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Variable speed changeover progress

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Variable speed changeover progress

#1

Variable speed changeover progress

Don Henthorn

>Well, I am finally getting with it and it is not going too bad. I started out with a piece of plywood that is an inch short just as Mark's cabinet top was. I went to HD to get a larger sheet and when I saw the price and the product I changed my mind.

There is nothing hard about the project. I lucked out in that the pulley and the motor mounting clamp slid into the cavity without having to grind any metal off the belt changing opening. I did have a problem with the motor mount that was jury rigged at the last minute so the motors could be shipped. As the pic below shows the "craftsman" who welded the joining patch on didn't much care what he was doing since he wouldn't have to deal with it.















If he had welded the patch on the top everything would have been cool. As it was the welds were even lower than the patch making the motor sit on a slant if the motor was fastened down through the slots which are for that purpose. I filed the welds down flat and inserted 1/2" washers under the mounting slots. The washers are about .002 thicker than the plate which makes the motor sit flat on the mounting plate.

I elected to keep the original switch which will mean the controls will not both be on the stalk, but I can live with that, in fact I think I will like it better.

I am looking for a fan and can find lots of them but the ones I find don't have filters on them. I have decided to just stretch a layer of nylon hose over the intake side and try that for a while. I still have to build the box for the motor and controller and mount the fan wnd wire it in when I get it and build the stalk for the potentiometer.

Still haven't a clue as to how I am going to determine the speeds for marking the dial.

I like the setups where the motor is under the lathe in a cabinet, but at my age getting down to work in a cabinet is a real pain. Mark's setup has some things I like better than the cabinet, so I am not disappointed.

Thanks for listening.

Re: Variable speed changeover progress

#2

Determing speeds for dial

Jeff Gerardot, Indianapolis IN

>(Wow, this got long-winded. Sorry)

Here's an idea for a low-tech approach. It's not super accurate, but I think it will get you close enough.

I have not done this myself. If anyone spots an error in my thinking, feel free to speak up, I won't be offended.

The basic idea here is to make the lathe traverse a distance for 1 minute and then you measure that distance and back-calculate to deduce the RPM. Since you want the lathe to stay in one place, you can "traverse a distance" by making the lathe power a long belt while you count the rotations of the belt.

You'll need:

-- a homemade belt of specific length

-- 1 homemade wooden pulley

-- 1 other pulley, can be homemade or one you've got in stock, just has to spin freely.

-- (optional) hand tally counter

-- a stopwatch or clock with second hand

-- an assistant to watch the clock for you

One idea for the belt material would be string.

You'll need to make 2 wooden pulleys for the string. One pulley will stay mounted in the lathe, this one must be a fairly precise circumference, like 3". The other pulley's size doesn't matter, just make it 4 or 5 inches.

It's important that the belt not slip during the counting process. Perhaps some sticky coating on the wooden pulleys, or even sandpaper?

I think a lathe pulley with 3" circumference (.95" diameter) and a belt length of 60" would work nicely.

Leave one pulley on the lathe. Mount the other pulley in a plane with the lathe pulley at a distance to take up slack as necessary. Put the string belt on the pulleys and pull it tight enough that it won't slip. Place a tag/sticker/tape on the belt string or mark it in some other way so you can count revolutions.

Start the lathe, proceed with caution 'til you know things won't go awry.

Make sure the belt is not slipping.

Take the lathe to a speed you want to measure. When your mark comes to a visible point on the pulley, yell "go" to your timing assistant to start the stopwatch. Every time the mark comes to that same point, you count (or click your hand counter). When your assistant yells "stop" at 1 minute, stop counting.

Now you've got the data you need to calculate the RPM of the lathe at that dial setting. Like this:

lathe rpm = (belt length inches / lathe pulley circumference inches) x your count

So if you use the sizes I suggested, it'd be

rpm = 20 x your count

This ought to handle the meaningful speed ranges for a lathe.

Hope this helps.

Re: Variable speed changeover progress

#3

Use a tachometer ! *LINK*

Fred in NC

>Cheapest tachometer I have found... and it was designed for use in a lathe.


Lathe tachometer

Re: Variable speed changeover progress

#4

Re: Determing speeds for dial

Don Henthorn

>Wow! Jeff, that sounds like it ought to work, but I am 85 years old. I may not have enough time to finish the process. (G) Never-the-less I'll keep that in mind just in case I can't find a hand held tachometer to borrow. Thanks for the suggestion.

Re: Variable speed changeover progress

#5

Re: Use a tachometer !

Don Henthorn

>Thanks, Fred. I'll check it out if I can'f ind something to borrow.

Re: Variable speed changeover progress

#6

Re: Variable speed changeover progress

Stuart Johnson

>I don't want to sound like a smart a** but I don't see what difference the rpm makes. If you start very slow and ramp up to the correct speed for what you are turning other than curiosity does it make any difference if you are at 100 rpm or 2100 rpm?

Re: Variable speed changeover progress

#7

Actual RPM

Fred in NC

>True... I never worried about the actual speed, and I can pretty well figure if it is too slow or too fast for the operation. What really matters is the surface speed. Or put another way, bigger diameter = less RPM for the same surface speed.

For temperature measurements I always used a THUMBOMETER !

The only reason for knowing the APPROXIMATE speed is repeatability. I bought my tachometer for my metal lathe, and will use it to calibrate the pot for my Jet Mini. Otherwise I could not justify spending $40 on it.

Re: Variable speed changeover progress

#8

Fan Filters

Fred in NC

>Hello !

For the 4" fans, I use a piece of:

VENT FILTERS - Electrostatic Register Filtration... from WalMart.

They sell in a pack of 12 - 4"x12" for about $2.50. They are about 3/16" thick.

They seem to do the job, and don't restrict the air flow too much. Actually, I put some on the heater vents too...

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