OXFORD RT 250 - No leads

[Jaeger_S2k]

Evening

Picked it up today have checked the Capacitance across N and 240 1 ohm.

Anything else I can check?

The High Low selector is stuck (on High, it came off a farm), how do I clear that?

The power selector is stiff, how do I loosen that up a bit?

2 or 3 can't remember of the tops holding bolts are sheared (the ones under the handle, I can understand them going with heavy hands - see Farm note above). Will drill them out and tap once I know she's good.

The wheels are round and do turn, that's a good sign isn't it?

Oh all these questions but I'm still smiling

Yes they are heavy and getting it off the van myself was interesting!

It didn't come with leads, anyone got some I can borrow to check her out?
I need to grab a 16amp supply so nothing too urgent as I got to fit the new consumer unit after pulling the BIG fuse.

 

[JayRS4]

Omniata may have a spare set of leads, he was talking about replacing the ones on the oxford he bought from me, but there`s nothing wrong with them

 

[Jake SS]

Would check the "resistance" again, or better still use a insulation tester/ megger.
Wires and to frame to make sure it is safe to plug in first

You would have to strip it down to get at switches
Try some penetene on knobs to get them off
I have used electrical grade gunk remover to free up switches etc.
Must clean off properly after doing so
Be careful not to force gunk inside of parts !

Cheers
Jake

 

[zzr1200]

Looks good, but one small problem with you plan, your going to have to have a 32amp plug minimum and 6 or 10 mm cabling from the fuse board for that baby.

The control knobs are held in place by grub screws, remove the nuts from the input/output terminals and then pull the lid to gain access to the transformer selectors.

Remember that transformer oil is nasty (carcinogenic) stuff, before you drain the oil find out how much the replacement oil is....

PS: how many beer tokens for the welder???

 

[Jaeger_S2k]

Omniata may have a spare set of leads, he was talking about replacing the ones on the oxford he bought from me, but there`s nothing wrong with them

Oh. I may just ask him how he's getting on. I have to check with my mechanic he may have a set 'just lying around' never know.

Would check the "resistance" again, or better still use a insulation tester/ megger.
Wires and to frame to make sure it is safe to plug in first
You would have to strip it down to get at switches
Try some penetene on knobs to get them off
I have used electrical grade gunk remover to free up switches etc.
Must clean off properly after doing so
Be careful not to force gunk inside of parts !
Cheers
Jake

Yeah Jake, more tests needed.
That's just it, I don't want to plug it in before I have a good idea it's safe. I'm quite confident it's not going to cause a problem but better safe .....
Have had all the switches and knobs off and bolts and the lid lifts off (just from each side, didn't have a lift set up ) so plan is to do just that. Lift the lid on a rope tied to the roof and work from there. Good strip down and a clean and rebuild. It's all part of the enjoyment for me getting it looking like it was when it was young.
What's penetene?

Looks good, but one small problem with you plan, your going to have to have a 32amp plug minimum and 6 or 10 mm cabling from the fuse board for that baby.

The control knobs are held in place by grub screws, remove the nuts from the input/output terminals and then pull the lid to gain access to the transformer selectors.

Remember that transformer oil is nasty (carcinogenic) stuff, before you drain the oil find out how much the replacement oil is....

PS: how many beer tokens for the welder???

6mm should be fine. It's sited in air and less than 10mt from CU. 43amps all day long.
BIG plug though
Need to check it's worth further work (like it'll not boil) have read about the nasty oil but your point is noted and welcomed. 57 litres of oil, if I was to drain it it would be into a safe reciprocal strained and put back in.

If I can confirm everything electrically is good. How would you guys suggest refurbing it?
I'd like to 'give it a service' clean the controls so they operate better etc. I was thinking lifting the top out enough for the components to clear the oil and leave to drain. Not sure they would be happy to hang in air without the support of the oil?
I'll disclose how many bear tokens once I know she's good to go. But was more than Zardoz paid for his, not a lot more though

 

[Weldingartisan]

A couple of timber battens to hand, unbolt the lid lift up while someone slips the battens across the case and rest the carcass on top for the oil to drain in the tank. Then you can inspect/repair at your leisure. W/A

 

[Robotstar5]

I've used a decent set of jump leads to test a stick welder - cheapo aluminium ones melt!

