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Model Forum / General / Models / April 2009Fobco Star Advice (Long)
Hi all, I have acquired (for free!) a Fobco Star benchtop drill. Not sure how old it is, but it looks like it has seen some use. A little rough around the edges, but in good order mechanically. It is fitted with a Brook 'Gryphon' (sp?) motor, in which the bearings sound like they have seen better days and are squeaking under load. I am thinking of replacing the motor and fitting an inverter for better control of the speed. The problem I am having is trying to remove the motor pulley to get the old motor out. Here are the steps taken so far:- 1). Grub screw removed, tried carefully levering pulley off. No joy. 2). Sprayed some penetrating oil in the top and through the grub screw hole. Left to soak overnight. Tried levering again - nothing. 3). Heated pulley up with hot air gun to approx 100 deg C - still no movement. 4). Dug out the three leg puller (I know the pulley is cast iron, so am going very gently so as not to break lumps off the pulley). Put as much pressure on the pulley as I dare, with more heat and oil. Still no movement. Puller will be left on overnight, under tension, to see if something will move. Can anybody suggest the next course of action? As I see it, options are to cut the pulley off the motor shaft, then machine the pulley to remove the remains of the old shaft. Not a big deal as the motor is being replaced. The new motor has a 14mm shaft, whereas the original motor, as far as I can measure it, has a 16mm shaft. This means some work on the pulley is necessary anyway to make an bushing to fit the new motor. Any advice appreciated. Anthony Remove colour from the SKY to reply > Hi all, > [quoted text clipped - 34 lines] > > Have you checked that there is not another grub screw in the hole still. On more than one occasion I have encountered pulleys held on with 2 grub screws, one locking the shaft and the other locking that one. >> >Have you checked that there is not another grub screw in the hole still. >On more than one occasion I have encountered pulleys held on with 2 grub >screws, one locking the shaft and the other locking that one. Once having checked that... another option is more heat. If it's an Iron pulley, you can get it a lot hotter than 100°C Make adapter that fits the pulley grooves to spread the load, and use a bigger puller. Adapter would be a bit of heavyish plate, cut hole in the plate to size of a pulley groove, probably the 2nd or 3rd one. divide plat in half, so you have 2 half-holes. put around pulley, then fix halves back together with additonal plates and bolts. Apply puller.  SignatureAustin Shackles. www.ddol-las.net my opinions are just that Travel The Galaxy! Meet Fascinating Life Forms... ------------------------------------------------\ >> http://www.schlockmercenary.com/ << \ ...and Kill them. a webcartoon by Howard Tayler; I like it, maybe you will too! . -- jasonballam Any chance its threaded onto the shaft and the grub screw just stops i coming loose. Shaft is likely to be 5/8" not 16mm and its Brooke Crompton Jaso -- jasonballam > Shaft is likely to be 5/8" not 16mm and its Brooke Crompton > > Jason It`s Brook Motors and the model is a Gryphon.Brook amalgamated with Crompton Parkinson long after that drill was made.I Brook has changed it`s name several times over the last thirty years. >Hi all, > [quoted text clipped - 20 lines] >movement. Puller will be left on overnight, under tension, to see if >something will move. You could try putting the pulley under tension with the puller and hitting the bolt in the centre of the puller with a large hammer, while suitably supporting the motor shaft on a solid bench/foor. I've found that this can sometimes start the movement which can then be followed by use of the puller in a more conventional fashion. It is all too easy to accidentally go too far with the tension on the three legged puller and break out a chunk from the pulley, at which point you find that replacement pulleys are expensive! There is an earlier thread in this newsgroup entitled "Safe removal of aluminium pulleys with key" where various people gave me some excellent advice for a similar operation on a Meddings drill which was carried out successfully. Alan > Hi all, > [quoted text clipped - 32 lines] > Anthony > Remove colour from the SKY to reply Check there aren't 2 grub screws in the hole(s); this happened to me, it took a big press to remove (read destroy) the 5 step pulley from the quill on my drill, we found the 2nd set of grubscrews once it was in pieces. Martin Signaturemartin<dot here>whybrow<at here>ntlworld<dot here>com > Hi all, > [quoted