From a production viewpoint line boring seems an excessive faff as compared to simply making things accurate in the first place. To line bore the motor case needs to be assembled empty, bored, marked for re-assembly in the correct orientation, then disassembled so the motor can be built up. Sounds an unlikely business especially if the boring were done, as it should be, before the electrics were installed.

I've had a couple or three plain bearing motors apart and never made any attempt to keep the front plate in its original orientation and had no running or bearing issues. I could have been lucky but I doubt it. Back plate with the connections naturally has to go in the right way.

I don't know how accurately the end castings were made in the first place but it seems more likely that the snug fitting recess into which the main body slots would have been machined first and the bearing shell bored concentric to that. If you are going to bore a plain bearing to size after fitting "close" will be perfectly adequate for the original hole whilst the extra effort and expense of "dead nuts" would be a complete waste of production line time. All depends on production set-up and machining sequence.

Clive

Edited By Clive Foster on 03/09/2014 17:29:44

Hi there, CotswoldPhil,

Oilite bearings are sintered bronze – the sintering gives them a porous structure which is (ideally) vacuum filled with oil.

The makers' 'how to' literature, as far as I can remember, said that reaming to size after assembly is a no-no because the reamer 'smears' the bronze, closing up the pores and impeding, if not totally preventing, the oil reaching the bore. Presumably, the same no-no applies to boring?

The specified fitting method is to insert using a stepped mandrel whose section in the bush has the right diameter to control the finished bore.

Best regards,

Swarf, Mostly!

The bearings are Vandervell, not Vanwall, and they are still in business. although I am sure it is a long time since they made that type of bearing, you could ask them. Have you tried the new bearing in position and then rotated the motor end cap to see if the rotor frees off. Are the end caps pressed metal or cast, and what type of flange is there where the end cap meets the stator housing?They should align without any reaming, but it is possible that the end cap is distorted or the flange is damaged. I can remember that we used to bump the end caps with a rubber mallet whilst the through bolts were loose to line everything up. Is the binding in the bearing, or is it the squirrel cage touching the stator? I uset to service a lot of this type of Crompac motor which was fitted to all sorts of small industrial machinery. can you post some pics?

Phil

East Yorks.

Vandervell steel backed white metal bearings are ready to fit in automotive applications, the instructions warn against scraping. I would have thought that if they can make shells that accurately, a split bush for a motor would need no further work after installing. The only precision tasks required would be the hole size and concentricity with the register. My vote goes for them being presized to give the correct clearance after fitting in a correctly toleranced hole. Your new bush may have closed up on being pressed in. Many bearings rely on the fit in the housing to bring them to their designed fit, even ball races can be ruined by too small a housing or too tight on shaft, Torrington needle rollers certainly need a tightly toleranced hole and shaft to achieve the correct running fit.

Mike

Edited By Michael Poole on 03/09/2014 20:42:14

Hi Phil,

Would the eccentricity be due to wear? With the bearing installed in the housing is the hole round? A pair of internal calipers will easily detect an out of round condition. If the shaft is oiled this can flatter how good the fit is.

Mike

I,m pretty sure its a misalignment problem. These motors are turned out like shelling peas, they were cheap and cheerful. The stators are wound and the rotors are just popped in. When dismantling any motor its is important to mark the stator and end cover so that correct alignment is established, otherwise binding takes place.(Two parallel scriber scratch marks one end, stator to end cover, and single scratch mark stator to end cover the other end) I suggest you slacken off all 4 bolt and rotate the rotor by hand and tighten 2 bolts diagonally a bit at time. You may find that a tap here and there with a soft mallet will move things so that the rotor moves freely.Ted

White metal bearings are made by passing a broach through them, possibly gang broached in one go. I think the broach was not drawn back through the bearings. Split bearing were placed in a housing which matched the finished size before broaching. Some of them were heavily copper plated before the white metal lay. This may explain why the hole is off center. I very much doubt it was done in the motor with both ends attached as that is too much work. I have always admired the excellent surface finish on white metal bearings.

Clive