Accucraft Isle of Man loco - motor drive shaft/gearbox slippage.

[Bolendo]

Hi folks.

I recently was lucky enough to acquire two Accucraft 2-4-0 type IoM locos. They are robust wee machines, and finished to a very high standard. Most impressive.

However after running happily under test, the motor of one of them started revving without its power being transmitted to the driving wheels. I first assumed that it had stripped its gears. However on closer inspection, the motor drive shaft was found to be turning loosely inside the universal joint that is coupled to the gearbox. I noticed a small aperture in the universal joint casting, and thought that perhaps a grub screw had originally secured the mechanical connection, and had loosened and fallen out.

I used to work in public relations for one of the BR regions, so I am quite used to going down on my hands and knees - so I found myself looking everywhere for this missing grub screw, to no avail.

Then I checked the other loco. It didn't have a grub screw either. The small aperture in the brass casting was there, but its fitting around the drive shaft was tight.

At this stage, I don't particularly want to dismantle the loco, if a simple solution to the problem can be found. I have emailed Accucraft, but I believe they may be on holiday, as I have not heard back from them. They are usually pretty helpful.

I attach some photos. Has anyone had a similar problem?

 

[Greg Elmassian]

It sure looks like there is an allen head setscrew in there.... I have had the same thing happen on one of my Accucraft locos and there was no flat ground into the shaft...

can you get closer / better resolution?

Greg

 

[dunnyrail]

Hi folks.

I recently was lucky enough to acquire two Accucraft 2-4-0 type IoM locos. They are robust wee machines, and finished to a very high standard. Most impressive.

However after running happily under test, the motor of one of them started revving without its power being transmitted to the driving wheels. I first assumed that it had stripped its gears. However on closer inspection, the motor drive shaft was found to be turning loosely inside the universal joint that is coupled to the gearbox. I noticed a small aperture in the universal joint casting, and thought that perhaps a grub screw had originally secured the mechanical connection, and had loosened and fallen out.

I used to work in public relations for one of the BR regions, so I am quite used to going down on my hands and knees - so I found myself looking everywhere for this missing grub screw, to no avail.

Then I checked the other loco. It didn't have a grub screw either. The small aperture in the brass casting was there, but its fitting around the drive shaft was tight.

At this stage, I don't particularly want to dismantle the loco, if a simple solution to the problem can be found. I have emailed Accucraft, but I believe they may be on holiday, as I have not heard back from them. They are usually pretty helpful.

I attach some photos. Has anyone had a similar problem?

Not sure what size grub screw is likely to be but will be small. Not even sure if they will be imperial or metric but I quickly found this. If you can ID metric or imperial there may be a similar set for imperial (ba sizes).

Sealey Grub Screw Assortment 250PC M4-M10 DIN 916 | at Zoro

Sealey - Grub Screw Assortment 250PC M4-M10 DIN 916 Metric available at Zoro.co.uk - UK's Leading Supplier of DIY Tools and Supplies'

www.zoro.co.uk

 

[Greg Elmassian]

1.5mm are the sizes of the setscrews (grub screws) on the universal I have... I note it on "Tips" on my K4 Pacific

K4 Disassembly

Greg Elmassian web site on large scale trains and garden railroads, cigars, and computers

elmassian.com

Greg

 

[Bolendo]

1.5mm are the sizes of the setscrews (grub screws) on the universal I have... I note it on "Tips" on my K4 Pacific

K4 Disassembly

Greg Elmassian web site on large scale trains and garden railroads, cigars, and computers

elmassian.com

Greg

Hi Greg. Thanks for that information. I looked at your article - it was a most interesting read. I have a macro lens for my camera (if I can find it) and will try and get some better photos.

Bob.

 

[Bolendo]

Not sure what size grub screw is likely to be but will be small. Not even sure if they will be imperial or metric but I quickly found this. If you can ID metric or imperial there may be a similar set for imperial (ba sizes).

Sealey Grub Screw Assortment 250PC M4-M10 DIN 916 | at Zoro

Sealey - Grub Screw Assortment 250PC M4-M10 DIN 916 Metric available at Zoro.co.uk - UK's Leading Supplier of DIY Tools and Supplies'

www.zoro.co.uk

Thanks for that. Greg has indentified that they are most probably 1.5 mm screws, so hopefully I can get some from the supplier that you recommended. I will keep you posted. Cheers. Bob.

