Motors to drive tools

Hi all,

I have recently acquired a Kennedy Power Hacksaw which is the v-belt drive version, i.e. to run off an exisiting motor. I am having trouble sourcing a suitable motor to power it. I have a 1425rpm motor 0.25 or 0.33 HP but the speed is too much for the saw, hence I have to either reduce this down or find an alternative motor. Rather than spending insane amounts of cash.

I was thinking if I could source a gear box but searches on the net are proving fruitless. Alternatively is to make a worm style gear to reduce it down. But before I embark along the incorrect avenue, I was wondering if any of you have an idea on how to achieve a reduction without it costing the earth.

Some stats, my motor is 14 mm shaft, and the pulley on the saw is 4 inch, the saw needs to be driving itself at around 240 rpm. I'd need a very small pulley for the motor to do it with the current pulley on the saw (can't find one and would have to make one, but I think it is too small for the shaft and good operation of a v-belt). The pully on the saw is 1/2 v-belt. The manual for this is on this site:

**LINK**

Thanks in advance,

Andy

Michael beat me to it.

Countershaft is the way to go - the clue is on the second page of your link.

Small(ish) pulley on the motor driving via v-belt to larger pulley on contershaft, then small pulley on contershaft driving via second v-belt to the pulley on the saw. By playing with the pulley sizes you can get just about any speed you want on the saw.

The motor you have is fine for size.

Keith

V pulleys with a blank bore here.

Thanks Michael and Keith, I've looked into it and I figure if I run the following arrangement it should work well:

2 inch drive to 5 inch countershaft 1425 > 570, then 2 inch to 4 inch (saw) = 230 rpm ish.

Now to source the parts, many thanks for the advice.

Best

Andy

Machine Mart seem to do the same range. Though a bit dearer, they might save on shipping if a nearby branch has them in stock.

(another) Andy

`Hi `Andy

I owned an original motorised Kenedy hacksaw.It had a flat belt and was driven directly off the shaft which was crowned and a cut off switch on the motor.It worked well but having obtained a bandsaw I gave it to a mate.

Regards Francis

The Kennedy we had in the departmental workshop also had, like the one bricky refers to, a flat belt drive. From memory the pulley on its 1/4 HP "square" Hoover motor was around 1" diameter and crowned but the saw pulley was a simple flat section approaching 8" diameter.

Given the faff factor in making a countershaft and the effectiveness of multi Vee belts on large diameter flat pulleys it may well be easier / cheaper to find a small multi groove pulley for the motor and cut a suitable size flat disk to go on the saw. Older washing machines, spin driers and small electric mowers are potential donors of useable size motor pulleys. If you have a micrometer setting bed-stop its very easy to make a multi-groove pulley. A simple Google search will soon turn up a site or catalogue listing with the groove size details. Small pulleys aren't exactly expensive if you insist on cheating!

Clive

Have to agree with Clive.

There never was a V-belt version of the Kennedy, they were flat belt drive, which needs to be "bar-tight"

The drive "pulley" was little more than a crowned sleeve over the motor spindle,just under 1" dia (say 22mm today) and the saw pulley was flat 6" dia.. This gave a ratio of a little under 7 : 1.

I wouild suggest an unusual and technically incorrect solution, put a small pulley, say 1¼" on the motor, and a 7" pulley on the saw spindle, but use a round section poly drive belt, which will fit into the bottom of the pulley V's, so will have contact on 3 sides, left, right, and bottom. This will probably give a decent ratio for a 1425 rpm motor.

Don't all explode at once!

Phil

Odd then that the Kennedy brochure in the link in the original post talks about a countershaft and v-pulleys.

Keith

Edited By Keith Long on 12/05/2013 23:08:48

I agree with Clive Foster ... PolyVee is the way to go.

For this application; their particular advantage is that they will handle BIG reduction ratios.   You're only looking for 6:1 reduction ... That's comfortably within their capability.

MichaelG.

Edited By Michael Gilligan on 12/05/2013 23:37:58

Typical Spec. from Goodyear.

and ... an excellent Design Guide, from Conti.

MichaelG.

Edited By Michael Gilligan on 13/05/2013 08:31:24

Hello Andy,

Just as a matter of interest for you.

I am halfway through building a Kennedy clone courtesy of Myfordboy from whom I purchased the plans/drawings.

His version uses a 1/3 hp motor (4 poles of course to give 1450 rpm)

He uses a 6" dia pulley on the crankshaft and a small dia toothed pulley on the motor, the crankshaft speed being about 210 rpm. He also uses a toothed timing belt for the drive but with no teeth on the large pulley.

This large pulley is available for purchase from him.

It's worth looking at his youtube clip to see it in action, quite impressive it is as well ( I think he wears safety shoes)

The clip link is **LINK**

It has been discussed on this forum before, search for powered hacksaw or "myfordboy"

Len. P.

2 more ideas- use bike chain and sprockets, poly vee belt or timing belt and make the big pulley from plywood.

Thanks for all the replies, I am thinking simplicity over cost and I like Len's suggestion to follow the pretty impressive myfordboy saw pulley system, or go the poly v route as the part count is much lower than the countershaft approach. I am looking into this. Originally I came across RDG single v-belt pullies, which appear to be cheaper than machine mart etc but would need 2 inch drive to something like 9 inch on saw, too big to work.

Gordon, I want to stick with pulley and belts rather than sprockets and chains for simplicity (although it's probably just as easy).

I will post back when done!

Thanks

Andy

I'm a convert to poly-vee belts. If I covert my lathe to a VFD, I will use a poly-vee.

> You're only looking for 6:1 reduction

On our old tumble drier the reduction was around 30:1, pulley around 3/4" the balance around the nearly 2' drum.

Neil

You should be able to run a size A V-belt from a 2" pully to as big pully as you like quite easily, if you are worried about not enough wrap round on the small pully, you can use a jocky pully to bring the belt further round the pully. On the machine that I built the motor had a 2" motor pully, to a10" (I think)pully on the jack shaft, the drive from there was by gears, can't remember the ratio, all the pullies, gears, motor came from a washing machine. Owing to the materials I had, the saw frame, instead of sliding along a bar, it was suspended on two connecting rods, and swung back and forth. Ian S C

i have one of these kennedy saws which i use for cutting small bits and pieces which the bigger bandsaw is too large for

i have a flat belt, rightly or wrongly, running directly on the motor spindle and a 6 inch plywood drive wheel [cos i didnt have any ali there big enough to make a flywheel]
works nicely, runs nice and slowly, and seems to be the right speed for the machine. I have the original hoover motor on mine.

nothing complicated
works as expected
every expense spared

Z

Edited By Ziggar on 14/05/2013 20:18:28