8 configuration simular to the Fuchs would be better. Can't remember what size they are but the wheels and tyres from a Leyland-Daf DROPS may be what you are looking for. The DROPS is an 8 wheeler with a bridging weight of 32000 kg or over 55000 kg depending on trailer.

Hope this helps

Rich

[wormster]

Put some armor on the propshafts please. It looks kinda vunerable at the moment.

[Disco Matt]

I do like the Tatra 8x8, a very clever chassis design. Basically the chassis is a girder with the engine inside and suspension units, body, etc hanging from it. As a result they can be reconfigured easily and repaired in the event of damage. They will also go absolutely anywhere!

I suspect that Baz missile launcher was intended for made-up roads (even just hard packed gravel or mud). The Tatra's magic comes at least in part due to the articulation of the individual suspension units, it doesn't look as though the Baz could flex much.

Also look at the Scammell Explorer (and their other triple axle ballast tractor units) - again, a very capable chassis design which you can learn a lot from.