Metal upgrade for a TongDe M60A1 to improve reliability

[keilau]

The Patton tank is an unique topic, but the TongDe design and quality is an disappointment, mostly due to filmsy structure and poorly matched fixtures. I have an early production tank which does not help. I have managed to install the metal gearbox, sprocket and idler wheel. I got the torsion bar brackets from Rich Johnson. I consider myself an experienced Heng Long tanker with good modeling skills. But the TD M60 keeps my hands full.

My persistent problem is the first left road wheel keeps falling off. Not the just the wheels, the whole swing arm assembly will not stay in place. It causes the tank not to run. I purchased a set of metal swing arms from a TD seller. Another disappointment. The road wheel axel pin will not screw into the swing arm easily. Grease does not help. The thread is quite a bit bigger than Metric M3. Anybody knows what size of screw is these?

[RichJohnson]

Wow that is really disappointing.
I have the all metal version and I have driven the crap out of it and not even installed my heavy duty hold down brackets in it yet because I haven’t damaged anything. It’s from the second run where TD started to make changes to the tank models.

You definitely need to upgrade everything to the metal parts.
if the holes are just slightly too large for the m3 maybe use some rtv to hold the screw in place.

[tank_me]

You could also do something like get some styrene hollow tube, cut it to fit in the hole, and use the screw to cut new threads after gluing it in. Or use a solid piece of styrene tube, glue it in, drill a new hole, and use the screw to cut new threads. Just some things to try if the screw hole is stripped.

[Rubicon99]

The Patton tank is an unique topic, but the TongDe design and quality is an disappointment, mostly due to filmsy structure and poorly matched fixtures. I have an early production tank which does not help. I have managed to install the metal gearbox, sprocket and idler wheel. I got the torsion bar brackets from Rich Johnson. I consider myself an experienced Heng Long tanker with good modeling skills. But the TD M60 keeps my hands full.

My persistent problem is the first left road wheel keeps falling off. Not the just the wheels, the whole swing arm assembly will not stay in place. It causes the tank not to run. I purchased a set of metal swing arms from a TD seller. Another disappointment. The road wheel axel pin will not screw into the swing arm easily. Grease does not help. The thread is quite a bit bigger than Metric M3. Anybody knows what size of screw is these?

A couple of questions.

First did you replace the 2 stock nylon arm bushing with bearings? The bushing fit MUCH loser to the metal arms then bearings do. The bearing in all three of my M60s fit rather tightly compared to the stock nylon bushing.

Second did you replace the nylon wheel bushing with bearings? The bushings are under sized and the wheels "wobble" around quite a bit on their axles. The "wobble" actually will cause the axles if not properly tighten to unscrew and the wheel fall off. Tamiya uses a similar design wheel axle to arm setup on a number of their tanks and can have similar issue as the brass bushing wear. Hence why so many people replace the brass bushing with bearings. TD using loose fitting nylon(or plastic) bushing this happens from the start. Replacing the bushing with bearings will illuminate 90% or more of the issues caused by "wobbling". That said it does not rule out the arm could be a poorly molded / undersized arm. This not uncommon even with the metal stock and aftermarket HL arms. I have a drawer full of them that can attest to this.

Yes, the wheel axles can be a bit tight fitting onto TD arms. I had a few that were this way but managed to get everything settled and they are working very well. If the arm does not screw on completely then either it needs to be re-tapped or simply drilled out so the axle can fit in and be glued/fixed in place. Once done you should never have to deal with it again.

Fortunately the newest M60 have many of the "first run" issues worked out and are proving to be excellent running tanks. Keep at it because I know in the end you will have a great running tank.

[keilau]

A couple of questions.

First did you replace the 2 stock nylon arm bushing with bearings? The bushing fit MUCH loser to the metal arms then bearings do. The bearing in all three of my M60s fit rather tightly compared to the stock nylon bushing.

Second did you replace the nylon wheel bushing with bearings? The bushings are under sized and the wheels "wobble" around quite a bit on their axles. The "wobble" actually will cause the axles if not properly tighten to unscrew and the wheel fall off. Tamiya uses a similar design wheel axle to arm setup on a number of their tanks and can have similar issue as the brass bushing wear. Hence why so many people replace the brass bushing with bearings. TD using loose fitting nylon(or plastic) bushing this happens from the start. Replacing the bushing with bearings will illuminate 90% or more of the issues caused by "wobbling". That said it does not rule out the arm could be a poorly molded / undersized arm. This not uncommon even with the metal stock and aftermarket HL arms. I have a drawer full of them that can attest to this.

Yes, the wheel axles can be a bit tight fitting onto TD arms. I had a few that were this way but managed to get everything settled and they are working very well. If the arm does not screw on completely then either it needs to be re-tapped or simply drilled out so the axle can fit in and be glued/fixed in place. Once done you should never have to deal with it again.

Fortunately the newest M60 have many of the "first run" issues worked out and are proving to be excellent running tanks. Keep at it because I know in the end you will have a great running tank.

