Naff Landrovers

At one time recently, he's also built 6 cylinder KH engines, based on the KH250 engines to produce a KH500-I6!! He also produced an absolute monster of banked engines, more cylinders than you could count (20-something I believe!). it moved under it's own power, I recall, but it wasn't a revvy thing due to exhaust and inlet designs. In fact, I heard it said that if it'd run for more than 10minutes it'd have seized through lack of cooling!!! Badger.

It is - 2 independent systems bolted together is not the same as one designed to be so - the latter set up you describe is *designed* to be that way, not cobbled together.

ok - I give up! Obvioulsy the entire railway (and for that matter, marine) industry has got it wrong for all these years!

I could go into the details of why the above paragraph is wrong, excpet for repeating again that it's the result of the compromise to make the system work at all, not a design goal. I could also bang on about the engine management ECU I worked on (Fitted to larger Volvo, almost all DAF, Dawoo, Hyundai and other Far Eastern truck and bus engines) which can so nearly balance each cylinder (configurable from 4 to 16 cylinders, any format) perfectly that any one cyinder can be identified as being weaker than the others (indicating some potential future failure, and whether is fuel or mechanical) and injectors can be switched off in a rotating cycle to imporve fuel efficiency when cruising without intriducing whip in the crank. Engine mangement has moved on a hell of a lot from the Rover V8 (hence it's demise) and carbs are well and truly consigned to history.

Richard

They would - but getting them to match is not possible, hence losses get introduced into the overall system.

The one running at 2900rpm will cause the one running at 3000rpm to think it needs to increase fueling to maintain its speed, hence the slower engine will viewed as a brake on the faster one and the system, now in imbalance, will be inefficient.

Obviously I don't!

Richard

The point is that no two engins *are* the same - the rated figures just a statement of roughly what can be expected, not a statement for that particular engine.

If one engine is not excactly the same as the other, one will try to drive the other, an the other will back off as it tries to maintain it's speed, putting a further load on the first one - there's you loss. Try turing an engine over by hand and see how much energy is required.

Richard

Nice in theory, but in reality all the losses in the system have accounted for. On paper, putting a winch cable through a snatch block and back to the winch doubles the pulling power of the winch. Are you suggesting that 100% efficiency is attainable?

If ignoring losses.

Richard

Power is force multiplied by velocity. The snatch block doubles the force whilst halving the speed. Hence power remains the same.

I don't actually see this - an engine doesn't see speed as a control variable does it, only load.

ELECTRICAL machines can often be mechanically connected as well as electrically, and give the expected o/p.

Not that I disagree with the general physical principle of Tanstaafl (look it up), but because I like a good fight.

Steve

...of course Effy is My Aunt who is Very Rude. So efficiency falls.

Steve

On or around Tue, 28 Jun 2005 10:30:17 +0000 (UTC), beamendsltd enlightened us thusly:

butbut, hangon. The railways sometimes use 4 or 5 power units on the front of a 3-mile-long train of wagons. If there's this law of diminishing returns as you say and to the extent you say, the 3rd, 4th etc. are not doing anything at all, which can't be right - they'd only use 2 locos.

In the question of 2 engines, I grant that you're never except by luck going to get all the power from both engines, but an engine running at 3000 rpm (say) with a fuel setting somewhere close to what it needs to run at that speed (but not exactly right) will be burning fuel and turning that fuel into mechanical energy. Suppose that the "master" engine is generating

70bhp, and the "slave" is running slightly underfuelled due to an imbalance of controls, and is only generating 60 bhp as a result - that 60 bhp is still there and still being used to propel the vehicle. Granting that the individual engines are not made to accurate enough specs that you can guarantee to synchronise them at more than 1 engine speed, I doubt that they'll differ by more than 10%, if suitably tuned.

I suppose you could, with such a system, run the proposed pair of engines - it'd doubtless not be viable. I assume it's running all cylinders individually.

Getting back to the point, though. Using a standard mechanical injection pump and spring-loaded injectors, it's highly likely that your ordinary

4-cylinder engine has imbalances which mean that not all of them contribute exactly to the running of the engine. However, the overall effect is more powerful than a 2-cylinder 1250cc engine.

