Hello from Oban

Hi, after many years thinking about it I am going to make the plunge into model engineering. I’ve done a bit of lathe work, but will need help. I am going to join the nearest club, but they don’t have a website so will need some searching out.

My first question is this... I rent a property, so can’t do major changes. However, I do have a big shed - 16x8. This isn’t on mains, but does have 12V from solar panels and batteries. I know I can buy a 1000W inverter, but is it feasible to drive a lathe from such a system. I can sort out battery capacity myself - electrical engineer in previous life. The other option is using my school’s lathes - now a teacher. Better to model at home and be able to play whenever I want.

Smaller lathes would be more feasible, but what makes sense? Am I being too hopeful?

Thanks

Dave

Unless you can get some ex fork lift batteries and a big enough PV array to serve them you will be limited to a few minutes at a time. A treadle lathe will do a lot of things though if you have the back up of a lathe at work for the bigger stuff. You could look at a small well silenced IC engine and lineshafts as was done 50 years ago before small electric motors became commonplace.

I suspect that modern electric motors are more efficient, but: Atco used a nice 1/4 hp motor in one of their lawnmowers, powered by a 12V battery. ... This would drive a small-ish size lathe quite adequately.

MichaelG.

.

Edit: Just found this reference:

https://www.oldlawnmowerclub.co.uk/mowers/moms/mp036-atco-battery-mower-1950s60s

Edited By Michael Gilligan on 02/03/2018 18:49:19

Entirely dependent on shed placement but possibly just a long extension able from house to shed?

Sadly, shed is 150 feet from the house.

Dave

Which is far enough that a quiet generator wouldn't disturb the family.

Anyway, the workshop in my previous house (still mine, but not sold yet) was also about 150' from the meter in the house cellar. I just ran a cable down the garden, off some planted scaff poles, and it's still in use 25 years later. I always intended to wire it in via a proper dedicated breaker, but it's been running off a 13 amp plug all these years, without even blowing a fuse.

I've run MIG & arc welders, lathe, 2 mills, 2 pillar drills, T&C grinder, linisher polishing spindles, fan heater etc. just not all at the same time.

Bill

Edited By peak4 on 03/03/2018 01:57:46

Quiet generator might be the way to, but idyllic here. Don’t want to scare the otters, seals or red deer!

Dave

The best solution is to have the workshop in the house. If that isn't an option, just get a long cable, and start making something. Presumably that is the object of the exercise.

only 150ft - no problem. a generator is 5 times the price and a general nuisance. If you lay in a proper armoured cable it will enhance the value of the house long term.

For comfort, convenience and all-year-round use, you could do worse than consider what has been described as a 'Home Lathe', e.g. Cowells, Unimat 3 (early models ), Peatol, Sherline etc. OK, so you won't be able to make ride-on traction engines or steam choo-choos but for some, the satisfaction is in making 'something' . John Wilding made a very nice clock on a Unimat , for instance - just a thought.

rgds

Bill

Should be able to run a 12v motor from battery, hobby use you won't be running long periods. I have a couple of 1/2 hp batteries from a scooter and they run about an hour of an old car battery. Sunny Oban, you might be better with a small wind genny?

David's question calls for sums!

You need to estimate the power consumption of the shed (at least the lathe, plus lighting and any other equipment), and compare it with what could realistically be produced and stored by solar panels.

The power consumption (in Watt Hours) of the lathe depends on the motor size and how much it's used.

• My 1.5kW lathe doesn't add noticeably to my electricity bill because even on a busy hobby day it's only used in short bursts. I reckon I'm a light user; I'm unlikely to spend more than 6 hours a day in my workshop of which the lathe is only on for, say, 10 minutes per hour. About 1.5kWh per session, probably much less because most of the time the lathe isn't actually cutting, and some days I don't use it at all. I think my lightweight pattern of consumption could easily be satisfied with a solar panel/inverter/battery combination.
• The same 1.5kW lathe in other circumstances would be much more problematic. On a 1940's production line lathes were run at an 80% duty cycle throughout a 3-shift system until they wore out. A lathe not cutting metal was wasting money and they were kept busy. Such a machine would burn about 30kWh per day, ouch!

