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Using 240v to start an engine?

hillbillyracer - 4/9/10 at 12:04 PM

Not something you'd normally want having to need access to the mains just to start your engine is it?! I have a generator that supplies 3ph power for my workshop, it's the power unit from a large fridge trailer with a 4cyl Kubota diesel engine & at the moment it lives in the workshop & is the biggest single thing preventing me getting my car in to make progress with the build.
As it can stand for a few weeks at a time without starting it's a pain in the erse having to keep sorting/charging a battery for it & as it's never really going to move once sited outside it'd be really handy to be able to just hit a button in the workshop to fire it up.
Now your average 240v motor is'nt built to do this short burst of high load sort of thing that a 12v starter is so I'm tiring to work out what it would take & if it's even practical.
Gettin it to drive the engine is something I could engineer if a suitable motor were available.

mangogrooveworkshop - 4/9/10 at 12:11 PM

Schiples

get a trickle charger to keep the battery topped up and that's you answer

hillbillyracer - 4/9/10 at 12:19 PM

Yep, that's the original plan & a likely course but I'm just looking into the alternative.
It would ironicly mean I could'nt start the genny in a power cut but it aint for mains back up anyway, I've got a 5kva single phase for that.

dan8400 - 4/9/10 at 12:26 PM

quote:
Originally posted by mangogrooveworkshop
Schiples

Pissed Meerkat?

Dan

SteveWalker - 4/9/10 at 01:17 PM

240V ac motor to spin up a flywheel and a clutch to start the genny off it?

hillbillyracer - 4/9/10 at 01:48 PM

quote:
Originally posted by SteveWalker
240V ac motor to spin up a flywheel and a clutch to start the genny off it?

Yeah that's a possibilty, with a shaft direct onto the front of the crankshaft which I could make easy enough.
Most 240v motors are 1400rpm so I'd need a reduction of between 10-1 & 14-1 to get a sensible cranking speed. An old FWD car geabox would do that & it's ready made for the clutch & flywheel if I had a scrap block/engine backplate to mount the motor on.
It'd be a case of engage the gear needed, disengage the clutch, spin the motor up & release the clutch, once started disengage the clutch & put the box back in neutral. It'd mean the gearbox would be spinning in neutral on the output side but what harm would that do?
It'd also really need an over-run clutch on the shaft to the front of the crank so as the engine fired & picked up speed it could'nt drive the gearbox & motor.

So there it is a somewhat Heath-Robinson set-up but do-able on a locost basis. Mabye more trouble than it's worth & it'd be sensible to follow Mango's advice but if we were all "sensible" then there would'nt be a forum about building sportscars from scratch when you can buy a perfectly good & much more practical hatchback from the main dealer!

blue2cv - 4/9/10 at 02:11 PM

blimey its got to be easier to plug a batt charger in

Werner Van Loock - 4/9/10 at 03:05 PM

forget about it, AC motors can't supply the torque a DC motor can from standstill

AC motors can only deliver torque at speed, DC motors have max torque at standstill, that's why starter motors are still DC and not AC as they did with alternators, in the past they used DC generators instead of alternators. (alternator is a AC gen with a rectifier added to it)

RazMan - 4/9/10 at 03:45 PM

quote:
Originally posted by blue2cv
blimey its got to be easier to plug a batt charger in

Are you related to a Mr H.Robinson by any chance??

All this talk about gearboxes, clutches etc - Trickle charge the little blighter - even if the power goes off it will still start because the battery is fully charged!

[Edited on 4-9-10 by RazMan]

MakeEverything - 4/9/10 at 04:44 PM

Bloody hell, you need to occupy your mind a bit more!

hillbillyracer - 4/9/10 at 05:47 PM

Do I get the feeling some of you fellas dont like the idea....

