Thread: Torque curve ?

no thats drag racing...

I know its really really dangerous but theres just something about 2 men running down the road in womens clothing with someone cracking a whip at them thats just... well could you look away?

Originally Posted by Brian Hjelm

Torque is capacity to do work. Horsepower has time as a factor. Horsepower is work done in time taken. Put simply, a heavy truck that has high torque and low horsepower will have good startability and gradability, but wont pull three trailers up the dotted line at 110 k's. This is one of the reasons that American power trains took over the heavy truck market in Oz. The Europeans, particularly the Brits, could not understand the necessity for (then) 100kph cruising speeds.

Europe, and particularly Britain does not have the distances, but perhaps more significant is that at the tiem we are talking about Britain had a 30mph speed limit for commercial vehicles, so there was no need for high speed trucks.

John

When converting from a linear to a curvilinear system, torque is the curvilinear equivalent to force.

Work is force x distance. Move a weight to a higher/lower position - the work = weight x height. Doesn't matter whether the change in height is vertical or not.

Power is the time rate of work. More power is required to do the work in a shorter time.

Velocity is distance / time. So power can be expressed as force x velocity.

In a rotating (curvilinear) system power = torque x angular velocity. So power = torque x 2 pi x revs/time.

Take Dave's example of the 300 hp wrx. Remember that power = force x velocity.

Then the power would be the tractive force at the tyre contact patch x the velocity of the surface of the tyre.

Clearly, in the situation described it was not able to deliver/produce 300 hp. So talk of 300 hp was irrelevant.

It can only produce 300 hp when the force x velocity = 300 hp (the frictional and heat losses also have to be accounted for but that is another level of complexity).

Internal combustion engines are heat pumps - they need to pump air to do useful work.

When we talk of high performance engines, we are usually comparing power output vs engine displacement.

To get more power from a particular engine displacement we need it to pump more air. The way to do this is to increase the engine revs.

The important limit to this is the gas velocity - turbulence limits the velocity.

Now the gas velocity is determined by the piston speed.

Therefore the maximum engine revs is determined from the piston speed and stroke, which is limited by the gas velocity.

The only way to increase the engine revs (without increasing the piston speed) is to shorten the stroke.

So a short stroke engine can rev higher and pump more air, to produce more power.

Originally Posted by JDNSW

Europe, and particularly Britain does not have the distances, but perhaps more significant is that at the tiem we are talking about Britain had a 30mph speed limit for commercial vehicles, so there was no need for high speed trucks.

John

John, the Europeans were exporters. Their home markets were a small part of their production. They should have understood the different needs of different locations and applications. The poms in particular were paternalistic and patronising in their responses to requests for product improvement by "Colonials". Leyland Australia had gone from 40% of the heavy truck market (11+ tonnes) to under 8% in less than 10 years. We, at Truck & Bus Australia, pleaded with the poms for a 400hp prime mover that could haul a tri-axle semi-trailer grossing 40 tonnes at a cruising speed of 100kph and needed it right now. The response was that no-one needed a 400hp truck, and that such cruising speeds were dangerous. No matter that the Americans who had taken their market were producing trucks in australia with ,then, up to 475hp, now, up to 620! Leyland and other Euro makes were still sending trucks to Australia in the 70's with small oil bath air cleaners. A friend bought the first Scania, a 110 Super, in Oz to go into road train service and the distributor had to get approval from Sweden to remove the oil bath air cleaner and fit a Donaldson with high stack and pre-cleaner. He also had to send photos of a bull bar as they did not know what one was. He informed them that if they did not approve these two items then they would never sell another heavy prime mover in Australia. Even the American trucks with their advanced chassis, great power trains, needed considerable local input to adapt them to the rigours of Australian service. White, Kenworth, Mack and others did this and did it well to the point where they now own the heavy truck market in Australia.

What about Freightliner? Every second highway truck seems to be one of these.

do you mean freightliners or fleetliners?

I like the fleetlinger over the freightliner personally and they seem to be about the same density in the routes I travel....


I always cope heaps from them when Im slugging the R series,

At 600hp! I still recall driving an empty MR Isuzu I think it was flat stick up Mooney Mooney and being passed like I was standing still by a B-double.

No, the Freightliner is the one I meant, in particular the Argosy. It seems that most of the MC trucks that pass through here are either being pulled by a Freightliner Argosy or a Kenworth K104B type.

Originally Posted by Slunnie

At 600hp! I still recall driving an empty MR Isuzu I think it was flat stick up Mooney Mooney and being passed like I was standing still by a B-double.

No, the Freightliner is the one I meant, in particular the Argosy. It seems that most of the MC trucks that pass through here are either being pulled by a Freightliner Argosy or a Kenworth K104B type.

Freightliner seem to have made inroads into the fleet business on Eastern Seaboard line haul in recent years.

In road train, as opposed to B-double service, the pecking order has become Kenworth, Western Star, Mack, Freightliner. Not many Euros in outback road train service but Scania would be ahead of Volvo, with M-Benz a good way back.