Member postings for Graham Mcconnell

Hi Len, Please send me an email to "[email protected]" and I'll reply with the schematics I have. If anyone else wants them please feel free to email also.

All the best

Graham

Hi,

I have recently converted mine to Linux cnc. I choose to ditch the stepper drivers as they are based on old technology and can suffer resonance at certain speeds and lack speed and acceleration compared to modern drives. I also upgraded the X an Z to use slightly larger motors, on mine they were nema 23 size. For drives I initially used the cheap ebay "TB6600" ones at 48v but they blew up. They were advertised as working to 48v at the time (They are not now, I wonder why!), so I swapped to "Gekko G201x", these have been perfectly reliable.

TBH the stepper motors were the least of my problems. By far was the spindle motor drive, It needs a 0-10v speed signal. Again I turned to ebay and got a breakout board that provides it, however the spindle speed was not very controllable and it hunted. All the ebay boards I could find used PWM and a capacitor to provide the signal. I tried various boards and homemade solutions but none really worked. In the end I got Linux CNC to output an 8 bit speed signal on a second parallel port then used a digital to analogue converter to feed that to the drive, both the electronics and software programming were very much non trivial! I be very curious to know what others have done and how they perform.

One big thing, if you are using the original spindle drive "GEC Gemini", please please please replace the "Rifa x2" capacitors on the board with suitable modern replacements if you haven't done so already. These will be at the end of there lifetime and the body will almost certainly be cracked. They can and do explode and catch fire if left. Please view the following youtube video for more detail:

https://www.youtube.com/watch?v=XAbrU17hLTM

I have a wiring diagram for lathe and a home made schematic of the spindle drive if that's of any help, I've also found a picture of my drive before I changed the caps, so I circled the caps that need changing. You can just about see the cases are cracked in the photo.

Graham

Edited By Graham Mcconnell on 05/04/2020 14:51:55

Mine has a graduated wheel, but it's left of the photo, you can just see the knurling. I guess you have the normal version with the power drive on the right hand side? which I'm guessing is what that dog gear engages. On mine the power drive is attached to the left of the table with a lever on the front that engages the power feed. Hence the difference in design. The spring and nut are not critical and anything that fits should work. The 1/4 set screw and pad is to just lock the nut on the threads, you can see it in my photo.

All the best

Graham

Hi John,The nut on my machine is 1 1/2" outside diameter and 1/2" thick, with the outside knurled. There is also a 1/4" set screw with a brass pad on one side. It's threaded 3/4" UNC, so looks to be slightly different to yours. The spring is on the left inside the dog clutch on mine with the nut bearing up against the right hand side of the handle. I've included a photo.

That serial puts yours as mid 1973. mines a late 77.

All the best

Graham

Ah, I've been looking at my manual in closer detail and I assume there are actually different versions / revisions of this mill and not just the "normal" vs "universal" types. Mine is a late model universal and according to the manual I have the hand wheel is permanently engaged and secured by 2 knurled lock nuts. However it isn't, and has a knurled nut that can be unscrewed to disengage the hand wheel, much similar in construction to the normal version. I also assume this why the part numbers don't match. The nut I think your after is listed as MH1-4-42 in my manual (83 on diagram). I shall measure it tomorrow and report back. But just in case please don't assume that these parts will fit yours.

All the best

Graham.

Correction, I read the calipers wrong, it's 1/16" wire diameter!

Sorry.

Graham

I can't find a reference to the nut in my manual, but I may just being blind! There are no odd nuts on my machine so would just assume that it's a standard nylock. The spring is located in the table feed handle and is 1" in outside diameter, 1/8" diameter wire, 7/8" in height with 5 coils. I attached a picture of it.

Hope that helps,

All the best

Graham

Many thanks everyone. I'm almost certainly going to end up making these gears myself, using a single point tool, but unfortunately it will have to wait for a while. I do have a milling machine but it's of the mini variety. I'm sure it would cut the gear but not to any consistency and that would lead to the drive destroying itself. I think a new addition to workshop is in order.

When I posted the original question I was rather hoping I'd missed something obvious and I could get an off the shelf item.

Once again thanks everyone, especially John for the CAD work! I shall post an update on the outcome.

Sorry forgot the pictures...

Many thanks for the replies so far. I have had a quick look at some of the web pages suggested, very helpfull, but I think I need a more in depth look with a a bit of digest time. The drive has a sticker stating "Oildrive Modena" on it so I assume it's Italian of mid nineties vintage, and as the gear is 12mm thick I rather suspect it's metric, all the bolts are.

I have attached a picture of the gear, I don't have a flatbed scanner so I printed a 1mm grid and placed it around it. I've also attached a picture of the drive to show where they go.

I take it that I'm unlikely to be able buy a straight replacement? Is this something that I can get made? Laser cut? Small specialist gear manufacturer? A new drive would be over £1000 so I would really like to get this working.

As to why they are missing, I suspect that the drive actually has another fault somewhere and these gears were removed to allow the track to roll, why they then didn't stash them away on the machine somewhere I don't know! I also haven't tested it because it's pointless unless I can get these gears, and the engine needs a few bits sorting, it hasn't run for 6 months.

Many thanks

Hi. This is my first post so I hope it's in the right category!

I'm trying to rebuild a mini digger and 1 of the track drives is missing a few gears. I've searched for the digger manufacturer (CME) and the drive manufacturer (Oildrive) with absolutely no luck, so my only options seems to be, buy a gear and machine the bore to suit or make the gear, which I'd perfer not to do as it probably needs to be hardened in some way.

The gears are on the final stage reduction and it's missing the 3 planet gears. I've took the other drive apart and measured the gear, and I got a overall diameter of 62.8mm with 25 teeth, it's also 12mm thick. Plugging these numbers into some online gear calculators seem to suggest a mod number of 2.37?

I have a copy of Ivan law's "Gear and gear cutting" and now I'm even more lost! I seem to require the "PCD" dimension but I've no idea how to measure that. The sun gear is also very worn , so I'm unsure about taking any measurements off that. Any advise you could give would be greatly appreciated.

Many thanks

Graham