 

[GeorgeB]

That's just it, I don't want to plug it in before I have a good idea it's safe. I'm quite confident it's not going to cause a problem but better safe...57 litres of oil, if I was to drain it it would be into a safe reciprocal strained and put back in. If I can confirm everything electrically is good. How would you guys suggest refurbing it?

You're being a lot more cautious than I'd be! I'd just plug it straight into a normal 13 amp socket and see if it either blows the fuse or produces 50/80 volts when a simple multimeter is put across the output terminals. If it produces the expected voltage, I'd set it on the minimum current (20 or 30 amps perhaps) and try a weld. There's no way it will blow a 13amp 240V fuse on the lowest output setting, unless it's faulty.

Other than taking a quick look at the switches and contacts, what tests can you do, other than with electrical safety test equipment?

If the oil smells 'distinctive' it's probably the correct, special, transformer oil. But many of these old units will have had the special oil replaced with car engine oil decades ago. If it doesn't smell of much, it's probably car engine oil. Either way, that oil could be laden with water/mositure and is probably best discarded. I'd sooner use new engine oil than old 'special' oil, even if it's been strained. Straining won't remove the moisture.

I recently tested the conductivity/insulation of car engine oil by passing 5000 volts through it. There was no more conductivity than if you were trying to pass 5000 volts through a 1 metre thick block of rubber.

 

[zardoz]

Im glad you got a bargain, though you could have had mine for the asking, along with 25 foot of leads. Been trying to get rid for a while. Just taking up space.
ps: if you think yours is heavy then let me tell you that 3 of us couldnt lift mine!

 

[mishka]

Hi,

Remember that transformer oil is nasty (carcinogenic) stuff, before you drain the oil find out how much the replacement oil is....

The original Shell Diala B is not carcinogenic.

Cheers.

 

[Archie]

All oil is carcinogenic apparently. IMO, talk of taking great care when changing oil is a bit OTT. Point taken if you're doing it on a regular basis but someone doing a one-off oil change is hardly going to erupt in cancerous tumours are they. You'd probably be at greater risk eating food from the BBQ.

 

[Omniata]

Used engine oil can be nasty. Old transfromer oil contains PCB's which can oxidise to dioxin, that's nasty too...

Most modern transformer oil is safe, and cheap, though by world standard and designed for the purpose...

 

[zzr1200]

Hi,



The original Shell Diala B is not carcinogenic.

Cheers.

I was lead to believe this was the case, I appear to have been mis-informed...

 

[Omniata]

Main hazards from the MSDS for the Shell oil would only be a problem if you were to drink it...

 

[Jaeger_S2k]

Main hazards from the MSDS for the Shell oil would only be a problem if you were to drink it...

No I won't be drinking it.

 

[Jaeger_S2k]

You're being a lot more cautious than I'd be! I'd just plug it straight into a normal 13 amp socket and see if it either blows the fuse or produces 50/80 volts when a simple multimeter is put across the output terminals. If it produces the expected voltage, I'd set it on the minimum current (20 or 30 amps perhaps) and try a weld. There's no way it will blow a 13amp 240V fuse on the lowest output setting, unless it's faulty.

Other than taking a quick look at the switches and contacts, what tests can you do, other than with electrical safety test equipment?

If the oil smells 'distinctive' it's probably the correct, special, transformer oil. But many of these old units will have had the special oil replaced with car engine oil decades ago. If it doesn't smell of much, it's probably car engine oil. Either way, that oil could be laden with water/mositure and is probably best discarded. I'd sooner use new engine oil than old 'special' oil, even if it's been strained. Straining won't remove the moisture.

