Panther loosing its tracks

[Armortek]

Gentlemen

Everything Bob says concerning the fit of the idler shaft in its bearing is correct. Ideally it should be a closer fit. However, due to way that the track tension load is carried through to the adjuster, it does not result in an idler misalignment, and does not cause track shedding. Improving the fit will of cause do no harm, but I doubt it will make any difference either. It certainly did not when we tested the theory on a model here. The bump stop brackets are an issue. The top fixing and section are best removed. Do this and get the tension correct and you will have no problems with track shedding.

These issues have been dealt with on the Jagdpanther.

Mark

[Ad Wouterse]

Hoi Marcel,

If you need the material to shim the idler shaft you should look for thin brass sheet ( in Dutch "latoenkoper"). Any professional hardwarestore should be able to supply that in various strengths (from 0.05 mm upwards). I might be able to help you out with a few strips of 0,2 mm.

The "perfect"solution would be new idler shafts with the correct tolerances. That can be arranged as well

Anyway, just drop me a PM.

[Steve Norris]

Gents,
I have had my Panther running for about six months now and apart from the tracks requiring tensioning have had no issues with them. I removed the top section of the 4 bump stop brackets as these were being struck by the tracks, i also removed the track pin bumper from each side. The drive system now is extreemly smooth and has not suffered from track shedding.
I have tensined my tracks so that they come off the drive sprocket and touch the 3rd from the front outer road wheel first.
Hope this info helps
Steve

[Tim Bowman]

Mark and Steve

Thank you for the input. I haven't been able to get my track to shed again. Obviously, my tension was simply way too loose. I'll modify the stop brackets and then all should be just great.

regards

Tim

[Derek Attree]

Hi Steve
Could you show a picture of the mod to the bumpstops
I had changed the hex head bolts to counter sunk on mine
but I have not changed the actual shape and size of them.
I have also reduced the thickness of the track pin bumper on the hull sides by milling of the back face by 4mm after somthing Lee mentioned.

Thanks
Derek

[Robert E Morey]

Derek,
I posted a photo in my gallery on how I modified the bumpstops. As Steve described removing the top "arm" portion. I don't know if this is the official Armortek endorsed modification, but it looks like it will help. The bump stops behind the drive sprocket look to be the critical ones for this (or similar) modification..
Bob

[Derek Attree]

Hi Bob
Thanks for the photos I see what you have done.

Happy new year

Derek

[Roland Wallick]

Marcel, Tim, and others,
I was installing the rear idler shafts in my Panther, and I realized something that Marcel touched on in the beginning of this post. That is there is an alarming amount of clearance between the rear idler shaft and the brass idler bearing. I measured .020" (0.5mm) between shaft and bearing on my parts. This in my opinion is way too much gap, and could be a contributing source of the track shedding. This amount of clearance could potentially translate into 1-2mm of movement at the idler wheel edge when the track is under extreme tension (i.e. during a turn).

A smooth running track (or conveyor belt) depends on the drive wheel and idler wheel being perfectly parallel with each other and aligned side to side. As you increase the tension in the track, the force from the track will try and make the excess gap (between idler shaft and idler bearing) as big as possible - basically pulling the idler wheel toward the front of the tank - and no longer parallel with the drive wheel. Since the idler is no longer parallel the oncoming track teeth will attempt to "climb" over the tilted idler wheel. Bingo, now you have a shedding track.

The internal track tensioning screw and mechanism may take up (reduce) some of this clearance problem. But I think something needs to be done to reduce the excess clearance at the source - the shaft and idler bearing -reducing the clearance between these two parts cannot hurt anything. The idler shaft within the bearing should be a very snug fit, with just enough clearance (.005"or so) to allow the idler shaft to rotate, but with very little front to back play.

Short of remaking the idler bearing, I came up with an idea. I just happened to have some .008" (.20mm) tin sheet in my shop. Brass would be better, but tin is a fair bearing surface as well. I cut a piece slightly less than the width of the idler bearing and about 2.3" (58.4mm) long. Then roll it into a tube and slip it onto the idler shaft. Slide the shaft and shim into the bearing.

Time will tell if this "shim" is a fix or not, but the fit of the idler shaft to the idler bearing is a lot better with the shim, and definately cannot hurt the performance of the track under tension.

I dont have my track on yet but I have noticed the slop in the idler shaft. I dont think tweeking on the adjuster screw is a good idea, it will force your shaft to run crooked and cause lopsided wear on the bearing.
I dont think new bearings would cost that much to make, they really are needed. I think your tin will wear out and then wear on the idler shaft.
I would think these bearings could even be made of a good plastic like Delrin. This is a critical item is the drive system.

[Robert E Morey]

Rolland,
Your suggestion to make new bearings is probably the best long term solution. Shims are a stop gap solution, but sometimes they work fine in certain applications.

