Re: [MV] Re: Underpowered UNIMOG

Brent Boxall (bboxall@chattanooga.net)
Tue, 27 Jan 1998 21:42:37 -0500

It is my opinion that the horsepower of the truck is not really what makes it go
but the TORQUE. Here is an example:
*An extremely HIGH performance tractor trailer in the US would have a 525 hp (1850
ft-lbs torque) Cummins in it. These trucks run at 40 tons total gross so that
would be only 13.2 hp per ton. This is less that my M35 or your Unimog but this
truck can pull a 5% grade at 70+ mph FULLY LOADED. I don't know about your Unimog
but if this tractor trailer passed my M35 on the same 5% grade the speed difference
would probably suck the mirrors off my M35.
(As a side note on diesel efficiency this truck will get 6-8 miles / gallon running
fully loaded)
(see http://www.cummins.com/onhigh/high.html)

All kidding aside, as a mechanical engineer I can promise you that torque is what
makes trucks perform. Think about it this way: if I took a 1.1 liter 140 hp
motorcycle engine and put it in my M35 it would improve my hp / ton rating slightly
but would the truck climb hills better??

I have no idea what the Unimog's torque specifications are but my M35A2 has 330
ft-lb of torque. My 3/4 ton Dodge Ram w/Cummins as 180 hp & 450 ft-lb of torque.
(I wish I had an extra 6 liter Cummins to put in the M35)

What is the torque spec for the Unimog?

Also, the payload specs for the M35A2 are: 10,000 lb off road or 20,000 lb
highway plus 10,000 gross trailer weight.

Sorry for the long winded response,
Brent Boxall

Andreas Mehlhorn wrote:

> Brent Boxall schrieb:
> > Here is my 2 cents worth on the Unimog:
> > My personal experience with an AM General 2.5 ton 6x6 is that you NEED power
> > in off road situations. Here in the North Georgia Mountains if you are
> > climbing a ridge on a dirt road is takes all 134 HP to keep the 13,000 lbs.
> > unloaded truck climbing at a good 20-25 mph on a steep grade. I don't think
> > that less power would be acceptable especially with cargo load and a trailer.
> >
> > Brent Boxall
> >
> Dear Brent,
>
> If your AM Genral 6x6 offers 134 HP and has an unloaded weight of 13.000 lbs,
> you have a power/weight ratio of 22,8 hp per metric ton unloaded and 16 hp/ton
> with 2.5 tons payload.
>
> The "underpowered" UNIMOG offers 26,7 hp/ton unloaded and 17,8 hp/ton with
> 1.5 tons payload. So it has more power per ton than your vehicle.
>
> It is true that the Mercedes-Benz 2,2 litre petrol engine of the UNIMOG
> with its low torque and high revs is not ideal for an off road vehicle.
> But in the 60s the Bundeswehr prefered petrol engines. They were afraid
> of handling diesel fuel at low temperatures. That was stupid, because the
> Russians used diesel since WW2 in their tanks and it worked well, even at
> Sibirian temperatures. Note that the 404 UNIMOG is a vehicle desgined in
> the mid 50s. At that time trucks had 6 hp per ton fully loaded with trailer.
>
> Most civilian UNIMOGS came with diesel engines, which offers better torque
> at lower revs.
>
> Regards
> Andreas (ex radio operator on UNIMOG and M113)
>
>
>
> =
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