Thread: Bueller's shed - a noobs journey through vintage machinery

^ Yep that's the plan. I'm actually going to go with the idea to attach the grille to a piece of steel shroud which I'll knock up with a few different sized openings. Then I can fine tune just how much vacuum I want by swapping them out.

Originally Posted by bueller

^ Yep that's the plan. I'm actually going to go with the idea to attach the grille to a piece of steel shroud which I'll knock up with a few different sized openings. Then I can fine tune just how much vacuum I want by swapping them out.

Another possibility is to use a loose piece of sheet metal hung across the opening from a couple of pieces of wire and adjust the size of the opening accordingly. Save a lot of welding.

I'm thinking I'll probably knock it all together with the grill just wedged in and then see how the flow is once it's up and running. Then I can figure out the sweet spot and knock together the removable grill and shroud.

Originally Posted by desbromilow

Great work, I've only jumped on this thread last night....

I've noticed that in at least 2 of your photos you have your angle grinder plugged into a partially uncoilied lead - the rest of the lead is still coilied by at least 7 turns on the holder.
I would encourage you to fully uncoil your lead when using power tools to avoid any voltage drops caused by the choke effect of coiliing your leads, plus you're reducing the heat disappation of the lead as well.
People can go years without issues, but the instructions for your tools tell you to fully uncoil for a reason.

Keep up the good work,
Des (near Pinjarra)

Missed this initially, thanks Des!

Made a mental note about the extension lead, won't do that in future.

That technique of coiling the power lead is how boiler makers some times reduce the current on their welders when working at a considerable distance from the power source.

Regards
Paul

While I agree its a good practice to unroll extension cords before use, one also needs to be mindful of the situation they are being used in.

Today I measured the voltage and current at the end of a 30m 10A extension cord driving a 5" angle grinder.

Direct from the GPO the voltage was 241V while the angle grinder drew 2.2A while free running.
Putting the grinder under load the current went up to 3.5A and the voltage dropped to 240V

With the grinder attached to the extension cord rolled up the V at the end of the cord was 238V with the angle grinder free running and 237V/3.5A with the grinder under load
With the extension cord unrolled the V was 239 with the angle grinder free running and 238V/3.5A with the grinder under load.
The choking effect of the 30m coil is 1V in this situation - I repeated this test several times and even though the mains at the GPO drifted up and down a few volts the voltage differences were pretty consistent.

Using the Volts and current data for the cable under load
The energy loss in the cable for the grinder connected to GPO is Vdrop X I = 1 V x 3.5A = 3.5W
The energy loss in the cable for the cord rolled up is Vdrop X I = 4 x 3.5 = 14W
The energy loss in the cable for the cord unrolled is Vdrop X I = 3 x 3.5 = 10.5W

The cable when rolled up is very tightly rolled onto a 100 mm diameter drum.

The data is all +/- 1V and 0.1A so its not very precise and my science hat says there's nothing in it but taking the data as is, in this situation the rolled cable is only just noticeably different from the unrolled cable. In fact in terms of W/m of cable , if anything the short cable direct from the socket is under a greater thermal load than the extension cable in either situation.

Now there is still 14W of power being generated in the rolled up cord when under load compared which means the wire will get warm but how warm ?
For example, during the testing with the coil rolled up I could not feel any changes in the coil temperature although I will admit I did not let it run for more than a couple of minutes..
The IR thermometer indicated a 2º change in temperature but that could have been due to me constantly touching the cord

I have done this experiment before, but to see a definite change in temperature I had to use something that draws more current, i.e. a old transformer welder
See Can I run 2 hp motor off an extension cord

With a welder the temperature of the coiled up cord went from 19º to 30º just having the welder plugged in but not running a bead it was drawing around 7A and then welding 4 rods took it up to 45º.
This is about what I would expect because of course the welder drops more V and draws more current so the total watts developed in the cord will be greater.

The other factors that should be considered is the rating of the cord, the state of the cord itself, how much air the cord is exposed to (i.e. how tightly is it coiled) AND what type of material the roll itself is made of.
If the cord is underrated and beat up and tightly wound onto on a plastic roll covered with a thermal insulating material like an old carpet, that is definitely asking for trouble.
If the cord correctly rated, in good nick, on a metal roll even partially open to the air then, using a 5" angle grinder will not represent a problem.

In fact I would go so far as to say that 30 m of unravelled extension cord in my shed would represent a serious trip hazard so keeping the cord on the roll when running an angle grinder probably represents a lower overall safety risk.
Power tool manufacturers will always say to unravel the cord but you need to remember they have to allows for the lowest common denominator ning-nong who cannot take all these factors into account .

This morning I ran 3A through the same 30m rolled up extension cord measured the temperature increase in the middle of the roll using a more sensitive thermocouple and after 10 minutes of continuous use it measured a clear increase of 2.5º which is ~consistent with what I saw yesterday. I might run the test for longer to see how high it goes.

I also should mention something that happened to me years ago (pre RCD days) when using a 50? year old extension cord on a Large Makita circular ripping 2" thick slabs. This cord was ~10m long and even though it was unrolled (I would do that anyway as that saw draws a lot of current) after using it for a couple of rips I noticed a hot rubbery smell and on feeling the cord noticed it was very warm and sort of soft and floppy. On opening up one of the plugs, the primary insulation was a rubbery stuff that could be almost crumbled by hand and it goes without saying that that cord went straight into the bin.

On a worksite these things usually get regularly tested but I wonder how often it gets done in a DIY situation?

Cheers Bob, very interesting to see the temperature fluctuations, considering I'm usually outside in full sun that could potentially cause a problem depending on the equipment I'm using.

No photos but I've been plenty busy this week. Got the new chute all mocked up in cardboard and I'm very happy with the way it turned out. This evening I spent some time putting the motor and it's mount back in the cabinet, was left with a good 3" of space between the new chute and the motor so I'm happy to move forward with the fabrication.

Still not sure now I'm going to cut the form out of the sheet metal but I'm pretty sure it's .6mm so I'm hoping I can get through it with some aviator snips. Bending it is pretty easy so I'll just be clamping it liberally and then hand bending with some sheet metal vise grips.

Up early again this morning, had a quick brekkie and then went off to Steel City to source some scrap and then Bunnings for some metal snips.







Was fairly surprised how quickly I was able to knock this out. Only took about and hour to cut the rough shape with the angle grinder and then remove the excess with the metal snips. Still have two more pieces to cut out but they are much simpler forms so shouldn't take too long.

For a mo I thought - whats the bit of PVC ducting doing in the middle of he work - only when I put my glasses could I see what it was

Haha yep a cup of tea is usually not far out of frame in a lot of my shots.

Just saw the face, looks like a new SP character, "Dusty"?

Couldn't help myself, it was screaming for a face to be drawn on it hahaha

And the last couple of pieces are knocked out. Cannibalising the freezer was a good way to get rid of it but next time I do something like this I'll just buy the metal new, too much time spent cleaning it up with a stripper disc.



Just spent some time cleaning up the innards of the cabinet where I'll be welding the chute in place, going to bend the forms tonight and then make the trip to my parents tomorrow to weld it all together.