World's Fastest Diesel 1

[Fabrico]

Anyone notice the new Diesel Land Speed Record of 350 mph (563 kph) just set by a Andy Green from England? There's some amazing numbers, including 10.5:1 compression.

http://www.jcbdieselmax.com/html/home.php

 

[GregLocock]

Interetsing. I wonder if they deliberately designed it heavy so as to improve the traction torque available?



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[levil]

Therese a relevance between traction & drive line types.
BUT
traction of rubber will drop (as the temperature rise) in high velocities , while the steel wheels (with the lesser traction) wont changed much or deform or explode.

at the end, the two drive line types spins wheels.

once upon a time there was the mighty Lamborghini Countach the calculated top speed of the 1984 monster was 290 km/hour but at that speed the tyres & the air trapped in it, got so hot that it expand and made the final ratio higher, so the top speed were eventualy 295 Km/Hour.

 

[SomptingGuy]

levil,

Draw a free-body diagram of a vehicle at its terminal speed. You'll see that the tractive effort at the wheels has to match the air drag. If steel wheels can't provide enough tractive effort to overcome a 350 mph head wind, they can't be used.

Also bear in mind that the runways are limited in length, so acceleration is also an issue. Another reason to favour high-grip tyres.

These people aren't stupid.

 

[patprimmer]

Wow

A whole 290 kph. That's slightly over half the speed we are talking about, and 30 kph faster than the Holden panel van I used as a daily driver back in the late 70s.

It did 250kph in good old "V" rated Michelin XMURs on public highways in the Aussie outback. I never checked tyre growth or overall gearing change, or slip, as I expect the torque converter would have made a lot more than the 1.5% or so you are talking about. I never calibrated the the speedo either, but did check times over the 400 kilometres between fuel stops.

Each rubber compound has it's optimum temperature for maximum traction, so it is a bit presumptuous to predict a decrease due to temperature increase without knowing the actual and optimum temperatures.

What has increased diameter due to pressure build up or centrifugal force got to do with traction.

Regards

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[levil]

You probably right, i don't know wheres lie the speed limit for tyres, so 350 mph is below that limit

 

[globi5]

Couldn't traction be improved with profiled or spiked steel wheels? The wheels don't spin faster than a gasturbine, so it shouldn't break apart. Also wheelwells could be lined with Kevlar in case a spike gets lost.
If traction is the major issue, why don't they make it even heavier to increase tire friction and overcome air friction? Or does acceleration matter as well?

 

[patprimmer]

They have a limited length of track, so acceleration definitely matters.

Spikes penetrating the salt might soak up power, cut up the track and thereby earning the wrath of officials and set up vibrations in the chassis.

I don't know if they use aramid fibre reinforced solid tyres, but these should be stronger.

Regards

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[kenre]

I recall reading about another land speed vehicle that used solid Aluminium wheels. Fairly certain it was a jet powered machine, so wheels just followed along. they also had sensors for the scrutineers to check to see that the wheels were always in contact with the ground.

Ken

 

[RobWard]

I read with Thrust SSC that the wheel design was quite critical and had to work correctly with the surface (sand or salt). They found that after their supersonic runs that the wheels weren't rotating as fast as they should have, but I don't know if they ever found out why.
They also said that given the thrust available they should in theory have been able to go faster, and, if I recall correctly, the shock wave was ploughing up the surface 6" or so of desert 100's of feet wide.
Give that the JCB had localised supersonic airflow it is conceivable that small scale effects similar to the SSC experienced may be occuring.

"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams

 

[PEW]

I got to see the project and its UK testing to some extent as I work for JCB (flying folks about).

The project was designed to publicise the new JCB444 diesel engine. This engine was originally designed to put out about 140 bhp for excavators / earth movers but the two-stage turbochargers put this up to 750 bhp.

The low CR was required because of the very high boost pressures being used to obtain the output. The low CR meant that the engine had to be warmed to working temperature before trying to start it. Interestingly, once the car was up to speed and on boost there was hardly a trace of exhaust smoke.

Regarding durability, the engines were only required to run for about 20 minutes to take the record, as it happened they ran one for over 20 hours during testing.

