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New motor, pulley, and linkage for my power hammer


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Now that my power hammer is sitting on its new home and securely bolted to the new foundation, I am working on fixing the other minor issues that it has.

 

Originally it has been setup with the motor hanging off the side, going to a countershaft mounted above the hammer, and then to the rear pulley, to slow down the speed of rotation. This is a bit janky and unwieldly, and the jurryrigged idler pulley for the slackbelt clutch isnt the most responsive.

 

In order to fix this I will be making a new motor mount to mount the motor down low and behind the hammer, building a new idler arm for the slack belt clutch, and fabricating a mount for it, and re-building the treadle linkage.

 

I first found myself a proper 900 RPM motor, as the original spec called for in motorized fairbanks power hammers as opposed to lineshaft driven.

This motor is ginormous, over 100lbs and easily twice the size of the motor that was on it, but it's still actually only a 2hp motor. I've got a large angle bracket which I will drill and tap the rear column of the power hammer in order to bolt down, and then due to the size and weight of the motor, I will probably have a rear leg at the back of the shelf going down to the floor as well. I already have a 3 inch pulley with lips on the edge which will be used as the tensioner / idler pulley.

 

pulley1.jpg

 

The rear pulley is 13 inches in diameter, which means that the motor pulley should be 5 inches in diameter to get the specified 350 BPM. Herein lies my first challenge. I have looked everywhere, and can not find a 5 inch crowned drive pulley for a 2.5 inch wide flat belt which will fit on a 1 1/8 motor shaft. Thus my first bit of work is to make a new drive pulley.

 

I bought an aluminum round 5 inches in diameter and 6 inches long to be my pulley blank. In order to turn the face of the pulley concentric to the motor shaft, the first thing I had to do was create myself a mandrel the same diameter as the motor shaft to mount the pulley on once I have the center bored and reamed to 1.125 inches.

 

I chose to make the mandrel first. For the mandrel, I have a piece of 2 inch round stock which has already been drilled and tapped for half inch 13 on the end (and had part of it turned down for some other job, but that can be ignored) I've done very little machining, even though I've had my lathe for 9 months now. Getting objects perfectly centered is still a bit of a chore, but I got the 2 inch round almost perfect, so I felt that I was off to a good evening in the shop =)

 

 

My lathe is an 1890 Prentice Brother's lathe and has no gradations on any of the dials, and only horizontal feed, no traverse. I run it nice and slow and take my time, and a lot of measurements. Once I got really close to the final dimension I was barely skimming a thousandth off the top to zero in on 1.125.

 

pulley2.jpg

 

 

After this cut it read 1.126 on my digital caliper, and 1.124 on my old brown and sharpe vernier scale caliper. Not bad for an ancient hunk of iron, although it took me a large number of passes. Good thing I dont have to make money doing this !

Edited by Justin Mercier
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Next up was to get the blank centered. The 6061 aluminum was left with the mill finish and was not perfectly round to begin with. I wrestled with it for 10 minutes in the chuck, and this was as close to centered as I could get it. Next I'll first face off the front of the billet, and then drill out the center with a large but slightly undersized drill, and then I will ream it out with a 1.1250 reamer. With that done I will re-center the mandrel, and then mount the pulley on the mandrel, tightening it down with a half inch bolt and a big washer. Then I will skim down the face so it's concentric with the outside, and then put a crown on the pulley.

 

 

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Facing off that blank ended up taking 2 hours by hand. With no cross-slide traverse, I had to sit there slowly cranking for every cut. Gives you greater appreciation into the work that went into early machining. I didn't finish drilling the first hole in the center yet, because as my bit got deeper, and the friction at the edges of the hole got better, my chuck started to spin in the tail stock. I then went digging around to see if i could find my MT3 reamer to hone out the tail stock and get it to fit, but I couldn't find it, so then I went looking for a large dogleg to hold the bit from spinning, and couldn't find one large enough either. Tomorrow morning I'll have to either shim the shank with a tiny bit of paper or tape, or find where my big dogleg is to keep the chuck from spinning, so I can finish this hole, and move to the larger final size before reaming it out.

 

pulley3.jpg

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I ended up using the old metalworker's trick of using a lathe dogleg to keep the chuck from spinning.

