Looking for some help....Motor woes

[OldWood]

Roy
I reckoning very few of us could match that - wow.

The hatching bit you won't remember, but as I can remember things at 4, the being buried must have been bloody frightening and quite traumatic. I didn't realise that bombers were still being active as far on as the war as that.

I'm 1+ a bit years behind you - March 1942. Fortunately we were in Devon and far enough away from all the activity. I do have memories from there but unlike my mother nothing related to the war.

So which date are you committing to celebrating the decade?

Rob

 

[Digit]

The machine gunning I knew was true Rob 'cos the bullet holes were still in our front door when the war ended. The bit about the bombing always worried me 'cos according to the official records the town, Dunstable, was never attacked.
Now no one likes think that their mum and dad made things up. When I came out of hospital in 07 I could hardly move and I spent some time looking for a woody forum to join. At the same time I found that the BBC had run a series about people's war time experiences, and low and behold the 'official' line was contradicted in those memoirs.
Several people wrote about the machine gunning and I even found out that the aircraft, a Dornier bomber was shot down shortly afterwards,
but nobody mentions the damn date!
One chap stated that the town was bombed on three occasions by bombers attacking Luton apparently having bombs 'hung up' that then hit us. No dates though!
I don't remember the bombing, I came round to find mum and dad frantically digging me out of a pile of rubble then dad carrying me across the road to the doctors. I was bleeding all over the place from a scalp wound and the doc sat me on the floor between his knees as my head was shaved, and to this day I can recall his needle scraping my skull as he stitched me up.
I was a hero at school till the bandages came off! :lol:

Roy.

 

[GraemeD]

Sorry to drag you all back on topic.....those of us who were children of the sixties seem to have missed out on some fun!

Just wondered what the recommended current rating for the start cap switch would be? I know the static current is not so high in a 1HP motor, but we're talking starting currents here, and I don't want to have my contacts welded!

I'm still mulling over solutions, but currently looking at DIN rail mounting mains timer/relays, which seem to be available at good prices (£10-ish) on Ebay. I'm thinking that these are designed for the task in hand, and would be a drop-in solution. Just that the one I'm looking at has 10A rated contacts, yet also says it is good for single phase motors up to 0.55kW, which lead me to believe the starting currents could be huge!

Any thoughts very welcome!

Graeme

PS. My first elec project was based on OC71s too....the Ladybird book of Electronics, making a radio!

 

[9fingers]

10 amps 'feels' a bit light but I've not got any firm information to support this.

I've never had a 1hp motor trigger a 30amp type B (normal domestic) MCB which are quite fast acting but I have sometimes had my 1.5hp jointer blow a traditionally slow 13amp plug top fuse in cold weather. Which might be a bit nearer the sort of mechanical starting load of your planer although mine is a modern Jet with less spinning cast iron than yours and only 200mm wide

Depending on what bits and pieces you have lying around, I would suggest that you use the timer relay to drive the coil in a contactor in a re-wired NVR dedicated to starting. This would give you contacts designed for high inrush and big open gaps for the sparks on disconnecting. A further benefit would be the overload trip that might just help protect your start windings.


As part of trying to answer your question I looked at the only 1hp single phase machine I have, a morticer only to find the switch in that to be rated at 6 amps :shock: That has minimal inertia at start up I suppose but
typical chaiwanese 'just not quite enough' engineering.
I'm now unhappy about that!!

Bob

 

[Digit]

Yes Graeme, you did miss out on some fun, for kids it was a fantastic time, but back to the subject. In theory 10 Amp should do it, but bigger would be better for longevity.
Remember, no current flows till the contacts are made, so the smaller the contacts the greater the heating effect, but a lot of damage can also occur as the switch breaks, this is when the arcing takes place that erodes the contacts.

Roy.

 

[OldWood]

Graeme - my apologies for the wandering away from the topic ! I suspect I was the instigator

Bob - would looking at the starter switch for a bandsaw be worth considering for an indication of 'capacity' as they have a fair inertia to wind up. Mine's got a 1hp motor (6A 0n the plate) and the NVR looks pretty bog standard.

Rob.

