ways to improve linearity at low speed
 

Hi
Love my henglong tank from outside, but power system seems not to the hobby level.
The tank would not slowly move, it either stuck there or suddenly jerk forward, especially when doing pivot spin in rough terrain - I guess everyone feel the needs to update this part.

How are following measures doing to improve the linearity, especially in low speed scenario.
1, upgrade motor to high speed/high torque 395s, straight swap, improve speed, slightly add some torque too.
2, upgrade to 12v toss in hobby level ESC, and receiver. add power.
3, upgrade to 540 motor, and add some gear structure.
I don't know if there are kits for easy conversion, but 540 offer bigger power and higher torque, logically it is the best solution to solve problem for both high and low speed..
4, change all bearing in side out.
5, use reduced rpm 370 motor, which kills high speed in exchange of linearity, I guess it is the last resort.

All of those measures are either add torque or power to the system, logically they are all correct to do, my question which one is a best / easy to achieve our goal.

The problem may not be the power, but the control system being used. Upgrade to a control board that can use a hobby grade radio, or an add on board to the RX18 board to allow you to use one. You could upgrade to 400 or 480 motors for more torque also, but may not fix your problem as well as the control upgrade.

Herman

It's a combination of electronics, drivetrain and weight. Most of us take out the stock electronics and run third party control boards like the Clark TK-22 for example. I run the TK-22 on my WSN T-34 and I get very good control at low speeds, this is due to the quality of the electronics and the added momentum feature that eliminates the jerky low speed start. However, part of the reason why the tank runs so smooth is because I'm running a stock chassis: WSN gearbox with plastic gears, plastic tracks and plastic lower hull. Overall my T-34 weights less than my Panzer III believe or not.

I also run the TK-22 on my Panther, which has metal wheels, metal tracks, and a heavier speaker. In this case the low speed performance is not as good as the T-34, due to the added weight of the metal parts and also because I'm running the stock HL pot metal gearbox with stock motors. With heavier tanks the high torque motors and gearboxes are crucial. A popular upgrade are the 4:1 steel gear gearboxes with black 400/480 motors, HL and Taigen both make them with bearings as well.

Adding 540 motors would involve modifying the existing gearbox, I have seen it done as well.

Just changing to the 4 shaft gearboxes will greatly improve low speed performance.

Thanks everyone for your reply, I bought a 4ch ESC on route already, so I can throw out Rx18 and have a full hobby level control.
What about the 3:1 and 4:1 gearbox? are they full bearing? Given the noise level of stick gearbox, I think their mesh is probably quite bad.

The newer 3:1 and 4:1 geaboxes by Taigen and HL all come with bearings (there was another thread about these late last week). It seems that the quality of these are a lot better than the old non-bearing ones. You'll always have noise when gears are involved, it's unavoidable. The bearings and the construction of the newer gearboxes improve the gear mesh by a lot I believe.

Yes the newest gearboxes will be available soon. The gears are now shimmed amazingly on the newest steel gearboxes. That was one of the big gripes I had was the shimming. I would also suggest checking into BaneBots motors. They are super cheap and super strong. They have a decent selection and the KV rating is pretty low, allowing for a decent torque upgrade with little to no modification (just need a new pinion gear for it). If you already got a 4n1 ESC I would look at some 28mm brushless motors with no more than 1000kv. I tried brushless myself with only 1400kv and it was WAY too fast. I also tried dual 3650 motors (540) but ended up doing a lot of modifications to it for something I could of got out of a well selected 28mm motor with no mods. I would go with a new 4:1 gearbox first which will increase the amount of torque and slow speed control you have. Next check at a new motherboard or control system. Recently HL took a step backwards with their boards and made some 3 speed motherboards instead of proportional. Then after you acquire a hobby grade system you can then overshoot for power and speed and use your transmitter endpoints to slow the tank down to a reasonable speed and use your RX expo for a correct throttle response (no jackrabbit burn out starts).

Come back report my result.

Yes it is a problem of a combination of drive train, power/torque and electronic.