 

pulley4.jpg

 

 

Once the holes were drilled I reamed out the pulley to 1.125 I actually only ran the reamer down about 4 inches and then decided to cut off the first pulley before finishing the hole.

 

pulley5.jpg

 

I used a cutoff tool to split the large billet exactly in half and face off the back and front of the pulleys at the same time. I re-inserted the last drill (which now didnt actually touch the reamed out hole) partway through just to catch the pulley when I got through.

 

pulley6.jpg

 

With the first pulley cut off, I finished reaming the hole on the 2nd.

 

pulley7.jpg

pulley8.jpg

 

The pulleys fit perfectly over the shafts on my motors. The shafts themselves are just a tiny bit undersized so they slide on and off without needing to be pressed in place. Next up is to skim the outer edges concentric to the holes using the mandrel that I made, and then crown the pulleys, after that I need to broach a key way and drill and tap a hole for a set screw in each of them.

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Took the sized and holed blank around the corner to my friend's shop to use his press to broach the keyway

 

pulley9.jpg

 

with the keyway broached, I mounted the pulley to the mandrel and turned the outside flat and concentric with the middle. Since I dont have a way to turn a taper or radius, I will probably just turn a series of small flat steps on each side of hte pulley and then blend them with a file on the lathe.

 

pulley10.jpg

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In doing some reading, I found out that I dont even really need to blend the steps as long as they're not sharp, so I changed the angle of my cutting tool to give me a bit of a sloped cut and crowned the pulley with a series of steps. The crown is slight, but should be more than enough. Standard crowns for a flat belts pulley is 1/8 per foot. With the crown turned, the last step is to drill for a set screw.

 

I'm going down all the way with a 5/16 drill and then half way down with a 3/8 drill, then tapping the bottom half of the hole to 3/8 for a big brass set screw. There are two philosophies for set screw location. One is that you put the set screw over the top of the keyway, and the other is to put it exactly opposite, I'll be putting mine opposite.

 

To find the top of the of the pulley to have it centered on the drill-press for drilling, I borrowed this simple but nifty tool. You put it in the chuck and it's got a V on a pivot, above the pivot is a point with a line, and a line on the bar you put in the chuck, when they're lined up, you're over the center.

 

pulley11.jpg

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I now need to work on building the mount for the motor now behind the hammer, and to create a pivot arm to mount to the back of the hammer for the tension idle pulley. For a gauge of the size of this new motor, here's the motor sitting in front of the 5hp motor for my phase converter, even though it's only 2hp. The heavy duty angle bracket I have may not be heavy duty enough to hold it up!

 

3phase.jpg

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A little late now since you have the beast of a motor, but why not use a smaller motor (2 HP, 3 phase are pretty small) with a VFD to get the right rpm?

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I was using small 2hp with a KBAC27D vfd originally, the problem is that with a VFD while you have constant torque, you dont have constant power. This is the reason that it was set up with a 17xx rpm motor + some line shafts to reduce speed, because to run the motor at half speed directly to have the right speed means I was only running around 1hp and it would have trouble turning over with the large inertial mass. I wanted to get rid of the extra line shaft pulleys and whatnot and put the machine back to the original configuration. Doing so also lets me remove the rear pulley from the machine when needed to service the broken brake without having to take the whole shafting off the way it was configured.

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Ended up getting a different motor for the RPC, as the motor that I was using had some problems with it, and didnt start up smoothly. Got the motor mount built this weekend and mounted behind the hammer, I havent drilled the final mounting holes for the motor as of yet, and am just using welding vice grips so that I can get the position perfect for the belt tracking before I put anymore holes in it. Originally I was going to mount the motor lower, but because the hammer is not the new frame type with the pass through hole, it doesnt actually need to be any lower, and a shorter belt makes getting the tension right easier.

 

All that's left now is to get the bolt holes for the motor mount drilled, and then finish fabricating the tensioner arm with idle pulley,.

 

motormount.jpg

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  • 2 weeks later...