On or around Tue, 28 Jun 2005 10:30:18 +0000 (UTC), beamendsltd enlightened us thusly:

Yeah, but then again, I'd be disappointed with a setup that gave an imbalance as big as 100 rpm in 3000. I'd expect to be able to get them closer than that.

too, there are these guys with multi-engine tractor-pulling machines - OK, that's partly for show. But even so, they must get some gain from it to be worth the effort, else why don't they simply fit a 14-litre Cummins with 4 turbos.

On or around Tue, 28 Jun 2005 12:06:10 +0100, Steve Taylor enlightened us thusly:

not exactly. more a mixture of the 2. The diesel pump contains a governor which responds to engine revs. Increased load decreases revs and the governor supplies more fuel, although it's also related to the position of the throttle. Driving a diesel (mechanical injection type, natch) with a fixed throttle however doesn't make it run at an exact RPM - the revs will drop under load and increase off-load, by a certain amount.

the thing is, you're not trying to get something for nothing - to use the full power available you have to supply twice as much fuel.

Whack a diff in there with the engines where the halfshafts would be and the power being delivered to the prop rather than being delivered by it, that would sort it. You'd have to modify the diff and make sure the engines drove the shafts in the right direction though!

Dax do/did a line in Lotus 7 replicas that have dual motorbike engines, one driving the front wheels, the other driving the rear. IIRC they had two motorbike gearboxes with the engine/gearbox combinations being mechanically unconnected, with speed/power matching being done by electronics. They're quite quick. IIRC they held the

0-60 dash world record and a few others until the Ultima GTR came along and monstered it using a basic 800kg car with space-frame chassis, 13-inch wide tyres and 650BHP carburetted Chevvy. MMMmmmm nice.

Well, I can't be doing the calcs, but when I bought my 110 it would just about do 85mph, now it will do 95 quite easily, so the characteristics of the engine have changed quite dramatically over the years - trying to match it with its original self would show a wild difference.

It's alot more than partly for show. I'm sure if the rules were "open" then they would just pop out and get one of those Russian 8x8's or a massive quarry machine - not very much of a crowd pleaser.

Richard

Exactly - that's why the South Wales iron ore trains had the three Class 37 locomotives (1750hp x 3) replaced with a single Class 56 -

4000hp!

I absolutely agree, though the loss is going to be more than 10% IMO, except that the hp from one is "fighting" against the other to try to obtan the desired speed/power from the its partner, so rather than driving the load the engines are trying to drive each other, hence the loss.

Obviously, unless the 4-cylinder was incredibly badly designed.

Richard

On or around Tue, 28 Jun 2005 16:06:27 +0000 (UTC), beamendsltd enlightened us thusly:

yeah, but what about the Australian ores trains and suchlike, with several locos, which IIRC they still do?

I suspect the class 56 replacing the class 37s might also be about running one more modern unit, with attendant savings in fuel consumption and maintenance.

On or around Tue, 28 Jun 2005 16:06:25 +0000 (UTC), beamendsltd enlightened us thusly:

well, aye. But you could fettle and tune the engines to similar state. Has yours done that spontaneously, or have you worked on it to achieve more power/torque?

On or around Tue, 28 Jun 2005 21:24:52 +0100, Austin Shackles enlightened us thusly:

Further to this I've been experimenting with NAD Ford this morning, which has a bosch mechanical pump on it.

With the throttle held steady (well, as steady as you can do with a foot pedal) at moderate revs, in 3rd, the speed varied with gradient anything between about 20 and 35. Giving it more throttle made it go faster, and backing off the throttle when on a downhill made it slow down.

The gist of all that is that while the governor in the pump does indeed vary the fuel supply, it doesn't do so with a very wide range - if the governor was capable of varying the fuel between max and min fuel levels, I'd expect it to sit at a single speed much more closely. Clearly, the governor is not able to shut the fuel supply off, and equally, it doesn't supply maximum fuel unless the revs drop quite a long way from the base settting, although past experience with these pumps on another engine leads me to believe that if you do something silly and get it to almost-stall, it does actually pull much harder than you might expect.

It might be that the governor is deliberately set up like that to make it more driveable, I suppose. In railway terms, you'd not need to do that; since in general they employ non-rigid transmission systems, mostly diesel-electric these days. With such systems, it'd probably be better to have a governor that responds fast and hard, so that when you increase the load, it supplies fuel ASAP to meet the demand. With a mechanical transmission, I suspect it'd prove difficult to drive it smoothly.