 

[Greg Elmassian]

It's a grub screw that uses a 1.5 mm driver... don't know the diameter and thread pitch.

Greg

 

[Paul M]

Make sure you use the correct metric/ imperial Allen key, if the key is slightly loose, its easy to mess up the screw head, and there's no way of getting them out

 

[Greg Elmassian]

Accucraft often uses unusual hex driver sizes, had to buy a set of Wiha drivers to handle them.

Greg

 

[dunnyrail]

Thanks for that. Greg has indentified that they are most probably 1.5 mm screws, so hopefully I can get some from the supplier that you recommended. I will keep you posted. Cheers. Bob.

It may be worth your while trying to speak to the supplier, id your problem and get one or two differing sizes around that. I am not ever sure how these small things are measured in size be it thread width or whatever. You will certainly find that the allen key is a very small tricky to get so may be worth getting the right ones as well. Likely you will end up with something that you do not need but only way to be fully sure if Accucraft do not come up with the goods. Sadly I do not have any Accy locs to try experiments on sizes for you.

 

[Paul M]

I bought one of these sets from a well know Internet source, it seems to cover most eventualities on my Accucraft locos. But be careful to use the right size, an imperial key will fit a metric screw but may be loose, which means you may round off the hex inside the screw, then you really are sc*w*d

 

[tac foley]

Accucraft threads nuts bolts and screws are ALL metric.

 

[Greg Elmassian]

I need to check that loco, I said 1.5mm, but that seems large. In any case, I really think your grub screw is still in there... did you look at both ends of the coupling? Hard to believe both could be missing. As I stated, mine came loose, on both my K4's (I have 2)

Greg

 

[Bolendo]

Success!!! Thanks for all your help. I found my macro lens, and took some more accurate photos. I attach them below. Greg was right - the grub screw is still in there. It had just worked loose. By chance, I had an Allen key that looked like it might be the right size. It was for tightening rail joiner screws. As it was a German product, I assumed it to be metric. However it had a slight rounded lobe on the end, which didn't allow a tight fit into the screw hex aperture. In desperation, I got some wire cutters and got a clean cut through it, exposing the hex shaft. A lucky break indeed. It slipped into the aperture snugly, and I was able to tighten the screw down onto the shaft. I turned the wheels and could see the motor shaft revolving. In pitch darkness, I took the loco outside and tested it. When physically stopped by a finger, the wheels spin, so I guess it is as tight as it can get. Once again, thanks for all your help and references to keys, screws etc.

 

[Greg Elmassian]

Next time you have to work on it, you need to grind a small flat on BOTH shafts, and then locate the grub screw on it. It WILL loosen again.

Greg

 

[Bolendo]

Next time you have to work on it, you need to grind a small flat on BOTH shafts, and then locate the grub screw on it. It WILL loosen again.

Greg

Sounds like good advice. I will do as you suggest. Thanks again.

 

[Greg Elmassian]

It's a minor design flaw... you can grind a flat with a small dremel grindstone, unfortunately, you will want to unbolt the motor, and then you can clear the universal. Mark where the body of the universal reaches on each shaft with some tape. when you disconnect it, then it is easy to see how far from the end of each shaft you should grind a flat. It does not take much, maybe 1/4 or less of the diameter.

Of course as you retighten, you need to "feel" the location of the flat.

Trying to tighten enough that it won't slip will normally strip the threads or the hex recess on the grub screw.

Greg

 

[dunnyrail]

Success!!! Thanks for all your help. I found my macro lens, and took some more accurate photos. I attach them below. Greg was right - the grub screw is still in there. It had just worked loose. By chance, I had an Allen key that looked like it might be the right size. It was for tightening rail joiner screws. As it was a German product, I assumed it to be metric. However it had a slight rounded lobe on the end, which didn't allow a tight fit into the screw hex aperture. In desperation, I got some wire cutters and got a clean cut through it, exposing the hex shaft. A lucky break indeed. It slipped into the aperture snugly, and I was able to tighten the screw down onto the shaft. I turned the wheels and could see the motor shaft revolving. In pitch darkness, I took the loco outside and tested it. When physically stopped by a finger, the wheels spin, so I guess it is as tight as it can get. Once again, thanks for all your help and references to keys, screws etc.

Happy result.