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John Stevenson
03-16-2011, 07:52 PM
Well after doing countless literally hundreds of Bridgy motor shaft repairs mine has started making ominous noises as it goes thru the range.

Anyone know anyone who does a decent repair :D I can't do it because the mill will be in pieces :rolleyes:

No joking aside I'm seriously thinking about doing a transplant and swapping the 1 1/2 HP motor for a 3 HP and getting rid of the sheave drive and fitting a single speed poly vee drive with VFD

Got a brand new VFD but it's 440v in, 440 volt out which is no problem as the mill is 440 volt anyway.
The rewind people will literally give me a 3HP motor just to get me back running so all it's going to take is two pulleys and a belt.

If I fit a 1425 rev motor [ standard here for 50 Hz ] and run 1:1 that will give me 3,000 revs at 100 Hz and 430 revs at 15 Hz

Sound OK ?

spkrman15
03-16-2011, 07:58 PM
I think 435 rpms is high for a low speed. Not sure what work you do with your mill, but i love the fact i can slow mine down to about 5 rpms. I have a variable speed and a VFD. Can you get a variable speed instead of the one pulley?

Also my electrician told me to keep the minimum setting for the VFD at 5%.

1. Your motor could be on and you would not know it if you settings go to 0

2. The VFD will still be working, causing heat and maybe damage.

Rob :)

PeteF
03-16-2011, 07:58 PM
Go for it John, you'll wonder why it took you so long to go down that route. However at extremely low RPM the motors typically run out of grunt, so you may find you'll still have to sometimes take the mechanical route and swap pulleys or whatever your particular magnificent example of engineering excellence that you hold in such high esteem uses. While I have VFDs on all my machines, I've really only experienced this situation with my lathe, where I will very occasionally flick in the back gear and crank the motor RPM back up to useful output. I can certainly see the scenario with a mill however, it's just that mine is so miniscule I haven't yet needed to use the back gear on it.

Pete

John Stevenson
03-16-2011, 08:10 PM
Remember the Bridgy has a low range on it as well I won't be loosing this.

lakeside53
03-16-2011, 08:32 PM
Do it.. but... with a 3hp motor, your POS bridgy will be a gutless wonder at less than 10hz . Bite bullet and put a 5hp motor on it, direct "in line" with the spindle. Then at 10hz and up to maybe 150hz (if your motor can take it) , you still have about 1hp.

Yes, you can muck around and use the back gear, but....

I run 2hp on a step belt (turned down the shaft on a POS varispeed motor - rated at 3 for less than 20 minutes). It's "ok" for most work, and I could change belts (or wind the varispeed down on my other head), but I usually can't be bothered;)


Oh.. yes.. dump the sheeve and you'll gain about 30%, so maybe 3hp won't be all that bad. The reason BP went from 1 (step belt) to 1.5 (varispeed) was due to the varispeed losses, and due to a lot of customer bitching then 2, followed by a "uprate" of the 2 to 3...

Weston Bye
03-16-2011, 08:32 PM
Are you sure that the vari-drive bushing are OK? My bridgy come to me with a clattering head. Replacing the glue-in plastic bushings made a world of difference. The cost was about $65.

aboard_epsilon
03-16-2011, 08:48 PM
Whats so special about these bushings that you have to buy them ..
cant you make them on the lathe .

all the best.markj

motorworks
03-16-2011, 09:13 PM
John
Did the same with the cnc bridge about 3 years ago.
Tooth belt drive with the slowest at 10 HZ approx 300 rpm
and I left the back /slow gear out and instead I set it up so that
when I put in in back gear It locked the spindle to make tool changes easy...
just a though
eddie

.RC.
03-16-2011, 09:45 PM
Why not use this as an excuse to replace it..

Least then we will be spared the acronym POS Bridgeport... They do well what they were originally designed to do..

