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StrayAlien
24th Apr 2019, 09:26 PM
Hi all,

Just giving some love to a 1940's Hercus Hacksaw. The motor and its housing are 'of the period' and I would like to keep it if possible. It is 3ph wired for star and no junction box to change over to delta. Of course, I have only 1ph at home. I have some other things running on VFDs so I am familiar but not an expert.

I'd like to explore what my options are for keeping it. I am pretty sure it would be the original motor so in a way, it is important not to separate them. The motor is only 0.5hp - I understand I could probably run it in star config with a VFD but it'll only be 0.25 hp or so which doesn't sound too amazing ....

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The hacksaw doesn't really owe me much and offers some great workshop utility (being larger and more stable than my wobbly- chinesium 6x4) so happy to spend a few bob if professional assistance, or a kind and capable forum member, is required.

All help appreciated.

Greg.

PS. Please, no debates on chinese bandsaws vs old Hercus hacksaws! Just looking to get this old girl healthy again and in 1940's period dress.

Michael G
24th Apr 2019, 09:52 PM
One of the issues explained to me with regards to old motors and VFD's is that because the VFD does not deliver a clean waveform (impossible because of the way they generate the output), there are spikes and old motor varnish may not be able to insulate against these. My suggestion would be to find a motor rewinder and explain what you want to do. They should be able to find the star point, replumb to delta and revarnish. It might cost you a little but at least you will know the job has been done properly.

Michael

BobL
24th Apr 2019, 10:29 PM
Before you modify it I suggest the following .

Test the insulation across any of the Y coil inputs to earth, using a Megger (not just a multimeter) - if it fails its probably a rewind job.
Use a MM to test coils resistance - they should be the same - if not that's a problem
If these are OK try running it on a VFD as is - that will at least tell you if the thing works.

Extracting the common point on these can be real challenging because the insulating varnish is often gooped on in spades and then brittle as toffee.

A hot air gun set on warm and a plastic spatula usually helps pry apart the "gooped coils" so you can find the point. If the varnish starts cracking off the wires when they are moved you are probably on a losing streak.

Periodic checking with the megger as you go can help identify how far back you have to go to find any problem that crops up.

If you are not up for this then a motor rewinder should be able to do it - expect some weird looks when you take it in.

jhovel
25th Apr 2019, 12:01 AM
:exactly: :whs: :wtg:

StrayAlien
25th Apr 2019, 07:05 PM
Thanks Michael, Bob, Joe - and of course a Megger is not a large prehistoric shark .... :-) I did have to look it up.

Okay, I'll do what I can (without a Megger ... ) but I kind of suspected a shop visit would be required. I guess getting a quote is a start.

Bob, the resin is pretty thick (and brittle) on this old girl, I think I could do what you say mechanically, but I have an 'electricity sized hole' in my brain. Somehow, I just can't 'get' electrical stuff. The chances of me frying myself or someone else are quite high.

I've seen vids on running 3ph on single with capacitors etc, but it seems the power output is still quite low - so a no go I guess.

Thanks again,

Greg.

BobL
25th Apr 2019, 08:51 PM
I've seen vids on running 3ph on single with capacitors etc, but it seems the power output is still quite low - so a no go I guess.
Ir will be similar to running the motor as a Y connection.

StrayAlien
26th Apr 2019, 07:32 PM
Thanks Bob - roger that. I figured it might be ....

OxxAndBert
26th Apr 2019, 09:06 PM
Not wanting to encourage you into territory you're not comfortable with, but if you need one you can buy a cheap digital megger on ebay.
They start around $25 delivered, I bought one of the VC60B models for just under $60. Probably does the same job as the cheaper one, but there were some decent reviews on the VC60 so I decided not to go real cheap ;)

Steve

jhovel
27th Apr 2019, 03:08 AM
... and yes, even the cheap ones can give you a good boot! Just like the old school crank handle ones. Don't ask how I know :zap::)(:burnt::damn::doh:

