Armortek

Hi Lucian, that ball set sounds interesting.
I have come accross captive ballsin the past but cannot think where, thats what happens when you get to my age
The stock size lazy susans are either to small or to large on the inner diameter for the turret.
Slew rings may turn out to be to exspensive
If all else fails i may try and turn up a couple of rings and fill the lower half with ball bearings . Would need to do it on the quiet while the manager is on a trip

Having chatted to one of our customers who specialises in plastics and the like , a more suitable material would be PTFE for the turret ring . It seems that if 2 peices of PTFE are in contact with each other the effect is like , and I Quote " ice on ice ". The material is easily machined and very cost effective compared to a bearing ring.
I should have a peice of material within the next few days and will machine up a ring to replace the bronze ring and another thin ring for the underside of the turret.
Once done i will post again.

I am very interested to see how a PTFE ring turns out and how well the turret operates with it. Please do post your results and pictures!

- Alan

Hi Guys
thin ring of PTFE should do the trick just in between the base of the turret and the brass ring that is glued in the deck of the tank.
I am thinking of using 1mm thick sheet.My other idea was to use
10 mm dia PTFE rod and make 4 or 5 plugs to fit in to holes I would drill in the base of the turret.so they slide on the brass ring again this would be a cheaper option and would have the same effect.
I am having some problems on my Panther turret with it binding between the base of the turret and brass ring.
I will be interested to here what works for others.

I was thinking that David was going to replace the brass ring completely with a PTFE ring of the same size. I'm wondering if the material is strong enough to take the weight of the turret though. I wonder if it would start to crush and mushroom out over time. I'm very curious to see how these experiments turn out.

Alan

I think you will find that PTFE to make either a washer or complete ring may be expensive. It will either have to be trapanned from a sheet or cut from a tube. If you make a complete ring it will have to be fixed to the deck using small screws as I don't know of an adhesive that sticks PTFE very well. I would argue that a well greased brass bearing would have the same coefficient of friction as the PTFE bearing.

The first thing I would do is to screw and glue the existing brass ring peices to the deck, relying on glue alone would be dodgy as the deck flexes when the model runs and when it is removed for access to the hull. Eventually a pure glue joint may fail. With this done the next stage is to try the turret in the ring without the large gear fitted and make sure it rotates freely in the ring. I had to scrape the brass around the joint areas of the bearing as it had closed up a little. After this stage the turret should rotate freely through 360 degrees with little side to side slack. Next fit the turret gear and turret turn motor/gearbox, but do not tighten the turret gearbox pinion on its shaft. Fit the turret and try turning it with the gears in mesh, it should rotate freely through 360 degrees. Mine did not initially and it was due to a small excentricity on the large gear, so I slackened its retainling screws on the truuet then tried the meshing again and it centralised the gear and freed everything up. You will find that the old small turret rotating motor on the mid and early Tigers will have just about enough power to turn the fully assembeld turret.

Hi Alan,

With an allowable dynamic surface pressure of up to 300 N /mm2 , load shouldn't be the problem

Ad,

I'm not sure what you mean by the dynamic load, if its the turret weight, or downward force over area (pressure) then I think I understand. My approach is just to ensure that everything is turning as freely as it can. I can't see PTFE really improving the overal situation over a greased brass bearing. Even in this situation the reality of it is that the turret motor in my tank does struggle a little. A more powerful motor/gearbox would give a better response and better speed control when using an ESC, as I do.

Hi Alan
I was wondering if the Panther turret is lighter than the Tiger one you have?
Mine seems to drag but I have not yet fitted the motor.Just turned by hand.
I am getting some score marks on one position of the alloy turret base
where it is rubbing the Brass ring.
On the Panther Kits the Brass ring is one piece on mine It has been glued and screwed down and measured flat.
This is why I was wondering about PTFE as we use it a lot at work for this sort of thing.
It could just be bedding in but I am not very happy with it as is.
This is my first big tank build
Any ideas?

Thanks
Derek

Hello Allan,

I was merely responding to Alan's doubts on the load carrying capacity of solid PTFE parts. I agree that it has no substantial advantages over brass parts in our application. It only does not require lubrication, which might be a point of consideration btw. That is all

Derek,

I think the Panther turret may be lighter than the original Tiger turret as it is a substantial alloy casting. I ended up drilling loads of blind holes in my turret to knock out some of the wieght.

You certainly need to work on the turret to get rid of any binding or scoring. If you have a vernier you can check for ovality of the turret ring and turret base and scrape this out. I used scrapers rather than a file for the brass, its quicker and easier, but then again I did a fair amount of scraping when I worked in a workshop. Take your time to get the best compromise between a good running fit and minimum slack in the turret bearing.

In the last few days i have machined 2 PTFE rings. One has a small lip as per the brass ring, and the other was plain. Both have the same bore size as the brass ring. The outer diameter was just made to a nominal 355 mm.
At the same time as fitting the PTFE rings i decided to replace the switcher unit with a good quality ESC.
I decided to try fitting the turret without fixing either of the PTFE rings as the weight of the turret and the fact that the lower ring has the lip as per the original brass ring , they have no place to go. Also as 2 surfaces of PTFE in contact with each other have little or no friction i had nothing to lose .
The results are unbeleivable , i have gone from a sticky , jerking turret rotation to a very smooth variable speed rotation.I am well pleased with the results.
Some might wonder at the cost, well i was fortunate that i was given the material for nothing, as it was an offcut from a bigger peice, and the job had been completed. Had i needed to buy the material , it would have been around £50. Even at that price i still think it would have been worthwhile , as the turret rotation problem was getting to be a pain.
If anyone out there wants dimensions , please feel free to email me
Thanks to all who have taken an interest in this one.

Hi David
Do you mean that you removed the brass bearing completly
or did you use you PTFE bits over the brass bit.
Also what thickness was the plain ring ans what thickness is the
lipped ring.
Could you post a picture please
Glad it worked for you.
Derek

Hi Derek.
If i knew how to post pictures on here i would do so , im afraid i am not that good at finding my way around the pc .
Haveing said that i will try to put some up , possibly in the gallery.

I removed the brass ring completely and machined a similar ring with the lip from PTFE. I did make the thickness slightly thinner than the brass ring, but increased the outer diameter to 350mm. The plain ring was 2 mm thick, again 350mm outer diameter with the same inner dimension as the original brass ring. So now I have two rings that sit face to face , giving possibly the lowest friction except for possibly a ball race.
The only noticable difference is that the turret is now possibly 1mm higher than it was originally, but i would prefer to live with this than the slugish, jerky turret rotation i had before . As to the wearing properties , time will tell, but i am fairly certain that the rings will stand up to the job.

For those that want to machine thier own rings , the PTFE spec is "Virgin PTFE " in 2mm sheet and 5mm sheet. The thickness of the 5mm sheet is usually fairly genourous and comes out at around 5.5 to 6 mm thick.

Hope this is of help

Hi David
Its a big help.
I work in a research group at a university so I have the sheet PTFE
and as I have my brass bearing glued and screwed to my deck
I think I will try a plain ring first sandwiched between that and the turret base.
Thanks
Derek