Running DC starter motors from welding plant.

[evildrome]

So, I've got a couple of Rolls Royce 24V starter motors from... something military.

They are very nice indeed and run very quiet.

But they take 24V and 200- 300 Amps when doing useful stuff.

I'd like to incorporate them into maybe a small home made milling machine or planer table or something.

What's put me off is finding a suitable power supply. I've thought of rewinding a MOT but... it's a bit Heath Robinson for something that's going to get regular use.

Then I saw this miniGB ZX7-200 220V 200A Mini Electric Welding Machine IGBT DC Inverter ARC MMA Stick Welder 220V

and I'm thinking... 20 - 28V at 200A ? Sounds interesting. I'm only looking for intermittent loads, maybe 5- 10 mins at a time.

But there's all that resistive / inductive load bollocks. Its like cross-ply and radials. If you get it wrong kittens will cry.

So in order to prevent crying kittens, can someone tell me if you can run DC motors from welding plant?

(BTW I've also looked at old oil tank MMA welding plant that you can buy for £5 but they're heavy AF, they smell, they sometimes leak, the voltage is wrong (7v?) & the same query applies to those too).

 

[flh801978]

Bear in mind to get 300 amps at 24v from a 240 supply you need a 30 amp + supply

Be far better off to use a single or 3 phase induction motor to drive what you want at 10-13amps will give you 3hp

 

[Jelly]

As an FYI, it's pretty likely that your starter motors are unlikely to be rated for a continuous duty cycle, and would burn out if run continuously for any length of time.

Further to that, those tiny welders have a reputation for overstating the current capacity they offer substantially on the listings (I think This Old Tony showed one on his youtube channel which performed at about ½ the power it claimed), in principle that one should draw 7.2KW to provide 300A at 24V, which is not happening through a 13 A plug!

Nor is it very likely that welder will be able to operate on a continuous duty cycle (unless it doesn't have a thermal cut-out, in which case it will be able to but shouldn't as it will eventually melt/catch fire).



Those concerns aside if you really want to have a crack at this:

I helped a friend build an induction furnace once (worked reasonably well, but was a distinctly sketchy apparatus during the development process, until he finalised on the design and provided an enclosure); which required a large DC supply for the circuits.

He had a great deal of success with running 4 * 1000w 24v PSU's like these wired up in parallel to deliver a 24V dc supply with sufficient current capacity for the induction circuits, you can get them substantially cheaper than the amazon ones I linked (I think my mate got them for about £18 a piece), and that might be a better alternative to the welding supply.

 

[Spectric]

Starter motors have the field and armature windings in series so that it can produce maximum torque, designed for very low duty cycles just like any starter motor and if run continous will go up in smoke.

 

[AES]

Just FYI, it is I think, unlikely that your R-R starter motors are ex-military aircraft (though a big tank or motor torpedo boat is possible I guess).

More likely they are from the R-R Dart turboprop (which was mainly for civil aero applications), though some, much fewer, were flown by the military.

If ex-R-R Dart, then I can tell you that they're "only" rated to run for 1.5 minutes max, AND in the event the engine had not started after (if I remember correctly, 3) separate attempts, then you had a mandatory cooling down period of (again IF I remember) 5 mins, minimum. Remember that in that application (rather old-fashioned by today's standards) that motor has got to turn both the engine compressor and turbine, PLUS the gearbox, AND also the propeller! In other words, quite a big load, hence the above duty cycle limitations.

AND, BTW, the aircraft below were all twin-engined, and soon as you got a start from the first engine standard practice was switch over to the aircraft's own (engine-driven) geny to power the engine No. 2 start.

Also FYI, the ground-based power for starting such aeroplanes (think Fokker Friendship, HP Herald, Avro 748, Vickers Viscount, etc) came either from a big petrol-engined generator cart, or, if nothing else, from a "trolley acc" - a large 2 wheeled trolley (just about 1-man-pushable, but usually tractor towed) "filled" with loads and loads of LARGE lead-acid batteries all inter-connected with gurt big straps.

I don't have enough info to know where else to look for suitable power (unless you want to buy an ex-MOD trolley acc!) but frankly, nice though they may be, I suggest you should find something much more suitable for your mill project.

Sorry to rain on your parade.

 

[kenledger]

I would have thought they be worth quite bit to right person and then you could buy you self a planer.
They are rare parts now and restorers are alway looking for parts.

 

[AES]

You may be right kenledger. But first off, those motors need properly identifying (Part No & Serial number) to know EXACTLY what they are/what the fit. And secondly, IF my pure guesswork was correct (above) and they ARE from R-R Dart engines, then AFAIK, there aren't too many people rescuing Dart-powered aeroplanes these days, and even fewer people still actually operating them.

I'd class that idea as worthy of consideration but most likely a "definite maybe"! As above, first off, we need to know EXACTLY what they are.

 

[Jelly]

I would have thought they be worth quite bit to right person and then you could buy you self a planer.
They are rare parts now and restorers are alway looking for parts.

This is a good point, there are a lot of RR engines kicking about in preservation too, so it's just a case of finding the right place to advertise them.

Edit:

You may be right kenledger. But first off, those motors need properly identifying (Part No & Serial number) to know EXACTLY what they are/what the fit. And secondly, IF my pure guesswork was correct (above) and they ARE from R-R Dart engines, then AFAIK, there aren't too many people rescuing Dart-powered aeroplanes these days, and even fewer people still actually operating them.

I'd class that idea as worthy of consideration but most likely a "definite maybe"! As above, first off, we need to know EXACTLY what they are.

By contrast, if they're off the much more numerous Diesel engines RR built in Shrewsbury, then there's dozens of easily identifiable potential buyers in the heritage rail sector.

It makes fully ID'ing them the critical step in reselling them.

 

[AES]

This is a good point, there are a lot of RR engines kicking about in preservation too, so it's just a case of finding the right place to advertise them.

As above, "maybe" Jelly. But if I may (at least slightly tongue in cheek) correct you, if you have any dealings at all with Rolls-Royce people themselves (at any level) they are most likely to have a major hissy fit if you leave the hyphen out - even with just the initials - it's ALWAYS "R-R"! (Don't know if that applies to the car people as well as aero though, I never swam in such rarefied car waters)!

But seriously, the first step is for the OP to get P/Nos & S/Nos. Then (IF we can find out) we'll know where to advertise them. IF they really ARE off Darts, then I MAY even have a contact (there are still some Avro 748s -"Budgies" - in service I think).

 

[Jelly]

As above, "maybe" Jelly. But if I may (at least slightly tongue in cheek) if you have any dealings at all with Rolls-Royce people themselves (at any level) they are most likely to have a major hissy fit if you leave the hyphen out - even with just the initials - it's ALWAYS "R-R"! (Don't know if that applies to the car people as well as aero though, I never swam in such rarefied waters)!

The only part of Rolls-Royce I've ever dealt with refers to themselves purely as "Submarines", no R-R (and no starter motor necessary, come to it...).

 

[AES]

"What's a submarine"? please Jelly

 

[Jelly]

"What's a submarine"? please Jelly

Slow, wet aeroplanes with stubby wings and a solid steel canopy for the pilots to not see out of.

 

[TFrench]

Could be from a B-series engine as well - we have an Austin Champ which has a RR designed engine. Runs on 24v and the starter motor is an absolute monster for a 4 cylinder! The B-series was modular - little things like the champ got the 4 pot, medium vehicles got the 6 and big things like the stalwart got the 8.