text clipped - 32 lines] > Anthony > Remove colour from the SKY to reply As others have suggested check for a second grub screw either in the same hole or at 90deg to the first one. While the puller is under tension give the center screw of the puller an sharp rap with a hammer ,some times it just takes a bit of a jarring to start the pulley on it's journey . You could also drill and tap two holes in the pulley face and use two bolts and a cross bar puller rather than a claw leg puller . Leg pullers are notorius for breaking pieces out of cast pulleys. BTW If using heat you need to heat the pulley fairly fast so the shaft dosen't heat up with the pulley .I would think a heat gun wouuld be fairly slow heating and the heat would be getting to the shaft as well. SignatureKevin (Bluey) "I'm not young enough to know everything." bluey69@west.net.com.au > Hi all, > [quoted text clipped - 32 lines] > Anthony > Remove colour from the SKY to reply In addition to the other good advice you have been given, I have 4 suggestions. First, try driving the pully further onto the shaft, using a hollow driver. Second, if you have room, fabricate a thick steel plate to go behind the pulley to take and spread the force. Third, use a straight bolt type puller which you can fabricate if you do not have one. Fourth, if all else fails saw off and drill out the motor shaft (sacrifice the proper part). Don Young (USA) > The problem I am having is trying to remove the motor pulley ... Mine (had it from new) had the same motor until it gave up. The pulley can be a bit if a bugger to move. If tensioning a puller and hitting the end of the jack screw does not work, try tapping the pulley repeatedly, both radially and axially (continuously for perhaps several minutes) but not hard, all round the rim of the pulley with a hammer. This technique is often effective in breaking a stubborn joint. The big wallop tries to break the hold all in one go. I think the tapping technique uses the elasticity of the parts to seek out a tiny areas of the joint surface that can be made to give a tiny bit. SignatureCharles Lamont >> The problem I am having is trying to remove the motor pulley ... > [quoted text clipped - 7 lines] > technique uses the elasticity of the parts to seek out a tiny areas of > the joint surface that can be made to give a tiny bit. Thank you everybody for your replies so far. I now have my propane torch back, so I can apply a bit more heat to the puley, as well as using Charles' 'tapping' method to hopefully free off the pulley. There is definitely only one grub screw present, as you can see the shaft through the hole when you remove it. No screws at any other location on the pulley either. If I have no luck with more heat, I think I will go with the original plan of cutting the motor shaft and machining the remains out of the pulley. Is the motor shaft likely to be hardened at all? Anthony Remove colour from the SKY to reply. >>> The problem I am having is trying to remove the motor pulley ... >> [quoted text clipped - 23 lines] > Anthony > Remove colour from the SKY to reply. I have cut quite a few motor shafts and have never found one to be hardened. If you have access to a press it should make short work of removing the shaft stub from the pulley. If you drill, note that you do not have to drill all of the shaft out of the pulley. You can run an undersized drill only thru the pulley depth, leaving a moderately thin shell and a blind hole. A drift in the blind hole hit with a hammer will pull the shell right out with no damage to the pulley bore. Don Young (USA) >>> The problem I am having is trying to remove the motor pulley ... >> [quoted text clipped - 9 lines] > >Thank you everybody for your replies so far. [cut] >Is the motor shaft likely to be hardened at all? I have a single phase Gryphon motor here from a small bench drill and the motor shaft turned very easily with an ordinary HSS tool so I think the answer is likely to be no. A Newman motor on the other hand had a moderately hard shaft but it turned easily with a carbide tipped tool. Alan > Hi all, > > I have acquired (for free!) a Fobco Star benchtop drill. Not sure how old > it is, but it looks like it has seen some use. A little rough around the > edges, but in good order mechanically. <snip> Well, the pulley is now off the motor. It came off much easier than I expected. Charles' advice about tapping gently around the pulley to break any corrosion certainly did the trick - some gentle pressure with the puller had the pulley on its way. Thanks to everyone who took the time to reply. Anthony Remove colour from the SKY to reply |
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