Instructions for 3:1 heng long gear conversion

[SovereignZuul]

I swear I read a thread but now I can't find it. I bought these for converting my metal heng long gears to drop the ratio 3:1. Was just looking for the instruction on proper installation. I appreciate any help, thanks!

http://www.rcsmart.com/ebay/metalgearbox02.jpg

[Dietrich]

Hi,
You can use these gearboxes ...BUT....unfortunately if the output shaft on the drive from the unit has not been 'turned down' in diameter by the supplier then you will find that the gears supplied are the wrong 'Pitch' for the Heng Long gearboxes and the teeth will not mesh properly causing a very loud noise and ultimately loads of damage. I will just check the site address on the photo and get back to you......

In the meantime .....this is a very early post of mine on how to convert the standard metal gearboxes to 3-1 reduction...which might be what you are referring to....
viewtopic.php?f=38&t=4981
Alb.

[Dietrich]

Hi,
It took a while to find the Ebay seller....
I am sorry to say that you are going to have problems with this....

metalgearbox03.jpg (36.84 KiB) Viewed 1728 times

The output shaft is the 3.96mm....and unfortunately the PITCH of gears with a 3.96mm ID will NOT actually fit into a Heng Long or Tamiya gearbox. Basically the spacing of the teeth in the gears is different so they do not mesh properly. The gears are designed for helicopters I think......and are not suitable for tanks.
You need to reduce the diameter of the 3.96 mm output shaft to either 3.2mm or 2.3mm then you can get the correct 46 pitch gears to fit onto the shaft......sorry to be the bearer of bad news....
I did exactly this a few years ago....fitted it all and started the tank....the noise was alarming !!,as was the vibration from the gear teeth smashing into one another and then being forced into one another.
.
Now to the solutions......

You can either get a machine shop to 'turn' the output shafts down for you...probably NOT cheap or even easily achieved.....OR.... Firstly, buy the correct 'Pitch' of gear that you need in the 3.2mm or the 2.3mm .................
Then you have two options......
1. Drill out the gear to match the shaft......best to use the 3.2mm size as there is more metal to drill out.....but it is very difficult to drill exactly centrally and any offset will case the gear to bind and stick.....
OR
2. Fit the reduction gearbox to a 'spare' electric motor and power it up......Now again you have two choices ......spend ages with a metal file trying to carefully and evenly reduce the shaft diameter so that the new gear will slip onto the shaft.......or the second faster but more risky option is to use an angle grinder to VERY carefully remove the excess.....it is MUCH faster but it is very easy to overdo it or to angle the grinding so that you get a tapered shaft....( Ask me how I know )...use either a new cutting disc or use the FLAT top of the grinding disc.....Its a real pain In The Ass that there are no 46 pitch gears made in this inner diameter of the 3.96mm diameter....that I have yet found...but I would LOVE to be shown some....because these gearboxes are a superb little bit of kit.
.
One more thing about them.........
When fitted to the motors they do need additional clearance on 'Top' so you may have to cut additional bits out of the tigers top hull.......I fitted them to a Panzer III...JUST and I mean JUST with serious cutting of the top.
If you need anymore help please just ask.
Alb.

[SovereignZuul]

WOW! That is an impressive reply, thanks so much for taking the time!

Sad news, but understood! I knew I would have to reduce the ratio of the shaft to fit the pinion gear, but I didn't know the pinion gear would fail so horribly once completed! You saved me a lot of time trying. I had already disassembled the whole thing last night and was just getting read to start filing down the shaft today.

I'll save the parts, maybe I can do your 3:1 conversion for my PZIV which has the plastic gearboxes. For the Tiger I'm going to just buy a premade gearbox today. Question is, which is better? The steel gears from Taigen or the brass ones from Mato? I'll be doing more research right now.

[Dietrich]

Hi SovereignZuul ,
I think that you might have misunderstood me... .....once you have turned down the shaft on the output from its 3.96mm Diameter to the 3.2 or 2.3mm diameter you CAN buy the correct size of 46 pitch toothed sprocket that you need. The gears that are supplied with the gearbox ARE 46 pitch tooth and are actually meant to go onto the electric motor that you fit the drive the gearbox

Its the output shaft of the 3.96 mm that 'buggers' it up...that shaft diameter is designed for helicopters who use the different size pitch..I have no idea why..it seems waste of time to me
IF you reduce the output shaft to the 3.2.mm or the 2.3 mm then you CAN easily buy the 46 tooth pitch that you need to mesh into the Heng LOng gearboxes and the unit will bolt right in with some trial fitting and a couple of mounting holes drilled in the gearbox side plate....It might literally be able to use the original engine mount holes.

ONCE you have turned down the shaft the gearboxes ARE great...you have NOT wasted money..they just need work. The clearance issue that I encountered on the Panzer III is VERY unlikely to bother a Tiger 1 due to the differences in hull height.
I am sorry if I did not make myself clear there.......the ONLY problem is the output shaft diameter being too large....other than that they are a great little gearbox.
Regards,
Alb

[SovereignZuul]

Okay, cool. Still put it aside for now, until I am ready to start working on my Panzer IV. The Tiger is getting a lot done right now, no workspace for awhile. Once I'm done with that tank I'll get those gearboxes fitted to my old HL zinc gears for the PZIV.