I assembled the new linkage today, and i'm hoping that I didn't make a mistake with my motor. The linkage and idler work fine, but... even though it's been running on a 2hp motor for a while, but in such a way that the motor itself would keep spinning even if the top shaft that it was running to was stopped., i think this new configuration is more stressful on the motor itself, maybe because of the lower RPM of the motor, so it doesnt have it's own momentum. If I step too hard on the treadle, it stalls out the motor, as it doesn't overcome the 'stopped' inertial weight of the hammer itself. if i step down real slow and let it pick up speed, it then runs fine however. I'm going to swap out for one of my higher speed 1750 rpm 3hp motors and test if the extra 1hp makes a big difference in starting against the heavy inertia of the hammer top shaft and ram.

 

tensionarm.jpg

 

IMG_2032.JPG

 

IMG_2034.JPG

Edited by Justin Mercier
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I bet a steel drive wheel would fix it. The aluminum isn't heavy enough to provide a flywheel effect. You could always bolt a small steel flywheel to the face of the motor pulley, but be sure to do it on the lathe and balance it.

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Yeah, I wonder if the rotating mass of the old jackshaft is what let it function properly. The original setup with a top jackshaft was as below

 

DSCN2140.JPG

 

I was planning on simplifying things greatly by direct driving with the proper speed motor. Because it had been running fine on a 2hp motor, I just got another 2hp motor, though the documentation for the hammer says it shipped with a 3hp 900rpm motor. I'm going to wire up one of my 3hp 1725 rpm motors today and see if that overcomes the issue. Otherwise I may end up having to add a jackshaft similar to this fairbanks below

 

DSC00988.JPG

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On facebook in the powerhammer group another fairbanks hammer owner suggested much the same thing, that eliminating the jackshaft has got rid of the flywheel effect that allows the hammer to pick right up from a stop. As much as I was hoping to eliminate jackshafts entierly, I may have to put one back into the system just to save rotational momentum. He said that with a 5hp motor direct drive, it was very slow to pick up, which is the problem I'm having now, but that he was able to drop to 3hp by adding jack shafts with heavy pulleys. The 'original' motors shipped with these hammers were GINORMOUS monsters of motors for their rated HP, so they had a tremendous amount of rotational mass in and of themselves. Modern motors are much much smaller and lighter.

 

Roger Smith - I
had a 5hp 1725 rpm motor on my 100lb'r originally and it was still very
slow to start. As you can see in the pic the tension pulley is on
right. The hammer turns clockwise. This does make a difference. Since I
went total line shaft the momentum built

up in the spinning pulleys snaps the ram right up but also allows
excellent control. If you have room above the hammer I'd suggest a jack
shaft with an extra pulley or two to store energy for the initial lift.

 

10609547_979098348773146_842766999027588

 

Roger Smith - I run the entire line off a 3hp motor btw. The hammer doesn't bog it down the least bit.

Edited by Justin Mercier
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Yep! Roger is a good one for that stuff. The sheer amount of angular momentum available in a lineshaft setup is incredible, which is why you can run a whole shop on a tiny motor. Is he still using a gas-powered hit-and-miss? Those things have incredible torque as well, what with the big heavy flywheels. Kind of inconvenient for your setup, of course. ;)

 

A flywheel somewhere in the system is the way to go for you, I'm thinking. Ten to fifteen pounds of balanced steel on the motor pulley ought to do it. A jackshaft would work too, but it has to have the mass to keep things going. That's why Little Giant-type hammers can run directly off a small motor, the main shaft pulley is a massive beast of a cast iron flywheel. The one on my 50lb Star is 11" diameter and three inches wide, probably weighs around 30 pounds. Never any trouble with a 2hp motor, it'd probably run off a 1hp as long as you let it wind up to speed before hitting the treadle.

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I just ordered parts from McMaster to build a new jackshaft similar to
the one pictured above. I also have a 50lb flywheel which will fit on
the end of the jackshaft that I can add to give it some real momentum.
The shaft will be 1.125 to match the pulley I made, and the 4 inch
double Vbelt pulleys I already own, so I can drive the shaft 1:1, the
flywheel has an inner diameter of 1.165 so I may have to slip some shim
stock in it before I tighten down the set screws. It's an old 22 inch
diameter 3 step pulley from a treadle lathe, which made its way into my
house while I was restoring an 1880s barnes velocipede lathe. It wasnt
the right size shaft size for the lathe, but I'm glad I held onto it
now.

 

flywheel.jpg

Edited by Justin Mercier
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Yeah, i'm going to have to be careful with it until I see if it'll work at 900 rpm. I dont want to pull a Sam, and power something too fast and have it come apart and blow up. If it looks dangerous, I'll probably have to find myself a big billet of solid steel and bore and ream it to 1.125, throw a keyway on it, and a pair of retaining collars on either side for a flywheel. I have this one sitting around though, and the shaft size on it is almost right what I need, just need to wrap a piece of 20thou shim stock around it. so hopefully it'll work =)

 

I know it'll do 300 rpm quite easily, as i could pedal the treadle lathe at 5 revolution per second, and it's a sturdy casting. I'll power it up with my hand on the cut off switch if it wobbles or vibrates at all, it'll be cut off =)

Edited by Justin Mercier
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McMaster managed to get me the shaft and pillowblocks that I ordered to me today, so I started planning out the reconfiguration.

 

I was originally looking around my parts bin for a big hinge to hang under the mount that I already had fabricated, but then I thought of something better. I have a motor mount plate already which is pre-drilled with the holes to fit a variety of motor frames, and rather than attaching that to a giant hinge... I'm going to run a pair of angle iron bars across and bolt those to the current frame and then I can hang 4 bars of 3/8 all thread and run them through the motor mount plate, which can then be hung directly below. This will allow me to use both the weight of the motor for belt tension, as well as locking the position there and allowing for adjustments when the belts stretch. In addition this makes it so that I'm not tied to any particular motor, as the base plate will mount almost any motor, and with the shaft above it, if I swap to a 1750 rpm motor for example, I need to just double the pulley size on the shaft, and then I can adjust the motor height to keep the pulley fitting . I'm using an H type pulley hub on the shaft so that if I do swap motors it will be simple to swap out the jackshaft pulley and retain 900rpm on the drive pulley.

 

Measuring the center height of the pulley position, I need to put 3 inch riser blocks under the pillow blocks to match the same location for the drive pulley, which gives me plenty of clearance under the jackshaft to put some angle iron across the top for suspending the motor mount plate. I'll then cut the angle iron at the top short, letting the pulleys on the motor and the jackshaft hang just past the end of the mount, and then just beside that that I will mount the flywheel. I want the the pillow block as close to the flywheel as I can, and I may end up adding a foot underneath there to help support the weight too.

 

plan.jpg

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I just re-did the pulley math for how the hammer WAS running with the old setup, and it was actually set up to run QUITE a bit slower than the rated max BPM, and a lot slower than I thought that it was running. There was a 5 inch pulley on the 2hp motor hanging off the side, this ran to a 12 inch pulley on the top shaft, the drive pulley on the topshaft was only 3.5 inches in diameter. With a 1750rpm motor that means the top shaft was rotating at 730 RPM, and then with a small pulley at 730RPM going to the 13 inch pulley on the hammer, the hammer was only running at 200bpm, which was actually quite comfortable. I may just stick a 6.75 inch pulley on the counter-shaft instead of doing a 1:1 ratio with the pulleys, to slow the counter shaft down to 533 rpm (and slow down the speed that I'd be spinning that big flywheel to a safer level) 533rpm on the 5 inch drive pulley would get me to 205 BPM for the hammer, right around where it was previously.

 

I found this nifty site http://www.blocklayer.com/pulley-belteng.aspx which is great for calculating the belt length needed, and the distance between centers of various pulley combinations. The suspended motor plan from above makes changing pulley sizes wicked easy.

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very interesting thread. I am about to set up my kingshorn 90lb hammer and have bought a 3hp 710rpm and 5hp1430 motor for it. I am hoping the smaller motor will run it then I could run that through a single phase inverter controller.

It had a flywheel on the hammer so I am hopeful.

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In a shop where I work sometimes, my friend has got a 100 lb. Howe mechanical hammer running on a 3 hp motor, with a jackshaft setup including a fair amount of spinning weight. It works well, powers that hammer right up. That hammer was designed to run off of a lineshaft, and actually until reading this thread I hadn't considered that the flywheel/jackshaft added later on by whoever did the electric conversion actually does a lot more than achieve the right speed at the hammer clutch.

Most educational!

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