I recently tested the conductivity/insulation of car engine oil by passing 5000 volts through it. There was no more conductivity than if you were trying to pass 5000 volts through a 1 metre thick block of rubber.

Was that 5/40 or 10/50?
I can't believe your suggesting engine oil when you say the smelly stuff will be 'Special'.
That's a bit like saying I should just use standard 15/40 oil in the Honda?

I will not be following your recommend on this one George but I can imagine the boys at Oxford are kicking themselves for all that wasted effort in putting in 'Special' oil? But thanks for the post.

If you do come across moisture laden oil, insert a fish tank air pump and let it aerate the oil for a could of days, the moisture will have the opportunity to bead and fall to the bottom. Suitable tank is useful for this, funnel shaped base with a drain off. It's a common problem overcome when making Bio-Diesel.

A couple of timber battens to hand, unbolt the lid lift up while someone slips the battens across the case and rest the carcass on top for the oil to drain in the tank. Then you can inspect/repair at your leisure. W/A

Nice one Weldy, just how high does the top need to come out to clear the oil? I was thinking it would be quite a lift hence the idea of stringing it up.

I've used a decent set of jump leads to test a stick welder - cheapo aluminium ones melt!

Got a good set in the van BUT the good news is my mates got an Oxford in his garage, the things you learn. Should be able to borrow a set of leads for testing.

Now where's MK with a list of tests I need to do?

 

[GeorgeB]

Was that 5/40 or 10/50?
I can't believe your suggesting engine oil when you say the smelly stuff will be 'Special'. That's a bit like saying I should just use standard 15/40 oil in the Honda? I will not be following your recommend on this one George but I can imagine the boys at Oxford are kicking themselves for all that wasted effort in putting in 'Special' oil? But thanks for the post.

I only used the term 'special' because I couldn't recall the proper name - Shell Diala B or whatever. I'm sure that for crucial applications, it may offer some advantages over bog standard car engine oil - 5/40, 10/50 or anything - it's all designed to transfer heat out of a car engine. So, car engine oil should work for transferring heat out of a transformer, too. That's why so many people have used it in Oxford welders over the years. The other main factor is whether car engine oil is an insulating oil. I say it is because I couldn't get it to conduct electricity when I tried a flash test. What other factors could there be?

If Shell Diala B is available locally at close to the price of car engine oil - sure - use it. But by the time you've paid for carriage, and the higher price of the Shell Diala B oil in the first place, my guess is that it will end up a lot more expensive.

 

[malcolm]

Note that engine oil contains a lot of additives, sulphur content isn't as well controlled as in transformer oil, and manufacturers may not have had the foresight to make sure all the coatings on the transformer are resistant to engine oil (in a car engine rubber parts are a special material).

Engine oil does tend to attract water too, which makes it poor for rust proofing. You think that might make it conductive?

If you think all oils do the same thing, but don't have an Oxford to test, why not try a bit of vegetable oil in your car? It's cheaper than engine oil. But it would be a shame to ruin a nice Oxford for the sake of saving a few quid.

 

[mishka]

Here is the spec sheet for Shell Diala B:

http://ptskm.com/GTDS_Diala_B.pdf

for those interested in fact rather than fiction.

 

[Jaeger_S2k]

I'm puzzled?
All Oil isn't equal.
Gearbox oil - Why?
Engine Oil - 0/30 through various variations and flavours - Why?
Differential Oil - Why?
Transformer oil - Why?
I'm sold on the idea that there is a specific oil that should be used for a specific function. Main reason is I run a high revving 9000 RPM engine on full synthetic 5/40 engine oil.
I also use specific gearbox oil and specific differential Torsen Limited-Slip Differential.

So if I replace the Oxfords oil it will be no surprise to find it will be Transformer Oil designed for the purpose of cooling a transformer by oil.

I don't care if you think it will work, if you are so convinced do it to your own Oxford but don't recommend it to others.