I have been considering the ball bearing for the road wheels. With 4 bearings per road wheel, it is quite expensive. I have been carefully evaluating the dimension. I think that 7mmx4mmx2.5mm for the axle and 11mmx7mmx3mm for the torsion arm are the cloest fit. Can you confirm that?

BTW, I found the source of the torsion arm falling out of the tank. It is a misprinted torsion bar bracket. The problem goes away when I put back the original TD bracket. It is only one piece out of 12. I am asking for a replacement.

[keilau]

Wow that is really disappointing.
I have the all metal version and I have driven the crap out of it and not even installed my heavy duty hold down brackets in it yet because I haven’t damaged anything. It’s from the second run where TD started to make changes to the tank models.

You definitely need to upgrade everything to the metal parts.
if the holes are just slightly too large for the m3 maybe use some rtv to hold the screw in place.

TD does not use metric M3 like Heng Long does. Their axle pin thread is very close to UK #6/32 in dimension, but does not screw onto a #6/32 nut. If I can figure out what standard and screw size do they use, there will be no problem. I have the tools to retape the thread.

I prefer to purchase a basic plastic version RC tank and do the metal upgrade myself. It may be more expensive, but the fun is in doing it. I had lots of problem in the early days (early 2000) of Heng Long. TongDe is making me to revisit history.

[keilau]

You could also do something like get some styrene hollow tube, cut it to fit in the hole, and use the screw to cut new threads after gluing it in. Or use a solid piece of styrene tube, glue it in, drill a new hole, and use the screw to cut new threads. Just some things to try if the screw hole is stripped.

I am extremely careful not to strip the screw holes. I suspect TD is trying to use #6/32 thread, but did an extremely poor job in manufacturing. I am considering trying a #6/32 tap and die on them. I hope that someone with connection to TD can confirm that for me before I try.

[Rubicon99]

I have been considering the ball bearing for the road wheels. With 4 bearings per road wheel, it is quite expensive. I have been carefully evaluating the dimension. I think that 7mmx4mmx2.5mm for the axle and 11mmx7mmx3mm for the torsion arm are the cloest fit. Can you confirm that?

BTW, I found the source of the torsion arm falling out of the tank. It is a misprinted torsion bar bracket. The problem goes away when I put back the original TD bracket. It is only one piece out of 12. I am asking for a replacement.

The bearing sizes I used. This is on my review posted on RCUniverse.com. I got the bearings through Amazon. They were shipped fast but not cheap given the numbers needed. The cost is one reason I recommend just going straight to the "metal" optioned tank.

[keilau]

Rich Johnson helped me resolved the issue of suspension arm falling off. It was completely my own mistake. I am waiting for the delivery of ball bearings ordered from Amazon. I am still struggling with how to best attach the road wheel axle pin to the suspension arm. I have an idea to try, but not sure if it will work.

[Rubicon99]

Rich Johnson helped me resolved the issue of suspension arm falling off. It was completely my own mistake. I am waiting for the delivery of ball bearings ordered from Amazon. I am still struggling with how to best attach the road wheel axle pin to the suspension arm. I have an idea to try, but not sure if it will work.

Rich showed me the photo you sent him because I have more hands on experience with those parts. I did the same thing twice before I realized there was a difference in the two parts.

Bearing will "tighten" up the wobble of everything and you will see a pretty good performance gain.

The axle? You will figure it out and in combination with the wheel bearings it will probably never be an issue again.

[keilau]

I am making some progress assembling the metal swing arms. The thread on the axle pin is a M3 thread, but it was machined so roughly that I kept measuring its major diameter as 3.6 to 3.7mm. I took a 400 grid sand paper to clean the threads on the axle pin carefully, I finally mic a consistent major diameter of 3.30mm, the standard diameter of a M3 screw. It is very important to use extra fine grid sand paper so that you only clean up the roughness of the screw without removing material from the thread.

After determining the screw size, I re-tap the hole on the arm to smooth out the thread. But the screw still would not go onto the arm smoothly. Close examination reveal that the screwtip has a concave shape. After I grinded off the sharp edge on the screwtip, the pin goes in smoothly and at a perpendicular angle.

I have 4 pieces of leftover 7mmx4mmx2.5mm ball bearings from other project. It allowed me to test assemble 2 swing arm/road wheel pieces. The other 10 arms will have to wait for the arrival of the new bearings. I finally can breathe a sign of relief.

[keilau]

The ball bearing inner diameter is 4mm, but the not so smart autocorrection keeps changing it to 6mm when I save.

The concave shape is on the tip of the screw, not the head. Another smart correction problem.

[keilau]

Rich showed me the photo you sent him because I have more hands on experience with those parts. I did the same thing twice before I realized there was a difference in the two parts.

The torsion bar bracket set you designed work very well. Rich did a good job packaging and even marked L or R on each individual piece. I have no excuse for the mistake I made and not noticing it early.

