Simplex Gremlins Strike Again

I completed my Simplex three years ago and I've had it in steam for well over 100 hours in that time and its run very well.

I decided to give it a good check over and clean the clack,injectors etc ready for the running season when the weather improves.

And I found that one of the rear axle boxes had excessive wear, all the other axle boxes showed no sign of wear.

As the ash pan sits over the top of this axle I thought that ash was getting onto the axle, but I have a brass guard over the axle that on inspection seems to be doing its job.

All the bearings get a good oiling before I run so I don't think its lack of oil and the oil ways were clear.

A friend said that he had seen this before on a 7 1/4" loco and suggested that it may be due to uneven axle loading from the springing, resulting in a lot of the weight being carried by that one axle causing it to run hot and wear. When I stripped it down I did find that one of the spring hangers had come lose which supports this suggestion.

Has any one else come across this or has any other ideas as to its cause.

Stew

Out of curiosity, had you noticed any deterioration in performance?

Neil

WOW, just a 100 hours use - makes you think. I wonder how much better they would have been with bronze bushes?

Nope:- she was running like a little sewing machine.

Stew

Well over 100 hours I don't log my running time so it could be approach 200

The axle doesn't show too much sign of wear , which tends to tell me 'it' is the surface which is softer and holding the abrasive (ash) ?

Amazing! I hope you discover what has caused this. It actually looks like it was machined oval!

I have a Super Simplex and when I get the locomotive home after running it, I usually turn it upside down on my construction stand to inspect things underneath. I hope I would notice something unusual before things got too out of order.

Keep us posted.

David

The axle journal on that side has worn down 0.4mm the other side has negligible wear.

Hi David

I roll mine on its side after each run unfortunately its been the same side, the effected bearing always ended up on top so the bearing wasn't that visible and I missed it, I did notice the spring hanger was coming lose and just kept tightening it up, but it never occurred to me that it would cause the bearing to wear.

I've got material to make a new axle and boxes, but I'm thinking about boring out the boxes and inserting an Oilite bearings with a new axle.

Stew

It looks like an alignment issue, where the crank pins, or coupling rods have been pulling the axle on one side to form the oval wear pattern. Ive had similar in the past where the forces on an axle were pullung down on one side, meaning the axle bearing the opposite side wanted to lift, over time it wears the bearing.

If the wheels were correctly quartered then I'd say it was the coupling rods, wheels, or crank pins that are at fault, and they should be inspected next to make sure there' no wear on them of the same.

I may be wrong, but I've seen it happen before, and now means I have to replace some bronze bearings myself.

If the wear on the axle box was due to connecting rods or crank pins, it seems like the wear would be forward and aft as the axle box was pulled and pushed.

But, since it looks like the wear is in the up and down direction, one would think it was due to some fault in the suspension.

Stewart, I have oilite bushings in my axle boxes. It's not yet clear if I should have used bronze. In any case, I machined my axle boxes using an angle fixture bolted to a face plate in the lathe. Each axle block was clamped into the angle fixture and machined in the exact orientation that that each would be in the locomotive.

Using this type of a fixture, you could bolt up the axle block, of the pair, that has very little wear and dial it in to adjust the angle fixture. Then put the poorly worn one in, and re-bore it for bushings. Otherwise, the worn axle box leaves you very little for a reference to rebore it.

I did this for all of my axle boxes from the start and they turned out perfectly. Attached should be a photo of one of the boxes being bored and a photo with a test axle going through the bushed axle box and through the axle box on the other side.

David

Edited By David Wasson on 03/03/2018 00:34:12

Could be just a soft bit of material? Quality does seem to vary greatly on smaller section materials used for models.

Thanks for your input and discussion Gents

I'm coming round to the opinion of David that the wear was caused by uneven axle loading, as I've eliminated crank pin and rod alignment issues.

I have material to make new axle boxes and axles but I'm contemplating bushing out the axles with either a phosphor bronze or oilite bearing as this would save a lot of time, I can use the unworn box with stops to help set up the worn box and use a boring head in the mill to open it out, I'd do the unworn one as well so both are the same.

I use a slightly different approach to making axle boxes to David but both methods ensure that the critical feature of ensuring both boxes are aligned identical with the bore in the centre.

