World's Fastest Diesel
World's Fastest Diesel
(OP)
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






RE: World's Fastest Diesel
RE: World's Fastest Diesel
RE: World's Fastest Diesel
Hmm, 5.2 Bar, that must give a prety high Pmax!
RE: World's Fastest Diesel
RE: World's Fastest Diesel
RE: World's Fastest Diesel
Tony
Tony Athens
http://www.sbmar.com
RE: World's Fastest Diesel
RE: World's Fastest Diesel
With a CdA of 0.15 m2 and assuming air density of 1.2 kg/m3, they will be effectively hitting about 0.18 kg of air for every metre travelled.
So every second the JCB hits 0.18*180 = 32.4 kg of air with a kinetic energy of 1/2*m*v*v of (1/2) * 32.4 * 180 * 180 = 524880 Joules.
That is 524 kW required to overcome air resistance.
They are using a 560 kW engine.
So what is holding the thing back from getting to 400 MPH?
RE: World's Fastest Diesel
Besides air density at this altitude is probably less than 1.08 kg/m^3 (since it is pretty hot up there it might even reach 1 kg/m^3) and RAM air is already significant at these speeds (over 10% intake pressure increase), so according to your calculation it should even be faster.
RE: World's Fastest Diesel
Very impressive!
Ken
RE: World's Fastest Diesel
"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams
RE: World's Fastest Diesel
Nope. They used two of them!
The limiting factor is tyres. They were only rated to 350 mph. The car is faster than its tyres.
For those who want some insight into the engine, try this:
http://
RE: World's Fastest Diesel
RE: World's Fastest Diesel
It looks sleek, but it's way on the heavy side. There are 400+ MPH tires around, but perhaps not for that load.
RE: World's Fastest Diesel
just a strong steel wheels
the driver is Andi Green who drove the SSC breaking the sound speed few years ago , he is a pilot in UK army & was chosen for the better training in controlling vehicles with LIFT
. just a tenth of degree of nose going up could
be disaster.
RE: World's Fastest Diesel
You are right about the friction thing - it needs proper tyres. And even so there's apparently some kind of "wheel-spin-ometer" in the cab too to monitor what's going on.
w.r.t. all-wheel drive, it already is. One engine for the front; one for the back.
RE: World's Fastest Diesel
SSC was an upside-down plane with forward force coming from those jet engines. Dieselmax needed force through it's wheels. Hence the requirement for good tyres.
RE: World's Fastest Diesel
tyres are limited in their spin velocity .
spin it over the limit and it'll expand by the heat to much and eventually will explode
RE: World's Fastest Diesel
Are you seriously suggesting that traction is irrelevant to drive line types where one transmits power through the wheels and one does not, or are you suggesting that there is no difference in the traction of rubber vs steel, or are you suggesting that on a traction limited performance, that traction can be further reduced.
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RE: World's Fastest Diesel
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: World's Fastest Diesel
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.
RE: World's Fastest Diesel
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.
RE: World's Fastest Diesel
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.
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RE: World's Fastest Diesel
RE: World's Fastest Diesel
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?
RE: World's Fastest Diesel
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.
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RE: World's Fastest Diesel
Ken
RE: World's Fastest Diesel
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
RE: World's Fastest Diesel
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.
RE: World's Fastest Diesel
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
RE: World's Fastest Diesel
RE: World's Fastest Diesel
RE: World's Fastest Diesel
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.
RE: World's Fastest Diesel
RE: World's Fastest Diesel
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.
RE: World's Fastest Diesel
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.
RE: World's Fastest Diesel
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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RE: World's Fastest Diesel
Rumour is that it was a high speed tyre blow-out causing a rollover.
PW