So a while back I took a chance on the plastic version of this gearbox. Here's a couple pics of the gearbox type for those that might be unfamiliar with them. The larger motor is a 550 and the smaller on is 380. The 550 provides straight line propulsion and when the tank turns, the 380 motor kicks in causing the tank to turn. The motor mounting frame gets permanently installed in the tank using the stock HL mounting screw locations. The gearbox then slides in the frame and is secured with two M3 screws locking it in place.
I had heard stories of others having issues with them out of the box. The first one I installed was in my Kranvagn and it worked wonderfully. I've been battling with it for months without failure and I wasn't being nice to it. With that I bought a few more with the idea that if they broke I could cannibalize them to keep a few of the units running. I think I have 6 of them at this point because I got them for right around $70 shipped per unit which was worth the risk for me and it was half of the plastic housing metal geared version. As you can see from the previous images, I installed on in my 3D printed IS-4 build and the first time I started up that gearbox it was making some nasty noises that just didn't sound normal. I popped open the gear side of the gearbox (the other side is the belt drive) and the small first stage gear was already partially stripped.
At that point I started to believe the stories of others saying that the quality was a little questionable. Since I did have a version with the full metal gears in the stash also, I checked to see if the metal gear could be used as a replacement for the first stage gear. It worked and the noise in the gearbox was gone.
That led me down a road of scouring AliExpress for a replacement gear for my metal unit. I was also going to just upgrade the first stage in all of my plastic gearboxes. After counting the gear teeth and calculating the module number I found these gears which should replace the first stage and they were $2.00 each shipped with a 3mm bore:
At this point I say "should" as I ordered a different gear and it didn't fit. I should have these in the next few days to finish my testing. I say finish testing as I opened up another one of the plastic gearboxes and found a problem in the second stage gear. This 3rd unit had completely the wrong gear installed. The bore for the shaft on the second stage was way too big. When I pulled the gear out I found that not only was bore the wrong size, but the gear was missing it's second stage 10T gear. The gear installed had a bare hub when it was supposed to have a reduction gear. With no second stage gear, that gearbox would have no ability to turn. You can see the correct gear on the left and the incorrect gear on the right.
That set me on an other AliExpress search for the second stage gear. Initially I didn't find it and got very discouraged thinking it may be some custom gear HL used. I eventually found the gear on Amazon, but they wanted $95 for it in metal. That was definitely a no go, but at least I knew it existed. Having found that one on Amazon, I eventually found one for $35/gear and that was still not cost effective. I did find a gear that was really close to the one I needed on AliExpress so I inquired about getting the one I needed custom made. I never heard back from that vendor even though it said right in the listing they would do a custom quote. Out of the blue I looked again on AliExpress. Sure enough, the gear I was looking for popped up and more importantly - cheap.
They ended up being about $3 per gear as I bought enough of them to replace all my plastic secondary stage gears. I did receive these gears today and they work perfectly.
The question someone might ask is why didn't I just buy the metal geared version? Well that was a difference of almost double the cost. For about $40, I can upgrade the weakest gears of all my units and have a few spares. When the smaller 1st stage gears come in I can post a verification that those gears also work, but they are the right bore, the right tooth count and the module (pitch) as the other gear.
I did also find metal replacement gears for the output shafts that stay in the motor frame, but I haven't ordered any as I haven't found any pre-drilled for a set screw. I can always drill and tap one myself, but those gears are the largest in the gearbox with the largest engagement face. I don't suspect that they will fail very easily. The 3rd and 4th stage are also thicker gears with a larger cross section making them stronger than the two that I am replacing. Anyway, just thought my pain might help someone fix their deadlined plastic gearbox. :)
I had heard stories of others having issues with them out of the box. The first one I installed was in my Kranvagn and it worked wonderfully. I've been battling with it for months without failure and I wasn't being nice to it. With that I bought a few more with the idea that if they broke I could cannibalize them to keep a few of the units running. I think I have 6 of them at this point because I got them for right around $70 shipped per unit which was worth the risk for me and it was half of the plastic housing metal geared version. As you can see from the previous images, I installed on in my 3D printed IS-4 build and the first time I started up that gearbox it was making some nasty noises that just didn't sound normal. I popped open the gear side of the gearbox (the other side is the belt drive) and the small first stage gear was already partially stripped.
At that point I started to believe the stories of others saying that the quality was a little questionable. Since I did have a version with the full metal gears in the stash also, I checked to see if the metal gear could be used as a replacement for the first stage gear. It worked and the noise in the gearbox was gone.
That led me down a road of scouring AliExpress for a replacement gear for my metal unit. I was also going to just upgrade the first stage in all of my plastic gearboxes. After counting the gear teeth and calculating the module number I found these gears which should replace the first stage and they were $2.00 each shipped with a 3mm bore:
At this point I say "should" as I ordered a different gear and it didn't fit. I should have these in the next few days to finish my testing. I say finish testing as I opened up another one of the plastic gearboxes and found a problem in the second stage gear. This 3rd unit had completely the wrong gear installed. The bore for the shaft on the second stage was way too big. When I pulled the gear out I found that not only was bore the wrong size, but the gear was missing it's second stage 10T gear. The gear installed had a bare hub when it was supposed to have a reduction gear. With no second stage gear, that gearbox would have no ability to turn. You can see the correct gear on the left and the incorrect gear on the right.
That set me on an other AliExpress search for the second stage gear. Initially I didn't find it and got very discouraged thinking it may be some custom gear HL used. I eventually found the gear on Amazon, but they wanted $95 for it in metal. That was definitely a no go, but at least I knew it existed. Having found that one on Amazon, I eventually found one for $35/gear and that was still not cost effective. I did find a gear that was really close to the one I needed on AliExpress so I inquired about getting the one I needed custom made. I never heard back from that vendor even though it said right in the listing they would do a custom quote. Out of the blue I looked again on AliExpress. Sure enough, the gear I was looking for popped up and more importantly - cheap.
They ended up being about $3 per gear as I bought enough of them to replace all my plastic secondary stage gears. I did receive these gears today and they work perfectly.
The question someone might ask is why didn't I just buy the metal geared version? Well that was a difference of almost double the cost. For about $40, I can upgrade the weakest gears of all my units and have a few spares. When the smaller 1st stage gears come in I can post a verification that those gears also work, but they are the right bore, the right tooth count and the module (pitch) as the other gear.
I did also find metal replacement gears for the output shafts that stay in the motor frame, but I haven't ordered any as I haven't found any pre-drilled for a set screw. I can always drill and tap one myself, but those gears are the largest in the gearbox with the largest engagement face. I don't suspect that they will fail very easily. The 3rd and 4th stage are also thicker gears with a larger cross section making them stronger than the two that I am replacing. Anyway, just thought my pain might help someone fix their deadlined plastic gearbox. :)
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