Toolguy
03-16-2011, 09:57 PM
John -
I have 2 CNC Milltronics mills with Bridgeport heads and 3 hp motors. They came with VFDs. They have 1 to 1 pulleys with a timing belt. I've been running one for over 10 years with no problems and no maintainence like there is with a variable pulley drive. They are very quiet like a step pulley and with the low range you can go down to nothing on rpm. I have made some pretty heavy cuts with mine over the years and am not lacking for power. The only diff is mine is 60 Hertz, 220 single phase. I would get rid of the sheave drive in a heartbeat. I've run about every manual Bridgeport ever made including 1,2 and 3 head hydraulic trace mills and the main thing I always hated was a clackety variable pulley drive.

philbur
03-17-2011, 05:14 AM
Getting down to the correct speed for slitting saws (without stalling the spindle) can be a challenge with a VFD.

Phil:)

John Stevenson
03-17-2011, 05:49 AM
At 15Hz on the VFD and in back gear it will be doing about 40 to 50 revs which is as low as I go now for the odd boring job so low speed isn't an issue.

I liked Toolguys reply and when I get a chance to pull this, really need a slow day, I'll go along these lines.

Replacing it is not going to happen , much as I hate the damn thing.
Too much work to get it out, at least three big machines to move first but more to the point this machine was about every conceivable extra that I would have to source for it's replacement.

It wasn't bought by choice but was in the right place at the right time.

If I had to buy one today I'd buy the step speed model and fit a VFD, the varispeed only came about as a means of having variable speed.

Timleech
03-17-2011, 06:06 AM
At 15Hz on the VFD and in back gear it will be doing about 40 to 50 revs which is as low as I go now for the odd boring job so low speed isn't an issue.

I liked Toolguys reply and when I get a chance to pull this, really need a slow day, I'll go along these lines.

Replacing it is not going to happen , much as I hate the damn thing.
Too much work to get it out, at least three big machines to move first but more to the point this machine was about every conceivable extra that I would have to source for it's replacement.

It wasn't bought by choice but was in the right place at the right time.

If I had to buy one today I'd buy the step speed model and fit a VFD, the varispeed only came about as a means of having variable speed.

John

I fitted my Elliott mill with a VFD when I first got it, it has a 3 hp motor & stepped pulleys, I don't think I've moved the belt since first setting it up & it does everything I need. OK it doesn't do as much work as your POSB. It is a 2-speed motor and I do use the low speed sometimes, though it's only rated at 2hp on low speed. I'm sure a 5hp motor would be fine if you get the ratio right.

Tim

Weston Bye
03-17-2011, 06:08 AM
Whats so special about these bushings that you have to buy them ..
cant you make them on the lathe .

all the best.markj

They are made of a very hard plastic and less than a hundred thou thick with a somewhat thicker flange. There is also a plastic key that runs in a slot in the shaft. Both of these are glued into place while being sized by temporary precision(?) bushings, the glue and bushings being part of the kit.

I speculate that the plastic, hard as it is, still has a little compliance and lubricity as the sheave rumbles around the shaft. A similar bronze or lesser grade plastic bushing would rapidly deteriorate.

A hokey setup, someday I may contemplate an alternate arrangement, but I just replaced the bushings on my mill recently and it is working well enough.

Peter S
03-17-2011, 06:54 AM
John,

Many years ago I first bought the replacement bushes, but didn't like the look of them (very thin wall, no glue or instructions or internet in those days) and didn't know how to hold them in place. I since found out you can glue them in place with a dummy shaft, or something like that. Anyway, I ended up buying new pulleys from BP, they work like new and are easy to fit, and I still have the old sheaves to repair in the future if required.

Forrest Addy
03-17-2011, 10:08 AM
Work the math. If you elect to gut the variable speed pulley from your Bridgeport and go with a single speed fixed ratio belt drive, choose your ratio carefully. Induction motors are constant torque machines. 3 HP (1500 RPM (motor speed @ 50 Hz) = .9 HP @ 15Hz. Is 0.9 HP a workable figure for you?

If you use carbide cutters to near capacity, I suggest 5 HP picking the lightest motor in the catalog and permanently position a small hoist over the head to aid with tilt and nod adjustments..

Charles P
03-17-2011, 12:33 PM
Well after doing countless literally hundreds of Bridgy motor shaft repairs mine has started making ominous noises as it goes thru the range.

