AF diesel die cast axle bushing replacement

Here hopefully is a picture of the jig that I use for re-bushing my diesel chassis.

The chassis is locked into the jig so that it can't move. I have a selection of slip bushes which are used in the jig to insert an 8mm oilite bearing and then take out the corresponding side to accept the stepped axle journals.

I have done quite a few chassis and never had a failure so far.

Did you try Doug Peck at Port Lines Hobbies???

Marty

STEW1957: Is that the Hobby Horse kit?

Hi CW, yes it is the kit from HH. 

Here are a few tips that may be of help when you strip down a chassis that I have learnt over the years.

Try to only pull off two wheels on one side, the side that has the solid wheel with an insulator that fits on the axle, the other wheel being the PM wheel will also have an insulator. Reason for this is that if you pull the solid wheels from the axle they don't always go back on with a tight fit. 

The axles depending on how worn they are can cause problems with the new bearings and they will wear out prematurely. They tend to suffer more from electrical wear than mechanical as the current goes through them to get to the chassis and this causes pitting, even with the sliding pickups. At this point it is best to change them for new ones if you can still find them. I have quite a few for when I need to use them but then a number of these are not perfect either. I have seen on the larger journal what looks like a scratch line on the full width which I can only presume is where the cutting tool used to machine them has been pulled back once it has finished the job. You can feel it with your fingernail and if used as is will again chew up a new bearing as it acts as a cutting tool itself.

On reasembly I also add some shim washers either side to reduce excessive side play on the axle/wheel assembly, this helps to keep the axle gear centralised in the middle under the worm.

 

This is is what happens to gears when the chassis axle hole becomes excessively worn. The two gears on the left came from a 372 GP7 which I picked up many years ago. 

The gear on the left shows that it had been meshing right up into the worm, which over time has worn the teeth to point and reduced the height compared to a new gear on the right. Also the left gear leaning to the right indicates it was not centred under the worm fully. The middle gear also leans slightly to the right but was not far from the centre. 

A chassis in this condition will give poor performance, runs slower which means it will be pulling more current which further compounds the problem. You also run the risk of possibly burning out the armature if left like this from extended running.

In some respect the diesel chassis was not one of Gilbert's finest bits of engineering, to be honest they can be a PITA to get running well at times.

 

Here is a picture of a worn axle. It has scoring on both journals, the right side smaller one is more noticeable. If you used this one again as is it would not take long to make a mess of a new bearing inserted into the chassis

 

Got a worn truck. Here is a picture of the worn bushing. Thank you UKAFLYER for your pictures and advice.  I will post pictures as I progress using this Hobby Horse tool.

Hello STEW1957,

A couple more pictures to show how a well worn chassis can look. Your one actually doesn't look too bad considering but will give you some good practice on rebuilding these chassis.

A new axle measures 4.55mm for the large journal and 4.09mm for the small journal on my micrometer if you need some reference data.

On the bottom picture the large journal hole measured top to bottom at 5.12mm and 5.55mm left to right.

Before you start to reassemble it back again let us know how it goes and I'll go through how I cleaned up the axles to remove as much scoring as possible before I got a supply of new axles, it isn't what I would call good engineering practice but then I had no other options back then and it did work.

Below is chassis showing small journal

Below is the large journal hole, again seen better days.

Hello STEW1957,

i just had another look at your chassis and I can't quite work out which one it is but I think you may have an early chassis with a part number of PA11412, if it is then it will probably have the early steel bearings that can be knocked out, replacements for these can be purchased from SNS, who also specialise in rebuilds.

The chassis you need which is the more difficult to rebuild is the PA12B065 which has the holes machined direct into the chassis.

Good eye UKAFLYER. It is a 11412 frame.  The frame appears to have two pressed fittings. The axle bushing, then a bushing for the axle bushing pressed into the frame. Is this correct?  Do you have the part number for the left and right axle bushing? I would prefer not to drill if simple rebushing can be done. 

I have done numerous bushing replacements on Lionel motors and frames. In the past several years I have repaired many PAs that are getting to the point where the slop is so bad it is starting to affect their operation. Thank you for your sharing.

 

Hi,

go to this link and contact them for availability of early knock out bushes. I have never seen ones with the steel bush inserted into another metal sleeve, normally all the ones I have done have the bush with key way inserted direct into the chassis. The new bushes at below are brass and do not have a key way, it isn't needed. There are no part numbers for these bushes.

http://snstrains.com/Services/rebushing_services.html

Thank you for the link. I wonder if this truck has been serviced with replacement bushing in the past. The axles are heavily scored so they will be replaced. From what you posted earlier damaged axles will quickly damage the new bushings. I have ordered several axles from Portlines Hobby.

So the frame PA12B065 has no bushings, the axle rotates directly on the casting?

Yes, the axle runs directly on the pot metal casting. The design did not take into consideration the electrical arcing that happens--it's not really "wear" that causes the problem! I have considered adding wire wipers on the back side of the wheels to reduce that arcing, but so far the design is only in my head! I've also considered making the new bushings a bit long, so they stick inside where the gear goes to provide a "centering devise" to keep the gear in line with the armature. I have yet to put these ideas into practice to see if the ideas are any good. With my present situation, I probably won't get around to testing the ideas for at least a year, so I provide them here to see if anyone else wants to give them a try.

This is what I had to resort to many years ago to clean up axles which were scored and looking a little worse for wear, not the best engineering practice but sometimes there is no alternative.

I had access to a small lathe and used to put the axle in without tightening too much to make a mess of the knurled end. I would then have strips of wet and dry at about the width of the journal at 1000, 1500 and 2000 grade. Start with the 1000 and keep it wet and just wrap it around one journal at a time to remove the high points. I would then do the same with the 1500 and 2000 grade until it was cleaned up and looking smooth. The best way I found how good it was is simply to run a finger nail over, it is surprising how sensitive it can be to find imperfections still. Also, just feeling it also can help. 

It isn't the proper way but when you don't have access to new ones it was better than nothing, perhaps a chapter of my repair days best forgotten.

I am still running a fair few of these and they are still holding up well.

The Hobby Horse bushing kit is not needed with the diesel truck 11412. The bushings in this truck press out easily. Port Lines Hobby sells the bushings as a set of four. The bushings come predrilled for the left or right side. 

Still looking for diesel truck PA 12B065 to use my tool. 

When you put the bushes in remember to put them in the right side. Looking at your picture with the bushes removed, the new ones that go this side have the larger hole.

I have a question. Why are there two journal sizes on the axles.

And for those who not know the later motor chassis were equipped with bushings. These are the later American flyer by Lionel with the CAN motors. The bushing are recessed on the wheel side. You have to pull the wheel to see the bushing.