I know AC motors in general aint designed for this which is the reason for the post in the first place! I was looking to see if someone on here knew of a motor that would do it because I did'nt! The clutch & flywheel does get around that problem.
If everybody did everything in the conventional manner the world would be a boring place! I'm just thinking over the possibilities.
& as said I've already thought about & possibly will just trickle charge it but it's not like this thing is all set to go with 12v, key start & a charging system cos it aint, it's got a starter motor & feck all else so all that would be to do too!

Would this be a good time to mention I'm going to use a Ford 2l DOHC carb'd engine & MT75 box?

Ninehigh - 4/9/10 at 11:05 PM

quote:
Originally posted by Werner Van Loock
forget about it, AC motors can't supply the torque a DC motor can from standstill

AC motors can only deliver torque at speed, DC motors have max torque at standstill, that's why starter motors are still DC and not AC as they did with alternators, in the past they used DC generators instead of alternators. (alternator is a AC gen with a rectifier added to it)

You know I was always under the impression that starter motors were DC because the battery was DC

MikeR - 5/9/10 at 12:17 AM

Why not get the mother of all power converters and connect that to the mains with the other end on the DC starter motor.

NB the "mother of all power converters" as i'd hate to think how many amps the starter would draw when you turn on the converter.

Krismc - 5/9/10 at 07:45 AM

Or get a VVVF Drive and run a 240v Ac Motor and you can adjust until correct power for you.

RazMan - 5/9/10 at 07:53 AM

How about a donkey on a treadmill with a connecting shaft? Maximum torque and it runs on carrots!

MikeR - 5/9/10 at 09:24 AM

i think trickle charger is probably the easiest

(what are you going to do with all the poo?)

rusty nuts - 5/9/10 at 12:12 PM

What's wrong with a booster starter/charger? Made for the job

britishtrident - 5/9/10 at 12:38 PM

Boost rapid chargers kill batteries and any charge pumped in won't last long as a rule of thumb for long battery life it takes 5 to 20 times as long to charge as discharge.

rusty nuts - 5/9/10 at 03:57 PM

The original post indicated that he needed to start the engine with what is likely to be a flat battery which doesn't get charged too often . Yes a booster charger/ starter isn't ideal but it would do the job better than anything else given the circumstances

hillbillyracer - 5/9/10 at 08:33 PM

If I use a donkey mabye I could use it to run the lathe etc directly? The poo is no problem, I live on a farm. Then I could sell the genny & use the funds to buy carrots!

I'll likely just go with the obvious & do the trickle charge thing. It's looking the simplest & lowest cost. I'd put the battery in the workshop with the charger & run longer leads (along with the power cable back in & the control/signal wires for it) through the wall to the genny outside.
How do batteries like infrequent use & a constant trickle charge? If the battery would last a few years the it's no big deal. But if the go every 18 months it'd get expensive.
I know repeated boost starting a battery is'nt good, The one I'm using to start it at the moment has suffered with it.

RazMan - 5/9/10 at 10:27 PM

One of the Optimax type chargers will keep the battery in tip top condition for a few years at least.
[url=http://cgi.ebay.co.uk/OPTIMATE-4-MOTORCYCLE-MOTORBIKE-BATTERY-CHARGER-12V-/370351690362?pt=UK_Motorcycle_Parts&hash=item563aae527a]linky[/url ]

02GF74 - 6/9/10 at 10:01 AM

hmmmm.... series 1 land rovers plus other cars from the 50s and 60s had a starter handle - so how much torque can an average human provide?

I know a mains black and decker electric drill has enough torque to get ripped out of my hands when the drill bit got stuck so with suitable gearing down of the motor plus some access to the engine ring gear it may be doable. (<-- yep, that may be a meaningless comparison but ..... )

a starter motor can draw maybe a 100 A, so that is approx 1.2 kW so that is a mains drill drawing 4.5 A. (again, it may be more but not once the engine is turning - a diesel has higher CR so that is not gonna help).

I reckon the numbers are in your favour, not sure how easy or cost effective it would be.

what about a solar battery trickle charger?

[Edited on 6/9/10 by 02GF74]