Using the four jaw I bore the boxes and finish off with a reamer.

Then I turn up a mandrel a close fit on the bore, I then centre this mandrel true in the spin indexer

Mount the axle box on the mandrel then mill the groove for the horn box taking the same amount of each side, so when the axle will be exactly in the centre of the horn.

To quarter the wheels I use my home made quartering jig.

Stew

Hi Stewart,

Looks like you have a perfect way of making new boxes and retaining the reference to where the center was. I sense you understand the importance of this. I assume you are making a complete new one as the old one is worn to the extent that it cannot be bored and rebushed? I'm sure you have considered that and are going with a new axle box. Such a pain to make a complete new one, or, pair.

The hope for my loco is, as wear starts to show up in the axle box bushings, they can be replaced before anything gets too bad. If you bush yours, you will have that option also.

Nice photos. I have used nylock nuts on the spring studs, maybe something to consider for yours?

I have noticed, on my Super Simplex that the front end is much heavier than the back. I have had to put stronger suspension springs in the front, medium in the center, and lighter in the back. For me, this was the only way I could get it to sit level! Also, with nylock nuts, you can individually adjust the tension on the springs, and be sure they will not loosen.

David

Edited By David Wasson on 03/03/2018 13:53:19

Just to keep you updated on this.

I've repaired the worn bearing by pressing in a oilite bearing I did both journals just to keep that axle the same.

This is how.

First made a new axle.

Then centred the mill on the unworn axle block using a co-axle clock.

Zeroed the DRO and locked the slides and with a vice stop

Bored out the worn axle box.

Then bored the unworn bearing out.

The Oilite bearing were over size on the OD so made an expandable mandrel.

Turned the bearing down for a tight fit in the axle box

Pressed the bearing in with a spot of Loctite for good measure

Job Done

Stew

Edited By Stewart Hart on 26/03/2018 08:53:34

Hi Stewart,

Looks great! Sorry you had to make a new axle. Were there quartered key ways in the axle? Was it damaged by the worn axle block?

Also, out of curiosity, was the "good" axle block discovered to be fairly round when you clocked it in?

Will you do anything different in an attempt to prevent this from happening again? I have a Super Simplex and am wondering if there is anything I might do to prevent this.

David

All this begs a couple of questions. What is the track like that you run on and have any other club members had similar problems. With simple bearings like these, both axle boxes must move up and down at the same rate, however the track will have small deviations from side to side. Others have said that the front end of SIMPLEX is heavier than the rear end, so in effect the rear axle boxes have to play 'hop scotch' as they travel over the track. David W identified this as a problem and changed the rating of the hanger springs to suit. Perhaps use 'softer' springs to more evenly distribute the weight ?
Just some ideas to try.
BobH

Hi Dave

To answer you ?.

The axles had worn about 1 mm undersize, they are fixed to the wheel with loctite and a grub screw along the joint of the wheel I when I replaced the wheels I put in a bigger M4 grub screw, in the same location.

The good axle box had about 0.1 mm ovality when I clocked it that was the movement of the clock that I got so I figured that would be acceptable.

I secured the thread hanger studs in the axle boxes with thread lock and used nylock nuts that shouldn't come undone, but I will keep a close eye on them.

I'll be running the loco this Sunday so I'll let you know how she goes.

Stew

Edited By Stewart Hart on 30/03/2018 09:00:12

Edited By Stewart Hart on 30/03/2018 09:17:14

Hi Bob

The track is a very good one visitors often comment on how good it is, and no one at the club has had this problem before so I doubt its the track.

Interesting comment about the Simplex being front heavy I preloaded the springs with the no weight on the wheels this suggest that I should have lighter loaded springs at the front. I know some people set their springs with each axle in turn sitting on scales so that each axle carries the same weight but we don't have this bit of kit at our club.

Thanks for you useful input.

Cheers

Stew

If you must glue the Oilite bushes in place, the recommended grade is 603. I would press the bush in it's hole, about .001" per inch diametre interference. My feeling is that the Loctite will soak into the sintered bush and displace the oil carrying ability.

Ian S C

I had a similar wear problem it was solved by building a completly new ashpan which was sealed at the back. The original design was open a pond tge ash dropped directly down onto the axel box and caused the wear, it was a very efficient grinding paste. No problems now!