[RichJohnson]

Well Keilau, I have to admit that was not me that packed and labeled them.
As I said, JVM made them up at Rubicon's request after he broke that one backing up.
So I sent the photo first to JVM and they told me no chance of a miss print there are only two designs and it looked like it was probably the opposite side. So then I sent the picture to Rubicon to double check since JVM hasnt really done anything with them in months since they made the run of them for us. Rubicon confirmed that was an opposite side part.
JVM had the parts packed up the way they were and marked and at the time warned me it was easy to put them on the wrong side if your not careful. I guess even Rubicon says he did that too.
I would like to get more from them next time they have this stuff but they told me it might be a bit till they get that mix of resin in again. They make our model tank parts often from leftovers of larger commercial print jobs so that makes our parts affordable but we have to wait for them to have a commercial job using that material.

[keilau]

Well Keilau, I have to admit that was not me that packed and labeled them.
As I said, JVM made them up at Rubicon's request after he broke that one backing up.
So I sent the photo first to JVM and they told me no chance of a miss print there are only two designs and it looked like it was probably the opposite side. So then I sent the picture to Rubicon to double check since JVM hasnt really done anything with them in months since they made the run of them for us. Rubicon confirmed that was an opposite side part.
JVM had the parts packed up the way they were and marked and at the time warned me it was easy to put them on the wrong side if your not careful. I guess even Rubicon says he did that too.
I would like to get more from them next time they have this stuff but they told me it might be a bit till they get that mix of resin in again. They make our model tank parts often from leftovers of larger commercial print jobs so that makes our parts affordable but we have to wait for them to have a commercial job using that material.

The RC tank hobby is such a small market segment in overall RC hobby, there is no money to be made. I really appreciate what you and Rubicon99 do to make our hobby more fun and affordable.

[keilau]

I received the road wheel ball bearings (7mmx6mmx2.5mm) from Amazon, will start reworking the torsion bar suspension soon. I ordered the 11mmx7mmx3mm ball bearings on e-bay shipped from China. It will come much later. I will do the road wheel ball bearings now and the torsion bar bearings later.

[keilau]

I installed the first 4 road wheels, but not without some struggle. The first 3 went into position with a breeze.

In the original plastic swing arm, the axle pin was held in place with 2 tiny set screws. I used high quality jeweler's screw drive and got the 7 set screws off easily. But the 8th set screw will not come off. (Apparently, the set screw stripped the thread on the plastic arm.) Finally, I decided to destroy the plastic arm to get it off. After clipping off some outside plastic, I used a gridding stick on a rotary tool to finish the job. I worked carefully to avoid damaging the road wheel.


I have 8 more road wheels to install.

[Rubicon99]

I installed the first 4 road wheels, but not without some struggle. The first 3 went into position with a breeze.

In the original plastic swing arm, the axle pin was held in place with 2 tiny set screws. I used high quality jeweler's screw drive and got the 7 set screws off easily. But the 8th set screw will not come off. (Apparently, the set screw stripped the thread on the plastic arm.) Finally, I decided to destroy the plastic arm to get it off. After clipping off some outside plastic, I used a gridding stick on a rotary tool to finish the job. I worked carefully to avoid damaging the road wheel.


I have 6 more road wheels to install.

Why RichJohnson and myself recommended ordering the "metal" edition from the start. It's a lot of time and expensive to add the upgrades later.

Before you re-assemble the #5 & 6 suspension arms (on both sides of the tank) back onto the hull consider also adding "down travel" stops to ensure you do not have a situation that causes those arms to over rotate down and forward causing them damage to the torsion bars and associates components.

[keilau]

Why RichJohnson and myself recommended ordering the "metal" edition from the start. It's a lot of time and expensive to add the upgrades later.

Before you re-assemble the #5 & 6 suspension arms (on both sides of the tank) back onto the hull consider also adding "down travel" stops to ensure you do not have a situation that causes those arms to over rotate down and forward causing them damage to the torsion bars and associates components.

I did not get the metal version from dklmrc.com because I was put off by the $200 shipping. Ironically, I have paid more than $200 in shipping for the TD M60 and parts. I have no regret because I really want ball bearings on the wheels.

Do you mind to show me the design of your "down travel" stopper? Thank you in advance.

[Rubicon99]

I did not get the metal version from dklmrc.com because I was put off by the $200 shipping. Ironically, I have paid more than $200 in shipping for the TD M60 and parts. I have no regret because I really want ball bearings on the wheels.

Do you mind to show me the design of your "down travel" stopper? Thank you in advance.

I made a simple brass ring that slips over the hull extension as shown. It is held in place with epoxy resin (not yet addded in this photo).

Note: the open section on the bottom of the brass ring actually goes at the top. This was a photo taken of the opposite side ring as a basic illustration.

Adding the travel stop ring prevents this from happening. If I had backed up any further I would have broken a few internal parts.