Colchester student 2500/harrison m300 feed gearbox cams

[damianParticipant @damiannoble34800]

Hi all,

Posting here for a bit of help as a search of the internet hasn't turned up what I'm looking for.

When I got my Colchester student 2500(metric 6mm leadscrew) the gearbox was seized which is the same as the M300 problems. I stripped out the four cams carefully numbering them up after a clean with solvent to remove the old oil and residue.

Unfortunately I didn't get back around to reassembling the gearbox until last weekend after a gap of 5 months the solvent which was left on the parts had dissolved my permanent marker and now I'm guessing which gear is supposed to make in each of the 8 positions on the rotary knob?

Looking from the back with the lead and feedscrew to the left and cam 1 to cam 4 follower left to right. I have the 8 gears (again left to right) meshing in with the selector knob position as follows 1-2-7-8-3-4-5-6. Would like to confirm this is correct?

The selection was vague and taken me some rotating about with the selector to make the gears line up in each of the detent positions.

I have tried the harrison m300 Yahoo group but it is very quiet on there.

Many thanks for the info and help in advance guys

Damian

[damianParticipant @damiannoble34800]

Cam orientation

[FMESParticipant @fmes]

Ahh, the benefits of hindsight and photos..

Is this any good? **LINK**

Regards

[damianParticipant @damiannoble34800]

Posted by FMES on 27/03/2019 20:48:31:

Ahh, the benefits of hindsight and photos..

Is this any good? **LINK**

 

Regards

Agreed and lesson in not trusting 'permanent ' marker again. Scribed line across the delrin cams will be the way to go.

Seen the link above but the photo's and videos on the gearbox don't show the cam as it's hid behind the selector forks and also they dont mention how they relate to each other.

I have seen one video on you tube that states selection 1 has the first gear made. No further details.

I'm looking at a last resort of a mail to the 600 group to get some detail.

Edited By damian noble on 27/03/2019 21:03:20

[BazyleParticipant @bazyle]

Are you on the Harrison Yahoo group?

I analysed the gearbox a few years ago while considering making one for another lathe. I'm struggling to understand my spreadsheet but here goes.

Edit – photo is from back so reverse my left right below.

From the input side the selector blocks (the blocks in the photo) go in the order, wrt the dial numbers:
(4,3,) (6,5,) (2,1,) (8,7) with any block not in play in the middle neutral position.
Another description is the left block moves to the left in position 4, to the right in position 3 otherwise in middle neutral.

therefore
position 1 meshes 33 to 24
position 2 meshes 33 to 27

position 3 meshes 22 to 20
position 4 meshes 22 to 22

position 5 meshes 22 to 23
position 6 meshes 22 to 24

position 7 meshes 22 to 26
position 8 meshes 22 to 28

Edited By Bazyle on 27/03/2019 23:00:21

[damianParticipant @damiannoble34800]

Posted by Bazyle on 27/03/2019 22:54:41:

Are you on the Harrison Yahoo group?

I analysed the gearbox a few years ago while considering making one for another lathe. I'm struggling to understand my spreadsheet but here goes.

Edit – photo is from back so reverse my left right below.

From the input side the selector blocks (the blocks in the photo) go in the order, wrt the dial numbers:
(4,3,) (6,5,) (2,1,) (8,7) with any block not in play in the middle neutral position.
Another description is the left block moves to the left in position 4, to the right in position 3 otherwise in middle neutral.

therefore
position 1 meshes 33 to 24
position 2 meshes 33 to 27

position 3 meshes 22 to 20
position 4 meshes 22 to 22

position 5 meshes 22 to 23
position 6 meshes 22 to 24

position 7 meshes 22 to 26
position 8 meshes 22 to 28

Edited By Bazyle on 27/03/2019 23:00:21

Hi Bazyle

I will have to check against the above if I get what you mean.

Yes I'm on the yahoo group but finding anything with the search function is hit and miss I find.

Damian

[RobCoxParticipant @robcox]

Hi Damian,

I took my M300 gearbox off a couple of years ago when I gave the whole lathe a clean up and fixed broken/worn out bits. I took a lot of photos of the gearbox at the time in each of the selector positions.

I'll try and dig out the photos tonight and post them in an album. They may help you deduce which cam goes where.

Regards

Rob

[damianParticipant @damiannoble34800]

Posted by RobCox on 28/03/2019 08:31:54:

Hi Damian,

I took my M300 gearbox off a couple of years ago when I gave the whole lathe a clean up and fixed broken/worn out bits. I took a lot of photos of the gearbox at the time in each of the selector positions.

I'll try and dig out the photos tonight and post them in an album. They may help you deduce which cam goes where.

Regards

Rob

Many thanks Rob I can work with the info above but pics tell a thousand words.

Once I get it back together I will take a few pics and post them.to the harrison group.

Incidentally I've had to replace the powerfeed output shaft and bush (harrison manual 303056 and 303107 colchester numbers are different) as these were badly worn, luckily a friend turned these up for me. Not sure about the other phosphor bronze bushes in the box but probably some wear in those too.

Cheers all for the assistance

[damianParticipant @damiannoble34800]

Using the info above from Bazyle I have refitted the cam assembly and adjusted the selector knob so that it changes whilst lining up the gears fully. Had to file the flat slightly on the selector

The selector still needs the occasional jiggle but changes are a lot lighter and more positive.

As Bazyle said looking from the rear as most photos of the removed box are, the numbers are reversed from the input side.

So the positions on the selector are (7,8)(1,2)(5,6)(3,4)

Cheers

Damian

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