BobL
27th Apr 2019, 09:47 AM
Not wanting to encourage you into territory you're not comfortable with, but if you need one you can buy a cheap digital megger on ebay.
They start around $25 delivered, I bought one of the VC60B models for just under $60. Probably does the same job as the cheaper one, but there were some decent reviews on the VC60 so I decided not to go real cheap ;)
de
Steve

After borrowing the expensive Megger at work many times, back in 2014 I decided to buy a budget level unit and it cost me $76,
I did a review of this on the woodies forum see Budget Insulation resistance tester - product review. (http://www.woodworkforums.com/f271/budget-insulation-resistance-tester-product-review-182461?highlight=Megger)

For less than $1 I bought packets of 1MΩ and 0.1MΩ resistors and made up a test resistor chain so I can quickly and easily check the Megger is working every time I use it. Details of this are posted in the same thread above.

StrayAlien
28th Apr 2019, 08:54 AM
Steve, Joe, Bob - thank you. Looks like I might have to get me one. :-)

A saw a megger operating yesterday actually. A good Samaritan forum member PM'd me about offering help on getting the motor delta'd and was happy to educate a utter nong like me about how to do the conversion.

After a very pleasant afternoon yesterday in a fantastic and inspiring home workshop, some deft hands (not mine!) reconfigured the motor. It is still in bits, so today it'll all (hopefully) go back together and I'll spin it up.

I am very thankful.

Hopefully, I can return that favour to someone here in need ... and keep that big karmic wheel going around.

EDIT: motor runs great. :-)

eskimo
29th Apr 2019, 09:43 AM
I can quickly and easily check the Megger is working every time I use it.

just touch the probes..that tells you if its working...well it tells you roughly how many volts it is sending out:rolleyes:

Ropetangler
29th Apr 2019, 11:00 PM
just touch the probes..that tells you if its working...well it tells you roughly how many volts it is sending out:rolleyes:
Mmmm....... that reminds me of a school friend of mine who shared an interest in radio back in the day. Said friend had a problem with the family pooch, who would periodically chew up components and small circuits built up on molex or tag strips, that is until the day he charged up an electrolytic capacitor to 180V from the B+ line on an old valve radio, and then left it where Fido (a German Shepherd) could easily access it. Fido apparently lost his appetite for electronics after that.:o

Ropetangler
29th Apr 2019, 11:07 PM
Hi all,

Just giving some love to a 1940's Hercus Hacksaw. The motor and its housing are 'of the period' and I would like to keep it if possible. It is 3ph wired for star and no junction box to change over to delta. Of course, I have only 1ph at home. I have some other things running on VFDs so I am familiar but not an expert.

I'd like to explore what my options are for keeping it. I am pretty sure it would be the original motor so in a way, it is important not to separate them. The motor is only 0.5hp - I understand I could probably run it in star config with a VFD but it'll only be 0.25 hp or so which doesn't sound too amazing ....

379138379139379140379141

The hacksaw doesn't really owe me much and offers some great workshop utility (being larger and more stable than my wobbly- chinesium 6x4) so happy to spend a few bob if professional assistance, or a kind and capable forum member, is required.

All help appreciated.

Greg.

PS. Please, no debates on chinese bandsaws vs old Hercus hacksaws! Just looking to get this old girl healthy again and in 1940's period dress.
That could come up really well. I remember a picture of a similar motor style on an antique machine which had been restored by the owner. I think from memory that he had rewired the motor, but the case had been sandblasted, and had plenty of primer filler and much sanding back etc, but the topcoat in Ferrari Red just gleamed like a ferrari too. It looked fabulous!

eskimo
2nd May 2019, 09:44 AM
Mmmm....... that reminds me of a school friend of mine who shared an interest in radio back in the day. Said friend had a problem with the family pooch, who would periodically chew up components and small circuits built up on molex or tag strips, that is until the day he charged up an electrolytic capacitor to 180V from the B+ line on an old valve radio, and then left it where Fido (a German Shepherd) could easily access it. Fido apparently lost his appetite for electronics after that.:o

reminds me of tossing to a mate (a Barrister) a charged up capacitor and telling him to "catch"..lol