......

If I fit a 1425 rev motor [ standard here for 50 Hz ] and run 1:1 that will give me 3,000 revs at 100 Hz and 430 revs at 15 Hz

Sound OK ?

Yes. Go for it.

I put a proper (modern metric) motor on a step pulley Bridgy and ran it off an inverter. Worked very well.
Rarely needed to change belt positions


http://farm3.static.flickr.com/2322/2364408633_88200c066f.jpg


Charles

John Stevenson
03-17-2011, 02:06 PM
Update:

Did a job at dinner time today it it was really noisy so after the job decided to have a look inside.

Well first thing I found when looking is, it's ugly, I mean dead ugly, Next think is the bushes are toast.

Bad news is I have never seen one of these before, it must be the pre arc model. motor shaft is 24mm with 1/4" key and yes it's a genuine American motor hawk - spit - ding.

Seen 27mm and 28mm shaft models but not a 24mm one.
rang the agents and they just laughed and told me to toss the POS, how did they know it was the POS model ?

Anyway that annoyed me - watch this space.

John Stevenson
03-17-2011, 03:08 PM
Five past seven

FINISHED

Four hours 35 minutes never worked so hard in me life.

Off down the pub, Thursday night, curry night.

Pics at 10:00

jkilroy
03-17-2011, 03:14 PM
I have GOT to get to England so I can go to that darn pub, been hearing about the curry for years now. Oh, and I am very interested in the outcome as I have a loud as hell vari-speed myself and I'd love to quiet it down.

The Artful Bodger
03-17-2011, 04:18 PM
Hmmmmm..... my new turret mill (which I have yet to learn how to use.) has five speeds 240 -2800 rpm. I thought 240 was rather high for a minimum speed when I was buying but...... beggars cant be choosers..:rolleyes:


http://farm6.static.flickr.com/5058/5449940871_e44d4ce286.jpg (http://www.flickr.com/photos/25239206@N06/5449940871/)
Luxcut mill (http://www.flickr.com/photos/25239206@N06/5449940871/) by aardvark_akubra (http://www.flickr.com/people/25239206@N06/), on Flickr

dalee100
03-17-2011, 05:45 PM
Five past seven

FINISHED

Four hours 35 minutes never worked so hard in me life.

Off down the pub, Thursday night, curry night.

Pics at 10:00

Hi,

Why do I feel sorry for your POS Bridgeport? :D In any case, I'll bet it never makes you mad again!

dalee

John Stevenson
03-17-2011, 06:07 PM
Right, back from the pub.

So this dinnertime I had a quick read on how it strips as I have never done one before, seemed straight forward so after the job I was doing pulled it all to pieces with no problems.

The culprits were the bushing on the top of the spindle and the motor, especially the motor.

http://www.stevenson-engineers.co.uk/files/bridgyhead1.jpg

These bushing take out easily, they are not glued in but held in place by the step fitting into an internal groove and the key, all made of Delrin.

Spindle were 35mm bore and 1 1/2" OD.
Motor bushes were 24mm bore and 1" OD so very slim.

The motor key was in two pieces and hardly anything left of the bushes. After ringing for spares and getting insulted, I know it's a POS but it's MY POS !, and also due to the fact that whilst I was stripping this 3 large rotors came in, and all want key-waying I decided to repair this but take measurements for a later fix - if needed.

So lump of Delrin in the lathe, turn to the step OD, turn down to 1" then carefully bore to 24mm and part off. Cut alaong with a pair of sissors and fold up and insert into the motor sheave and try for fit. By a fluke it fitted nicely so made a second.
Fitted a 24mm pilot and broached to 1/4" to clean the bushings up.

Hard bit was making the new key with no milling machine and I couldn't be bothered setting a CNC up so cut a lump out of black Delrin with a hacksaw and filed up to shape and fit.

http://www.stevenson-engineers.co.uk/files/Bridgyhead2.jpg

Motor sheave done.

Repeat for the spindle sheave, same process,clean the shafts up and light lube with some hight temp grease.