BTW, Andy Green is a Wing Commander, Royal Air Force and not in the "UK Army"!

I was privileged to speak at some length with Ron Ayers, who designed the aerodynamics of the car. Ron also designed the Thrust SSC car and also helped design the Bloodhound missiles that helped protect Britain's airspace in the Cold War, so he goes back a very long way. I discussed the tyres with him. He confirmed they were the limiting factor on speed. Goodyear only rated them to 300 mph. JCB had them load tested up to 350 mph and it was decided that should be the maximum speed attempted. It was more important to safely break the record (by 125mph, as it was) than to go all out and risk the car and the driver! Bear in mind the record was taken in 5th gear, it does have 6 gears.

Rubber tyres were needed for traction on DieselMax because all the drive goes through them, unlike on Thrust SSC, where the jet thrust pushed the car along and straight line traction was less critical. BTW, the tyres were only 15" x 5.00". Ron Ayers told me they had to withstand the equivalent of up to 35,000 rotational "G" ....

The guys designed and built the car and took the record in 18 months from start to finish. The car didn't even exist until April this year. I have been told the entire project cost about the same amount that sponsorship of a Formula 1 car racing team for a season would cost.... but the DieselMax car will be there for all time.

 

[Fabrico]

Interesting PEW.

The tire limits must have to do with weight. There are other wheel driven cars that have gone way past 350 MPH. Don Vesco's 458 MPH Turbinator has 24.5" x 7.5" x 16" Mickey Thompson tires rated for "730 MPH".

http://www.teamvesco.com/carspecs.htm

 

[PEW]

Been discussing the car today with someone very much in the know. I asked if they were planning a further record run. The answer was yes, possibly, subject to tyres. Next time they even might put it into 6th gear!

 

[ivymike]

There's a chance I'll get to see that thing on display in the Chicago burbs in a few weeks - if I can get the day off work.

 

[crysta1c1ear]

Yes, if the limit is the bodywork and wheels, they could just try to squeeze their diesel engines into the vehicle above and they should be good for another 100 MPH.

I personally don't see weight as being a problem. Some tiny wings could be made to create some lift and reduce weight by whatever amount you wanted. So I think weight on the tyres is a bogus argument too, if the vehicle is designed ok.

 

[ivymike]

tiny wings with a low L/D ratio... doesn't sound all that appealing to me. Long, narrow wings with high L/D also don't sound so appealing.

 

[PEW]

British engine in an American chassis?

Hmmm....might work, sounds familiar!

Ah yes, I think they called a previous project the P-51 D Mustang and it seemed to fly quite well - laminar flow wings on that chassis though... ;-)

Seriously, I think if you see how closely the engines and ancilliaries are shoe-horned in to the DieselMax chassis, you would realise it could never be done.

 

[Mimbrogno]

I don't know how fast this attempt will get, but I think I might try getting 400mph on diesel a different way. For one thing, there's an engine of ideal size, weight, and 1800+ hp that's been around for some 65 years already. It's powered aircraft to over 500mph, and it was one of the more prolific engines of WWII. Too bad today they are pretty hard to come by, since nobody's made them since BF-109's went out of production.

As for tires, I myself would employ a ducted fan to propel the car. A propeller might work too, but I would worry about having the blades so close to the ground, and the turbulance they could create.

That's my two cent's anyway....

Matthew Imbrogno
Mechanical Vollenteer - Arizona Railway Museum.

 

[patprimmer]

I think class rules call for "all power to be transmitted through the wheels", hence the need for good traction to accelerate to speed and to overcome air resistance at speed.

Improved aerodynamics and reduced weight both reduce the need for traction, but reduced weight also reduces traction, but reduces load and therefore heat build up in tyres.

Regards

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[PEW]

A reminder tonight of how potentially dangerous this type of thing can be. A well-known TV presenter, Richard Hammond, of UK's "Top Gear" programme has been very seriously injured in a crash of a jet powered car at RAF Elvington in Yorkshire (by coincidence an airfield where I flew during my RAF jet training).

Rumour is that it was a high speed tyre blow-out causing a rollover.

PW