A 100W 1m x 0.7m solar panel kit as sold for boats and caravans costs about £150 and produces about 500Wh per day. Three of them coupled to a suitable battery would satisfy my needs. Actually, a single panel producing 3.5kWh per week would run a 1.5kW lathe flat out for about 2½ hours. That might be good enough.

It's not quite that optimistic.

• David lives in Oban and we don't know if his shed roof faces what sun there is. He might need another panel or two to compensate for lack of sun and a poorly aligned roof.
• Solar panels don't make electricity on demand. Not good in mid-winter on a flat battery if you have an urgent need to do a few hours heavy cutting.
• You need a big battery suitable for this type of charge/discharge.  Not an old car battery!

The shed being rented I'd be inclined to run a temporary cable to the shed and only plug it in when wanted. Something more solid than a domestic drum like a builder's site extension cable. Obviously the practicality of this depends on location. A temporary cable down the side of a private garden is not the same as running the same wire along a public footpath.

Dave

Edited By SillyOldDuffer on 03/03/2018 10:47:09

With due respect to David, he was an electrical engineer and is now a teacher. I am surprised that he needs to ask the question.

With a good battery bank, a charging system of solar cells and a wind turbine would be the way I would go. Batteries ex electric fork lift trucks are some times available, and (I think) there is a price payable by those wanting to dispose of them, so you might get them for the cost of collecting, you could shout them a slab of beer, or something like that.

Ian S C

Dave, (The OP Dave that is) as per my earlier post, which was far too late at night, something I forgot to mention.

If it is practical to run an armoured cable down/up to the shed, consider running a CAT5e/CAT6 cable and a phone cable at the same time.

(2.5mm armoured will probably suffice, but 4mm isn't that much dearer. but I'm sure you can investigate that yourself knowing your previous occupation)

The network cable may be handy for looking up stuff on the web whilst working down these without trudging back to the house in inclement weather.

The reason I mention a hard wired phone, duplicating the one in your house, is that 150' is a fair way for shouts for help to be heard in the unfortunate circumstances of something going pear shaped in the workshop.

Bill

.

By my reading; David's actual question was:

I know I can buy a 1000W inverter, but is it feasible to drive a lathe from such a system.

... and the short answer to that must be YES.

... a longer answer would require a definition of what David considers to be 'a lathe'

MichaelG.

Dave, your wildlife will soon adapt to the noise from a generator, they are intelligent and when they no longer see it as a threat they will just ignore it and carry on with life.

Dave W

It should be obvious to anybody with half a brain that the simplest, quickest and most cost-effective method of getting power to the shed is to lay a cable from the house - either temporary or permanent.

I think David knows that already.

Thanks for all the comments. If I owned the house I would have power down to the shed already. Problem with renting is that I don’t want to spend money on armoured cable etc. I could be out of here in 2 months if the landlord so desires... I also don’t want a cable as it might cause issues with the estate agent...

Yes, I know how to do the calcs, for power (pretty basic really) but the question is the duty cycle that has been mentioned already, thanks very useful. 10 mins per hour makes it feasible. Solar panel is S facing, so gets as much power as possible. Lighting is LED strips and is very efficient.

What I really need to know now is if a 1000W max lathe is man enough to do the job I want - build a 5” gauge loco. Also how much of the time cutting are you running at this max power? If most of the time it will be running at less then it gets even more feasible.

Thanks Dave

Dave, I did wonder if that was the case with the armoured cable.

One thing I wonder about, running a motor off an inverter, isn't that 1Kw is enough to run the lathe, but whether it's enough to handle the surge current when the motor starts up.

My Myford has a 570w motor, but if started conventionally, would probably trip out a 1Kw inverter.

I wonder about the possibility of a 240v soft starter, or using an inverter to power a single to 3 phase VFD, as either of these should help smooth out the start surge.
What I don't know, is how either device would run off an inverter; I guess you would need to consult the manufacturers of both the devices you proposed to use.

Incidentally, as I'm sure you are probably aware, the same issue might arise with a generator if it didn't have enough current headroom. My little 600w Honda suitcase won't drive a 450w angle grinder as the start-up surge trips the genny. It's perfectly happy with a 600w variable speed electric drill, even when drilling maximum sized holes, as effectively, the drill has its own built in soft start.

Bill