 

[OldWood]

Remember, no current flows till the contacts are made, so the smaller the contacts the greater the heating effect, but a lot of damage can also occur as the switch breaks, this is when the arcing takes place that erodes the contacts.

Roy.

Ahh, yes of course it's an inductive load so the current lags the voltage.

Rob

 

[GraemeD]

Rob....no need to apologise....the background conversation made me smile! And it keeps the thread alive when I'm otherwise distracted.....

My fear was that when the contacts close, they are connecting a pretty low impedance load with a large inrush, and since they are mechanical they don't do this instantly....leading to heating as you say. By the time the switch disconnects, I presume the current is much reduced, as the motor is up to speed, but still is not insignificant.

I was thinking relays, but Bob mentioned contactors.....I'd not thought of that approach (remember I'm a low power kind of chap!). I don't have such things lying around, but a quick look on Ebay shows you can pick up DIN rail contactors rated at lots of amps for only a couple of quid. I'm seeing a plan form here.....a small DIN rail box plus a DIN rail timer and a contactor alongside, all wired through my DOL starter (for overload protection). I think these DIN rail devices are widely used in industry and hence come up onEbay as surplus, and at good prices. Liking a bargain, I'm thinking this may do the trick.

Graeme

 

[Digit]

That is the route I would take Graeme. No soldering, robust, easily adjustable and repairable if necessary.

Roy.

 

[Digit]

For those who have been following the deviations down memory lane, I've found it!

It was Thursday September 12th and Mother was walking up the high street, heavily pregnant with my sister. She met a friend outside what is now the little theatre and was having a bit of a rest when an aircraft came down the road - bang, bang, bang! There was so much tree cover she was lucky. When she went into labour that night, she was certain that’s what brought it on.

So now I know that mum was right, I was born on the 12th.
The story I got was that dad, on 12hr shifts + fire watching, didn't get around to registering my birth within the legal time, so added a few day to the actual date to keep out of trouble!

Roy.

 

[OldWood]

For those who have been following the deviations down memory lane, I've found it!

It was Thursday September 12th and Mother was walking up the high street, heavily pregnant with my sister. .

Roy.

Badly written, Roy, or is the logic incorrect here somehow ? Ooops I'm high jacking Graeme's thread again.

Rob

 

[Digit]

I'm not with you Rob, it's from here...

http://www.bbc.co.uk/ww2peopleswar/stor ... 5793.shtml

Roy.

 

[OldWood]

I think it should read "....my mother, heavily pregnant, was walking up the road with my sister...." --it reads as if it was your sister she was pregnant with.

Rob

 

[big soft moose]

well if we're going to be picky about grammar

When I proposed to my wife Rob I told that whatever the future might hold it would never be dull!
.

your wife was called rob ? - thats an unusual name for a girl :lol:

 

[Digit]

I surrender! :lol:

Roy.

 

[GraemeD]

Blimey....I started a thread about motor problems, and ended up proving one of the forum members disputed birthday!! How did that happen!!??

Great thread.....I'm certainly happy that we've worked out what to do with my motor; the rest was great entertainment.

Isn't the internet wonderful!

 

[Digit]

Blimey....I started a thread about motor problems, and ended up proving one of the forum members disputed birthday!! How did that happen!!??

A perfectly logical progression! :lol:

Roy.

 

[OldWood]

Graeme - we also worked out that his wife is called Rob. I worked once with a Mr Hood whose wife was Robin

And BSM it's not actually a grammer problem (pedant hat on!!) - it's a bit like that book title "Eats shoots and leaves". Spoken, the emphasis and the spacing gives the meaning; written the actual meaning is in doubt, and is therefore bad writing.

Sorry Graeme - it's all irrelevent really. I like your solution with the DIN rail. I hadn't thought of that solution when I suggested the delay relays from Farnel.

Rob

 

[Digit]

Just to confuse you further my wife is named Jo! :lol:

Roy.

 

[9fingers]

I'm a tad disappointed that my modified toaster timer has fallen by the wayside. I'll have to try it myself next time I get a motor with a nackered switch.

Bob :x :lol: :roll: