PDA

View Full Version : bridgport sheave re-build



Rusty Marlin
08-21-2006, 03:21 PM
I have an old bridgeport and two of the v-gooves on the step pullys are worn to the point I cant' get proper belt tension. I was thinking of filling in the worn sheaves with somthing like like Devcon Steel Bed or other high end mechanical grade epoxy and then cut the sheaves back to nominal on the lathe.
Obviously I would have to mechanicaly key the epoxy to the sheave with under cuts in the existing sheave.

Has anybody here tried this, or heard about it?

tattoomike68
08-21-2006, 03:37 PM
Myself I would get a chub of steel or cast iron and build them from scratch like new.

An old friend of mine would run a metalizing build up spray system to add a hard surface then grind them back true again. It was spendy but so were the pulleys he was working on.

I realy dont know about the epoxy idea. It seems like a half a$$ed fix. I may very well be wrong about that.

Rusty Marlin
08-21-2006, 03:53 PM
They are dia cast aluminum pullys.

tattoomike68
08-21-2006, 05:32 PM
Machining them from a chub of aluminum would be easy. find some big chunks at a place that rebuilds hydraulic cylinder heads and pistons, they should have the stock on hand.

LarryinLV
08-21-2006, 09:38 PM
You could machine a couple of aluminum rings. Split them, insert the halves in your sheave and drill and screw them into the sheave core. Or just epoxy them in place, the pressure of the belt will hold 'em in and the epoxy will provide enough surface strength to keep 'em from spinning.

Use slightly wider belts if you can get them. They will ride higher in the groove once you fill up the depth, and provide drive from all three contact sides.

wierdscience
08-21-2006, 09:49 PM
You can do the epoxy,but it will only be temporary.Personally I would go with a chunk of aluminum like Mike suggested.

DR
08-22-2006, 10:10 AM
IIRC, those pulleys are fairly large, large as compared to drill press pulleys for example. At today's prices a chunk of aluminum to make new ones is kind of pricey. Then, you've got the hassle of machining them accurately and true running, balancing, etc, much easier said than done.


My solution would be to buy a small VFD, put the belt in a good set of grooves and vary the speed via the VFD. Probably cost about the same as a large chunk of aluminum. Of course, this assumes the B'port is three phase, which most are.

I see Online Metals gets $150+ for 6" diameter aluminum per foot. A 1hp capacity VFD can be had for less than the aluminum.

Rusty Marlin
08-22-2006, 10:38 AM
DR beat me to the punch line.
The fellas that are recomending to just make replacments havn't acctually had one of these apart I'm betting OR they have accsess to more, bigger, and industrial grade equipment like a plundge EDM.

The material alone is going to cost me more than a new set and if I could drop the cash for new set I wouldn't be interested in reparing what I have. (Circular logic sucks.)

Besides a couple of other techinical dificultys, like a blind pocket face spline for low gear(EDM work), and a full length drive spline that would take a much bigger shaper than I can get a hold of to cut, or it would need to be broached or EDM'd.

I think Larry has the best approach for repair so far.

pcarpenter
08-22-2006, 11:45 AM
I don't know if this is really a valid option, but I might be tempted to clean up any sharp edges that may exist from the existing wear (in a lathe) and try some of the link-belting material.

Fenner drives makes one product called Power Twist that is for use in stuff like this as well as some other stuff that is riveted together. The power twist stuff will conform, and may solve your contact problems. You can mail order the stuff from lots of places (Grizzly, Enco, etc) or your local bearing supply place may well carry it or a competetive product (mine does).

I haven't installed it yet, but plan to use this on the dual-belt drive on my lathe. It has a bit of give and makes for really smooth running and less harmonic transmission from the motor to the driveline, although just a wee bit of horsepower may be lost.

Paul

alabamaed36046
08-22-2006, 08:37 PM
If there is enough meat behind the pully grove I would turn the grove off completely.Get a new pully bore for a light press fit and grub screw together.
Look at an auto junk yard / repair shop. Might find a suitable pully fairly cheap.
alabamaed36046
P S Just remove only the worn pully of the step pully.

wierdscience
08-22-2006, 09:06 PM
DR beat me to the punch line.
The fellas that are recomending to just make replacments havn't acctually had one of these apart I'm betting OR they have accsess to more, bigger, and industrial grade equipment like a plundge EDM.

The material alone is going to cost me more than a new set and if I could drop the cash for new set I wouldn't be interested in reparing what I have. (Circular logic sucks.)

Besides a couple of other techinical dificultys, like a blind pocket face spline for low gear(EDM work), and a full length drive spline that would take a much bigger shaper than I can get a hold of to cut, or it would need to be broached or EDM'd.

I think Larry has the best approach for repair so far.

I have had more than a few apart,the splined section presses out once the spanner nut is removed from the top and as I remember the bore is just keyed in.
There is another option,take both pullies and use the lathe to skim cut the grooves a little deeper until they clean up,then go with a shorter belt,or a Fenner belt like mentioned above.

Or,here is a bizarre idea,check into some new parts,or at least look at the exploed view of the head-

http://www.machinerypartsdepot.com/site/1478157/page/552090

Rusty Marlin
08-23-2006, 09:12 AM
If I could afford new parts I would buy them in a heart beat.
Right now the link belt ist he cheapest, quickest and easiest. If that doesn't work I'll look at other options.
Thanks for the alternative ideas

Wirecutter
08-23-2006, 11:09 AM
I've used the "link belts" and I can say that they're good stuff. When you change the number of links, remember to first turn the belt inside-out. I also like to have a pair of needle-nose pliers onhand.

Link belts are a bit more expensive than regular ones, but they're very handy to have around, and they hold up well. I keep 6 feet or so in my toolbox just in case.

I've also made pulleys, and it's not so hard. I used a similar pulley as a guide for getting the cutting tool profile right. Chunks of aluminum the size of a Bridgeport pulley "blank" are pretty expensive - the pulleys I made weren't quite that big. The recessed spline for the high speed setting would be a trick, too.

Do you have access to a TIG, or a friend that does? Could you build up the aluminum with a weld and machine that down?

-Mark