Old chinese pneumatic hammer

[westerwald]

This is the hammer I am working on. Any new info is welcomed.

[nonjic]

That motor pully looks enormous, I would check the motor speed before I turned it on! you should be looking for about 220 - 240 rpm at the flywheel.

[westerwald]

John are you referring to the flywheel on the Hammer? I want to be sure. The only thing I have had to go from is a very hard to read chinese manual. My Dad has said several times that drive pulley seemed too big.

[Mainely,Bob]

Not John but,the pulley on the motor needs to be MUCH smaller to get the RPMs at the flywheel he`s talking about.
First look at the motor plate and see what the motor runs at.Most are either low speed(around 1700 RPM) or high speed(twice the low rated RPM or approx 3400).
Then measure the diameter of the flywheel on the hammer.
Go to one of the sites you can Google here on the web that has a table to plug in the info you have(the motor RPM and the flywheel pulley size)and find the motor pulley size you need.
If you have a higher speed motor and can`t reduce the motor pulley size enough then your choices are either replace the motor with a lower speed motor or run a jackshaft system to reduce the RPM.
Hope this helps.

[clinton]

http://gadi.agric.za/software/renting/pulley.php
try this for pulley size

[westerwald]

The big pulley on the hammer is 79 1/2 " Dia and my motor is 1760 rpm.

[westerwald]

After calculating I have come up with these numbers.
10" drive =221 rpm
10.6 =232
10.75 =237.6
11 =243

Please feel free to add to this or correct. What is the ideal speed? Is closer to 240 rpm better? Thanks guys

[Don Hanson]

The big pulley on the hammer is 79 1/2 " Dia and my motor is 1760 rpm.

You need to re-measure, the pully does not look like it's over 6 feet in dia. :)

[westerwald]

Sorry I meant circumference. The diameter is 25 1/2 " I started over with the correct number. If I am right I need a 3.5" drive pulley to get 240 rpm?

[Don Hanson]

Sorry I meant circumference. The diameter is 25 1/2 " I started over with the correct number. If I am right I need a 3.5" drive pulley to get 240 rpm?

Now that sound about right.

[nonjic]

From memory, the pulleys are usually around 5 to 6" dia (for a 40 kg hammer), but this is the kicker, thats on a 6 pole motor (960 ish revs @ 50hz)

My gut feeling is that motor will be neither use nor ornament without a backshaft, as you wont get a pulley small enough diameter to give you the flywheel RPM's

220 rpm will give you better light blow control, 240 rpm much more top end power.

Dont run it faster than 250 rpm as funny things start happening with the air inside the hammer, and it wont work right.

[Jamesrjohnson]

Banjos. I would go with a 3" pulley. That will give you 207 rpm at the hammer and a very controllable hammer. You could go 3.25 and get 224 rpm. My preference is a little slower and.more control.

[Dave Hammer]

Please be aware that using a small pulley (directly) to drive a large pulley isn't always a simple matter of calculating pulley diameters.

Each application has a minimum "belt surface" contact requirement to work. For example, you probably couldn't drive a machine which requires a ten horsepower motor with a two inch pulley on the motor and a twenty inch pulley on the machine (even if you could find a two inch pulley that would fit on a motor that size). There probably wouldn't be enough belt contact on the small pulley to get the machine started. The motor pulley would probably spin without moving the belt (and ruin the belt).

I expect this type of requirement is part of the reason slower RPM motors are used with some applications (where the designer doesn't want to use a jack shaft to reduce the (driving) RPM).

A conversation with a technical support representative at an industrial supplier (such as Applied Industrial Technologies or Motion Industries) will help you determine what the minimum belt contact (on each pulley) will work on your application. How far around the pulleys the belt is wrapped is significant in this calculation.

If you have a copy of "Machinery's Handbook" (and a mechanical mind with great patience), you may be able to find the information in there also.

[Jamesrjohnson]

Have had second thoughts on my last post. I did a simple math calculation utilizing motor speed and pulley size to get to a good hammer operating speed. The problem may be finding a pulley that diameter that will fit and then worry about belt slipping at that motor rpm. On the anyangs the motor rpm is in the 1150 rpm range.
Looks like the hammer is cleaning up nicely. I emailed the pictures to anyang and they said it was a smaller company that is no longer in business. These kind of hammers have a long life and are simple to do what little maintenance there is. Keep us posted on your progress

[nonjic]

I would make up a set of wedges to go between the anvil block and the frame of the hammer. Try and bed them reasonably well, and leave them stuck proud 3 or 4". You can then 'follow them up' as you use the hammer for the first few months.

Once they have settled, and are tight you can chop them off flush, and put an angle iron 'cap' over them for a neat job.

[westerwald]

Would these wedges be wood or steel? I pictured oak but at this point it is obvious I need all the input I can get. Thanks again for all the help!

[nonjic]

oak will be fine :D