How can I determine whether a truck can climb a certain slope or not? 3

[hbogyt]

This is somewhat related to another thread of mine. Basically I want a truck to climb a 1 in 3 incline. How can I determine whether it has enough power to do that or not?

I don't even know where to start. I'm a civil engineer, and an undergraduate at that. This is such a special project that some of this specialised (for civil) knowledge is required.

Here's the exact configuration:

http://www.defence.gov.au/jlc/Documents/Cleaning Manual/91.pdf

 

[GregLocock]

You neeed to know the torque curve of the engine, details of all the gear ratios between the engine and the wheels, the rolling radius of the wheels and the total weight of the combination.

You need to know the loading on each driven wheel as well. Frankly I would guess that 1 in 3 is pushing it on normal truck tires since roughly half of the weight is on the trailer tires, so you need a mu from the tire >.67, truck tires don't go that high in my experience.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[gruntguru]

Any level of power will do - as long as you have low enough gearing and don't care how slowly the truck ascends.
As a first approximation, power = vertical velocity x mass x g = 1/3 x roadspeed x mass x g
Plug in the numbers for engine power, mass and "g" to calculate a roadspeed. Check the speed in the lowest gear at max engine power rpm. If this is lower than the calculated roadspeed, you have enough power and gear-reduction to climb a 1 in 3 grade. Most trucks have very low gearing available.

As Greg said - your problem is most likely going to be traction.

je suis charlie

 

[enginesrus]

Most important is what the surface is made of that it will be traveling on?
18.4 degree slope, what is the speed you wish to do it at? What is the vehicle weight?
It can be done with low power, if speed is not important.
The link didn't show much for specifications. To climb the hill and depending on the surface material and conditions
it will need as much weight on the truck as possible if pulling a trailer, that is accomplished by loading the load as close to the hitch point as possible. If the road going up the hill is not very long and conditions permit a nice high speed run at it will get the job done even with bad traction. So what are the variables?
And like everything in engineering go test it.

 

[hbogyt]

Material will be crushed rock and concrete.

Tank weighs 60 tons. Not sure about the truck. The trailer is indirectly connect to the prime mover via a dolly converter. So I'm not sure if any of the tank's weight can be transferred to the prime mover.

The truck will start from 0 speed, so unfortunately a high speed run is out of the question.

 

[GregLocock]

Based on the little we know, the traction wheels will slip. The ADF aren't entirely clueless when it comes to this stuff, it is, after all, high school physics. Ask them for data.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[3DDave]

This is why, on the M1000 HETS the trailer is a semi-trailer and is designed to transfer load to the tractor traction wheels. These home-grown tank trailers don't have the mobility. They also don't have the cost, but you get what you pay for.

 

[hbogyt]

I'm a bit confused. the M1000 HETS looks similar to the commercial trailer in my case. How does it transfer load to the tractor when mine can't.

 

[3DDave]

It has a gooseneck directly to the truck instead of a dolly that prevents that load transfer.

The difference between a semi-trailer and a trailer is that a trailer carries all the weight of the payload, like a children's wagon does. A semi-trailer is supported by the tractor on one end.

 

[hbogyt]

Can the dolly transfer any weight?

I mean in my case, the prime mover tows a dolly that looks like a mini semi trailer via a gooseneck, which in turn tows a semi-trailer via a gooseneck.

 

[3DDave]

Remove the tractor and what is left is almost a trailer. Just because that trailer can be disassembled doesn't make a difference.

It looks like the dolly transfers no more than 25% of the 5th wheel load from the base trailer. If the load is 50/50 on the trailer wheels to trailer 5th wheel, then only 13% is put on the tractor. If that was the only amount for traction, then with 100% coefficient of friction it would slip on a 13% slope; 1:8.

 

[chicopee]

One more thought is that if the tractor starts doing a wheelie during its ascent then its rear axle will have more traction and perhaps sustain the climb but then you have no steering.

 

[Gary_321]

I was very much involved in the UK version of what you are doing.

If you look at the last two UK solutions, Scammell Commander and HET, you will see that the tractor unit has a bonnet and the engine is forward of the cab. There is a very good reason for this.

When contractor vehicles were used to tow the Commander trailers, they used tractor units like yours. They were doing wheelies going up the hill out of one of our camps. The steering wheels were off the ground. THIS WILL BE YOUR MAIN PROBLEM.

Our solution was to contract the requirement. If you are the contractor, there are truck simulators available online. These may help you.