Mate has just bought a 24volt ex mil petrol series with a shagged engine and wants to swap a diesel into it. The diesel is 12v. We were thinking that it may be easier to just convert the diesel engine to 24v rather than swapping the whole lot over. i assume that 24v glow plugs are no hassle, but can you get 24v diesel starters or run the existing one at 24v rather than 12?
The Dutch lightweights are diesel; 24 volt?
No direct experience of Land Rover, but many years ago I replaced an engine on a tractor with one from a truck. 24v starter motor on the truck engine replaced with the 12v motor from the tractor engine. Also swapped the alternator, of course. And the Land Rover diesel starter was pretty standard.
Remember that on a diesel of that era, the solenoid is part of the starter motor, not the seperate unit that the petrol engines used. So you would likely need some rearrangement of the wiring.
thats exactly what i thought of!. not sure about them though.
okay. so with a new solenoid might the 12v starter work fine on 24v? ive reasd that you can use 6v starters on 12v...
Diesel engines, with the high compression, need more power from the starter. I wouldn't bet on a 12v starter for a petrol engine.
The usual starter for diesel engines of the era has a solenoid unit attached, engaging the starter and closing the electrical contacts. So you need a longer lead from battery to solenoid terminal and also some way of making the connections to the rest of the electrics. There's also the power connection to activate the solenoid.
Finding a suitable 24v starter to replace a 12v starter on a Series engine might be tricky, because they're so old, but it's not impossible. When I ran a diesel Land Rover on the farm, the starter was pretty much the same as those on the tractors: different model numbers, but the same layout and assembly, and some parts the same. But nothing like the starter systems on petrol engines.
I wouldn't like to try hand-cranking a diesel.
Dutch Army used to have 24v Lightweights - friend of mine had one. I don't know exactly what the starter motor is but could find out if needed. He has sold the vehicle to another friend, who has put a 3.5 V8 in it.
The vehicle was originally used as a radio vehicle, which is why it was 24 volt. Until sold to second friend, it was kept as original as possible, though a roll cage was fitted for entering our local 4x4 competitions.
Cheers! Graham Carter Harare Zimbabwe
Tom Woods uttered summat worrerz funny about:
If the Engines are the same blocks and flywheel then why not use the 24v starter that is already on it?
Lee
Because a diesel starter is a very different (and far more powerful) animal than a petrol one.
But a 12volt petrol starter would be far more powerful if you put 24 volts up its arse :-)
Julian.
For a very short length of time.
Look on the bright side, you wouldn't need any glowplugs!
its the petrol-diesel issue that is the problem with that!
On or around Mon, 19 Mar 2007 09:33:24 +1200, EMB enlightened us thusly:
common practice in rallying, or used to be. 24V applied to 12V starter makes for reliable starting, if not long motor life.
I once invented an 8V system for a crappy botormike, extracted about 64W (est.) from the normally glow-worm 36W headlamp, the bulbs used to last about 2 months, but you could see where you were going and the indicators and such actually flashed credibly.
That was the drawback of the 'dynohub' as used on bikes wasnt it?
I can see why - When i drove my DIY windturbine (which is built round a dynohub!) off an electric motor i found in the garage I think it gave close to 100v on my multimeter!
On or around Mon, 19 Mar 2007 07:47:54 +0000, Tom Woods enlightened us thusly:
They're regulated by output, yes. The alternator on the botormike in question was permanent-magnet had a nominal output of 76W max, and had a cunning system whereby 4 out of 6 stator coils were switched out of circuit unless the headlamp were on. voltage was regulated by the battery. Adding an extra 2V in the form of some Cyclon cells let it run at 8V nominal instead of 6V nominal.
I've used 6v starters on 12v without problems. Starters and other electric motors are much more likely to be damaged by low than high voltage (within reason). My guess is that there would be no problems running the 12v diesel starter on 24v unless the engine is hard to start. The solenoid is probably the weak point, and it may be a good move to use relatively thin battery leads to give a bit of a voltage drop.
JD
If you get your 24volts from two 12volt batteries in series then it may be possible to take a centre tap from them to provide 12 volts just for the starter motor - and anything else that needs 12volts like the radio maybe?
Julian.
won't thin battery leads just be inclined to melt? ;)
I told him that i thought it would probably take the overvoltage as is. i suppose that if it doesnt when it gets rebuilt he could have it rebuilt as a 24v job.
yes, 24 volts will be gotten like that - its an ex-mil 24v landy.
I think he may already have a voltage dropper thing suitable for running his radio.
For the starter - can you get just 12v off one battery whilst it is still attached to the other one? I suppose that you could have the key operate a relay when in the crank position that split the batteries apart into 2 12v units - and it would just use one of them..
Provided the battery leads are not too thin they will not be a problem - I would suggest the sort of lead you would expect on smallish petrol engines. they will get warm, but should not get dangerously hot unless you crank it for a long time without it starting.
Getting even small loads from one of a pair of batteries is a recipe for short battery life (both of them - one ends up undercharged and the other overcharged). Getting starting currents from one battery is asking for very short battery life. There would be no reason to have relays, though, as you could simply connect the starter lead to the centre of the two batteries and everything else to the "top" of the two. But if you want to use relays, you could use two SPDT relays rated at the starting current, and parallel the batteries for starting. But these relays would probably cost as much as a 24v starter.
Another tack - there are probably still a few old style electrical places that will rewind a starter (and solenoid) to change the voltage. But they won't be cheap.
JD
The solenoids are a replacable component.
As I've said, the Series III diesel 12v starter was pretty well identical to the tractor starters I worked on, and the 24v starter I had experience of was the same. There's a metal strap from the solenoid to the motor terminal, and a couple of long thin bolts to hold the solenoid coil. On a tractor, the access was pretty good. On a Land Rover, a long reach. If parts are still available, no need to mess around with re- winding that.
Stop wittering about bodges. Contact a auto-electrical dealer who handles Lucas starters, and ask about a service-exchange, 12v for 24v.
You've already got a relay operated by the key, only it's called the solenoid! Just hook the main starter-battery cable (+ve?) to the bridging cable between the two batteries. Depending where its connected you may have to reroute the supply to the rest of the vehicle back to the top of the battery pair, as well as the alternator/charging circuit. Often these are taken from/to the starter end of the battery cable on the solenoid.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.