Replaced the top spindle bearing and the varispeed thrust bearing as a matter of course. Had a general clean up, put taps down a few holes and wire brushed some threads up to aid assembly.

All went together OK according to the book.

http://www.stevenson-engineers.co.uk/files/bridgyhead4.jpg

Test run before I went down to the pub and it's a different machine, to be honest it has never been so quiet in all the time I have owned it, the bushing must have been on their way out for a long while, so back in business for tomorrow.

And if Messrs Hardinge Ltd of Leicester UK, parts department, are reading this ,

http://4.bp.blogspot.com/_Hg15t-P1a4I/Rp_ksAk-bNI/AAAAAAAAALQ/Re_sLnZf8Rw/s400/8-up-yours.png

aboard_epsilon
03-17-2011, 06:34 PM
Right, back from the pub.

So this dinnertime I had a quick read on how it strips as I have never done one before, seemed straight forward so after the job I was doing pulled it all to pieces with no problems.

The culprits were the bushing on the top of the spindle and the motor, especially the motor.

http://www.stevenson-engineers.co.uk/files/bridgyhead1.jpg

These bushing take out easily, they are not glued in but held in place by the step fitting into an internal groove and the key, all made of Delrin.

Spindle were 35mm bore and 1 1/2" OD.
Motor bushes were 24mm bore and 1" OD so very slim.

The motor key was in two pieces and hardly anything left of the bushes. After ringing for spares and getting insulted, I know it's a POS but it's MY POS !, and also due to the fact that whilst I was stripping this 3 large rotors came in, and all want key-waying I decided to repair this but take measurements for a later fix - if needed.

So lump of Delrin in the lathe, turn to the step OD, turn down to 1" then carefully bore to 24mm and part off. Cut alaong with a pair of sissors and fold up and insert into the motor sheave and try for fit. By a fluke it fitted nicely so made a second.
Fitted a 24mm pilot and broached to 1/4" to clean the bushings up.

Hard bit was making the new key with no milling machine and I couldn't be bothered setting a CNC up so cut a lump out of black Delrin with a hacksaw and filed up to shape and fit.

http://www.stevenson-engineers.co.uk/files/Bridgyhead2.jpg

Motor sheave done.

Repeat for the spindle sheave, same process,clean the shafts up and light lube with some hight temp grease.

Replaced the top spindle bearing and the varispeed thrust bearing as a matter of course. Had a general clean up, put taps down a few holes and wire brushed some threads up to aid assembly.

All went together OK according to the book.

http://www.stevenson-engineers.co.uk/files/bridgyhead4.jpg

Test run before I went down to the pub and it's a different machine, to be honest it has never been so quiet in all the time I have owned it, the bushing must have been on their way out for a long while, so back in business for tomorrow.

And if Messrs Hardinge Ltd of Leicester UK, parts department, are reading this ,

http://4.bp.blogspot.com/_Hg15t-P1a4I/Rp_ksAk-bNI/AAAAAAAAALQ/Re_sLnZf8Rw/s400/8-up-yours.png

Well DONE John .. thats sorted then..
looks easy to make

but never seen anyone showing it being done diy
not anywhere on the net ..
and wondered what all the mystery was ..
as you have prooved John ..there isnt any mystery ..

People who buy the parts must be eather laZy or just too busy ..or loaded with dosh

the same people probably buy the whole quill spring pre-mounted in its housing

all the best.markj

John Stevenson
03-17-2011, 06:45 PM
Mark,
In all fairness there are different designs on these mills.
I have seen the bushes before with the steps in but not as small as this one.
I have also seen then where they are bonded inside a new sheave so you don't have a choice. You have to buy the new sheave.

Out of probably just over 100 motor repairs over the years this is the first motor I have seen with a 24mm shaft. I thought at first it may have been because it was a Adcock and Shipley licensed machine but it still has the big American 9 wire motor on it. It is an old machine though, I believe it's 1969, have to check though, can't remember but the UK made machines have the date in the machine number unlike the American ones where you need to look it up.