Yes the bearing could possibly be Delrin plastic, with one big consideration. The idler shaft is under considerable torsion at the idler bearing location -due to track tension. I'd be afraid that a plastic bearing would want to twist out of the two M3 screws holding it in place to the hull. If you'd want to use plastic, I'd suggest adding another two M3 screws (4 total) to the bearing to help distribute the twisting force on the bearing. Brass or bronze is still probably the best choice for the idler bearing.

As for the shims wearing out, I'm not sure that they will. The ider shaft is rotating very little inside the idler bearing. Once the track tension is set, then no more rotation of idler shaft will occur until the tracks wear and loosen and the idler wheel needs more tension. But even then the rotation of the idler shaft is not even 1/4 of a rotation, so little wear on the shim from rotation will occur. Over the life of the tank the idler shaft will rotate very little. As long as the shim is good bearing material (ie brass for example) then I think the shim will last as long as the rest of the mechanism.

If you decide to experiment with plastic bearings or remake a new brass set completely -keep us posted on how it works.
Happy New Year to all.
Bob

[Roland Wallick]

Bob I agree with you about them twisting out, my first thought would be to insert the Delrin into a metal sleeve and mount that part to the side of the hull. Maybe even use the existing part and ream it out.
Either way not something I will look into doing untill the tank is closer to done. And that is a low priority at this time. Just want to get it on its tracks so I can get it out of the kitchen.

[Marcel de Groene]

Hello guys,

I have been following all the suggestions with great interest. Ad Wouterse has been so kind to help me work out a "long time" solution and we are currently working on making new Idler shafts, with minimum clearance. This shaft will be 1 mm longer on the outside and 1 mm shorter on the inside to compensate for the track tension screw. This way I'll have more track clearance from the hull and the hole section will be exactly in line with the drive sprocket. We use 0.5 or 1 mm washer to obtain this. Hope to get the parts within the next two weeks. Larger production will not be possible since it's done on a friend to friend basis. So I hope that this solution works out fine and we can share the experience/solution.

Marcel

[Robert E Morey]

Rolland,
Thats not a bad idea - drill out the existing bearing and put a closer fitting "sleeve" into the existing brass bearing. The sleeve could be plastic bearing material or brass/bronze. Epoxy and/or press fit the sleeve into the existing idler bearing? I hear you on the wanting to get her running - I'm getting that fever too.

I'm not yet to the point where I'm tracks up, but if the idler does need to be further from the hull then something else must be considered. Then Marcel may be right and the idler shaft may have to be remade or other modification considered. Hope this is not the case.

Marcel, could a 1mm spacer washer be placed behind the inner most idler wheel bearing? This in theory would move the idler wheel 1mm outward?. But can the remaining bearing and everything else fit together? Just thinking out loud here.

Tim, this would be a good time to add any idler wheel offset to the early idler design you're working on!
Bob

[Armortek]

Gentlemen

We must advise caution here. The above discussion gives some very fine technical solutions to problems which do not exist. You are all entitled as individuals to do make whatever mods you like to the models. The official advise is as follows:

Do not modify the idler or bush in order to reduce risk of track shedding. It will make no difference.

Do not add washers, spacers or mod parts to change the distance of the idler from the hull. This action will most definitely have a negative effect.

We would strongly advise that builders assembly the parts as supplied and set the track tension correctly.

[Ad Wouterse]

Gentlemen,

I feel the need to add some comments to the recent posts in this thread.
As Mark truly warns for any rash actions,we will approach the "problem" very carefully. The first step will be to replace the idler shaft housing by a version with a correct clearance. If that solves the problem in combination with the recommended track tension... great.

We also noticed a slight misalignment of the right hand idler towards the inside . On its own that should not be the cause of the track shedding, but it might add up to the shaft clearance. As we have to turn on the old lathe anyway, why not make a few thin brass spacers at the same time ? Just in case.

[Allan Richards]

To me the Panther track suystem is very similar to the Tiger system with the double track horns and interlaced wheel arrangement.

I bought the original early Tiger and didn't like the original wheel spacers and road wheels flicking in reverse over undulating ground, so I made new wheels spacers to cure this problem. I had to make sure all the road wheels, sprockets and return rollers were aligned, and once done there should be not tendancy for the tracks to want to run off. I started with the sprocket and fixed this first and measured distances from this to set the position of the road wheels and return rollers, using washers and the new spacers. I used a straight edge to check that everything was aligned and also the road wheels square to the tracks. On two road wheel axles the wheels were slightly out of square due to the threads in the axle assembly and also the bearing block being out of line, but the brearing block problem will not happen with the Panther. The other thing to check is that the wheels remaion square when side loads are put on them but again this should not be a problem with the Panther due to the better design of the single piece road wheel axle bearing block and also the road wheel bearings themselves.