Gearbox rebuild

[windmill]

I noticed HL gearboxes are a bit sloppy and noisy with some unevenness when running straight. Decided to go through them replacing the bushings with flange bearings, add shims, and clean things up in general. It was pretty straight forward, but the shafts on the gears are 3.5mm, and I could only find 4mm ID bearings, so I made press fit bushings from brass tubing. The gearbox needed to be drilled to accept the 7mm OD flange bearings.
Once finished without the motor installed I could flick the input gear and the entire gear train would spin freely. Up and running there's a major reduction in gear noise, steering is smother and crisper with less speed loss, and will creep smoothly at a snails pace now.

It was worth the effort.

[karltrek]

I noticed HL gearboxes are a bit sloppy and noisy with some unevenness when running straight. Decided to go through them replacing the bushings with flange bearings, add shims, and clean things up in general. It was pretty straight forward, but the shafts on the gears are 3.5mm, and I could only find 4mm ID bearings, so I made press fit bushings from brass tubing. The gearbox needed to be drilled to accept the 7mm OD flange bearings.
Once finished without the motor installed I could flick the input gear and the entire gear train would spin freely. Up and running there's a major reduction in gear noise, steering is smother and crisper with less speed loss, and will creep smoothly at a snails pace now.

It was worth the effort.

Great idea! Could you provide links to the where you got the parts?

[Rubicon99]

Great idea! Could you provide links to the where you got the parts?

Tagien tanks has the flange bearings you need to convert the gearboxes. Look in their Tank Parts section on you will find them.

[windmill]

I was unable to find anyone who had the Tagien/Heng Long bearings in stock, so I got generic bearings, shim washers, and brass tubing I could adapt from uxcell on Amazon.

[Rubicon99]

I was unable to find anyone who had the Tagien/Heng Long bearings in stock, so I got generic bearings, shim washers, and brass tubing I could adapt from uxcell on Amazon.

Currently in stock at Taigen tanks:

[windmill]

Currently in stock at Taigen tanks:

Those are the large 5mm X 9mm X 3mm (ID X OD X WD) for the drive shaft (red arrow).

The issue I had was finding the small 3.5mm ID bearings for the gear shafts (black arrows). I ended up getting 4mm X 7mm X 2.5mm bearings,https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 and shimming the 3.5mm gear shafts with 4mm brass tube bushings https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I used the 4mm X 8mm X 0.5mm washers https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 to compensate for the thinner flanges on the bearings, and to space the gears so they don't rub laterally which is the source of most of the noise they make.

Washer shims on gear shafts, and plastic spacer needed on right driveshaft.

[karltrek]

Thanks for the links! I will give it a try.

[windmill]

Thanks for the links! I will give it a try.

It's not too difficult, the brass tubing bushings are a pretty tight fit in the flange bearings, buffing the brass tubing with 400 grit before cutting, and a dab of oil will help when pressing them in.

[karltrek]

I did the upgrade. Very easy to do with a drill press. I found it easy to press in the brass tubbing after reassembling the gearbox.

[windmill]

I did the upgrade. Very easy to do with a drill press. I found it easy to press in the brass tubbing after reassembling the gearbox.

Sounds good.

I found with careful shimming with the washers, most of the gearbox noise can be reduced. It seems most of the noise comes from the sides of the gears rubbing each other, rather than from them meshing.

[karltrek]

After running my tank for a while with the modified transmissions I opened her back up to do some maintenance and I noticed a couple of the brass tubing inserts had backed out. Trying to figure out a solution for this.

[windmill]

After running my tank for a while with the modified transmissions I opened her back up to do some maintenance and I noticed a couple of the brass tubing inserts had backed out. Trying to figure out a solution for this.

I pressed them in from the flange side with a small jewelers ball peen hammer leaving the thickness of a shim washer sticking out. It seems to flare the bushing just enough to keep them from slipping out. I had considered adding a dab of superglue when I first did it, but so far, so good.