DFMiller
03-17-2011, 06:57 PM
Impressive work John,
I enjoyed the pics.
Dave

Toolguy
03-17-2011, 08:28 PM
Bravo John! Great job! :D I've rebuilt several of them. Not that I WANTED to.:mad: It's worth it to make the shop quieter though.;)

Weston Bye
03-17-2011, 09:13 PM
Bravo, John, but Delrin? I thought the bushings to be harder than Delrin. Almost phenolic or Zenite. Well, good work, and let us know how well it lasts. Perhaps the quiet drive will earn your POS Bridgy some new respect. (fat chance)

Toolguy
03-17-2011, 09:17 PM
The OEM ones are made of Delrin or something very similar. The reason they wear out is because they are paper thin. It's a very poor design.

.RC.
03-17-2011, 09:23 PM
damn, and here I was thinking the next pictures we would of it is it in a skip with a nice shiny heavily constructed turret mill in it's place..

aboard_epsilon
03-17-2011, 09:39 PM
Well John ..thats the exact same head i have, well it looks the same..even the same colour ..ready to go on ..its a 30 taper this one ..

all there, bar the top shroud on the motor.

have a stainless steel dog bowl that will take its place .

it's supposed to have had brand new spindle bearings ..and rebuilt through out ..we will have to see if that is the truth.

what did you do ...to be able to turn so thin without collapsing the side with the pressure of the tool.

all the best.markj

doctor demo
03-17-2011, 10:15 PM
Nice job John! BUT... ya could have saved a lot of trouble if ya would have used one of those paper thin steaks they serve at that pub of Yours for bushings, and they would be self lubricating too:D

Steve

John Stevenson
03-18-2011, 05:14 AM
I used Delrin as it was the only material I had to hand and many bushes are made of this. One good thing about Delrin is the bush wears usually without touching the shaft.

I was a bit suprised that the keys were Delrin as all the shafts / sheaves I have see / done in the past had steel keys and plastic bushes but this probably accounts for the wear on the shafts, no wear on these of mine.

However there must be a HP limit one of these keys can take although mine doesn't get any baby sitting.

I had had this argument in the past with thick bushes / thin bushes but the truth is once some wear has taken place to affect the operation of the machine it doen't matter if the bush has another inch of material on it, wear has taken place and needs to be dealt with.

Steve,
They are a bit thicker than the steaks - just - but if we had big massive steaks we would also have to have big trucks with 7 litre engines to haul the end result round and our tiny roads can't take these :D

Sharp HSS is best on this type of material as you need to cut it and not push it.

Anyway it's back into production and earning, 3 biggish rotors to do this morning with 14mm keyways in them.

Circlip
03-18-2011, 06:38 AM
I know it's a POS but it's MY POS !

Oh you big ole softy :o

Pink circle time again.

Regards Ian.

mike4
03-18-2011, 08:59 PM
I used Delrin as it was the only material I had to hand and many bushes are made of this. One good thing about Delrin is the bush wears usually without touching the shaft.

I was a bit suprised that the keys were Delrin as all the shafts / sheaves I have see / done in the past had steel keys and plastic bushes but this probably accounts for the wear on the shafts, no wear on these of mine.

However there must be a HP limit one of these keys can take although mine doesn't get any baby sitting.

I had had this argument in the past with thick bushes / thin bushes but the truth is once some wear has taken place to affect the operation of the machine it doen't matter if the bush has another inch of material on it, wear has taken place and needs to be dealt with.

Steve,
They are a bit thicker than the steaks - just - but if we had big massive steaks we would also have to have big trucks with 7 litre engines to haul the end result round and our tiny roads can't take these :D

Sharp HSS is best on this type of material as you need to cut it and not push it.

Anyway it's back into production and earning, 3 biggish rotors to do this morning with 14mm keyways in them.
Again you have carried out a decent repair ,with a good outcome , your machine is quieter .
I have one question have you notices any change in the finish as I had a mount come loose whe I was doing a long interupted cut which was causing a fair bit of vibration during the first half of the process and there was a slight wavy look to the finish before I got the mount properly tightened.

Michael