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David Gentleman

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Postby David Gentleman » Fri Jul 06, 2007 11:22 am

Martin Faulks wrote:
Stunned Monkey wrote:The general consensus among both Lotus and Alpine people I've spoken to reckon on 60hp loss in a UN1. We -know- it


I'm struggling with this figure - that's 45 x 1kW electric fires burning in your gearbox, because if that's losses it can only come out in heat. Ok lets allow 5 x 1kW fires at the wheels for bearing losses and one each for the CV joints, but that's still a xxxx load of fires in the gearbox!!! Some would say you would have a hard time fitting them there fires in there :lol:

:


And noise, vibration, pumping losses in the viscosity of the oil, the fact that the oil absorbs the heat.. energy taken up by spinning larger heavier wheels and tyres, and odd sticky calipers.

Don't think of it as the heat of all those fires, but the fact that a whole gearbox casing can be hot to the touch after a hard run. Now it DOES take a lot of energy to heat something that large up so quickly.

Mitsubishi Evos\ Sunny GTi'R's (4wd) lose over 100bhp through the drivetrain...

I don't claim to know anything about the calculations you quoted, but does power loss always relate to heat? I mean, if the 30bhp gearbox loss, has equated to 680 degrees, then how come an engine making say 800 degrees exhaust gas temps could made 250bhp?
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Postby Stunned Monkey » Fri Jul 06, 2007 11:43 am

David Gentleman wrote:
I don't claim to know anything about the calculations you quoted, but does power loss always relate to heat? I mean, if the 30bhp gearbox loss, has equated to 680 degrees, then how come an engine making say 800 degrees exhaust gas temps could made 250bhp?


Energy cannot be created or destroyed, it can only be transferred...

And there are only so many ways of transferring energy

Kinetic (movement)
Heat
Sound
Light
...and a few other irrelevant ones for this example.

No energy transfer is 100% efficient, and the transmission is a great example, but while it loses a small amount of energy to sound (and I doubt much light!) the lion's share of the energy losses are to heat.

An engine's inefficiencies are lost largely as heat, but mostly via the radiator. Most of the sound lost is converted to heat in the exhaust and combined with wasted combustion heat. Some light in the infra-red spectrum, exp when working very hard, maybe the odd bit of visible light.

I don't quite understnd MF's equation....? If you're losing 43hp that's 43 x 746 = 32kW and that does seem like a lot but some of that will be conducted to the engine, much will be transferred to the surrounding air... but of course it's not just the tranny in question but the wheels and tyres..... I'm speculating here - MF am I right?
Martin - PRV Tinkerererer
www.delorean.co.uk
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Postby David Gentleman » Fri Jul 06, 2007 12:08 pm

Stunned Monkey wrote:
I don't quite understnd MF's equation....? If you're losing 43hp that's 43 x 746 = 32kW and that does seem like a lot but some of that will be conducted to the engine, much will be transferred to the surrounding air... but of course it's not just the tranny in question but the wheels and tyres..... I'm speculating here - MF am I right?


Its being transfered to everything, box, diff, shafts, hubs, bearings, wheels, tyres, and most importantly, the rollers!
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Postby Stunned Monkey » Fri Jul 06, 2007 4:56 pm

And in a smooth parallel under the heading of "why I don't like superchargers" - isn't it something like 250hp is technically "lost" in turning the supercharger on the McMerc?

I do remember that 20% of the power developed by Concorde's engines went into the AC system to keep the cabin cool...

Yep, defo a friday feeling. Just dropped a gearbox on a DeLorean in under 2 hours, wasn't really trying that hard, was quite surprised Steve Wright was still on when I'd finished....! Anyway, rambling....
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Postby Stunned Monkey » Fri Jul 06, 2007 5:02 pm

Martin Faulks wrote:
I got stuffed by my over enthusiasm the other day, really suckered. I had been working on some sensor technologies for a company developing a special diesel system, can't say anymore about it, but it needed very high temperatures and pressures... I spent ages working on the system control etc etc (I get paid by selling the sensor technologies not the upfront engineering design), and missed the obvious - it would need a trailer behind the truck to carry the batteries for the heaters - duh!!! I got really annoyed with myself for getting pulled along by the enthusiasm and not the practicality... I should have said "umm nice idea, come back when you have made one" laugh!


Reminds me of the time I was looking at keeping our drive motors in the robot cool with the use of a hoffing great peltier heat pump... (two 5kg 1200W S2 motors with an S2 rating of 2 mins... they got quite.... warm!)
Martin - PRV Tinkerererer
www.delorean.co.uk
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Postby darrenbiggs » Fri Jul 06, 2007 6:31 pm

Martin Faulks wrote:He's got the complete robot from Tomb Raider 1, the thing AJ fights at the beginning of the film, love to get my hands on that 8) Needs putting back together, in crates.... how much fun would that be!!! Move over Mr. Brown.... LOL ... what TAX bill was that???? :twisted:


Is that love to get my hands on the robot or love to get my hands on Angelina Jolie? I know which gets my vote :wink:
I'm just here for the gasoline.
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