Now I updated to an integrated 4ch ESC, and a hobby level receiver, the start up is much smoother.
(Nobody understand how henglong's claimed a 8-bit speed control is such bad (assuming 256 levels).

But anyway, HL stuff is out, noticed one more thing: My right drive is much stickier than my left. It was noticed before, but with henglong's not-so-accurate control, it was not obvious. But now, I can clearly see right side is always a few clicks slower than left side, forward or reverse. I saw the gear box on right have metal debris and on the left only have oil.

I am guessing, pls confirm me with your experience, since the two side are different built, the variance should be a systematic variance, i,e, everyone must have right side with same issue, and then aftermarket gearbox is the only solution then.

You do also realize that without any other electronics that now you have no turret control or gun functions, correct? What do you intend to do about this?

it is a 4ch ESC, as I wrote, actually it has a switch channel for gun too.

Hi Captain Nemo12:

Not trying to hijack modeleyrang's post, but could you please let us know what's involved in installing the TK-22 board in the WSN T-34. Perhaps in a new post. I have the WSN Tiger which I assume is the same functionally. I think a lot of others would be interested as well.

Thanks,
Old Fatman

Old Fatman,

I wrote a tutorial on how to set up the TK-22 when I did my Panther build, you can find it here:

http://www.rcuniverse.com/forum/rc-t...l#post11579739

The tutorial continues on page 2. With the WSN T-34, you'll only have the cables for the gearboxes, which have plugs that are compatible with the TK-22. For the rest of the cables, I recommend you get the complete HL cable set from Immortal Hobbies, or use existing cables from a spare HL tank.

Hope this helps!

Hi Captain Nemo12:

Thanks for the information. Great tutorial.

I know the WSN :(Trumpeter) T-34 and Tiger get bad raps for durability and control, but as low cost, lightly used carpet crawlers
they fill a need for those on a budget. High speed and controllability is a problem with them and you tutorial addresses those issues.

Good information and very clearly presented. Again Thanks.

Cheers,
Old Fatman

No problem! I found that the WSN T-34 is a great indoor/carpet runner, I also reinforced the chassis with an additional ABS plate in the tub. Even with the addition of a bigger speaker, the tanks is very light. I have no problems doing low speed turns (with the TK-22 installed that is). I wouldn't recommend running the stock suspension in soft snow, the ice and snow tends to accumulate between the wheels and sprockets, and because of the fixed length of the tracks, I actually snapped off one of the idlers once.

My right hand side of gear is finally dead. after one month use, and couple of hour on 3s lipo, now it is over.
quite a few metal debris, and the gear rod is clearly wobble, sometime it stucks, sometime run.
It was sticky at beginning, now need advise to buy more robust gearbox, and hopefully hi-torque motor and whole bearing set.

Were you using the pot-metal (silver) gears? I would recommend swapping them out for black steel gears.

I want to get the ultimate version 2 gear box with hi torque motor, after some home work just now. I need Med-Low, long shaft type.
It seems there is very few vendor carry just that type.

I truly want to upgrade to ultimate verison, I believer the pot-metal gear is dead not only because of the gear itself loose true, but the brass washer loose true too. There is too much to upgrade in henglong, everything except the hull is in list of changing, so let's get done in one shot.

give Eric a shot at Imex taigen (imex erik) he has the gears you need.

I've tried looking for the Ultimate Edition II gearbox as well but they're really hard to come by outside of China. You can try ordering from Taobao, there are some sellers there that offer it and I believe they ship internationally as well. I found them for sale at HobbyRaw and bought a set for my M60:

http://www.hobbyraw.com/itemList.jsp?pgid=29&cid=20

I don't see much difference between these and the Ultimate Edition II, aside from the anodized casing and different motor colour. However, for a WWII tank you may consider using a 4:1 gearbox, the ones at HobbyRaw look like the standard 3:1 black steel ones but with bearings and stronger motors added.

I got the Ultimate Edition II gearbox now, here is my little review:
* They are well made, with clean steel gear and all bearing, chromed metal plate, etc;
* They are smoother than pot-metal ones, after I dis-engaged the motor, I can feel the gear box is really spinning well.
They worth the price, even you have to buy it off TAOBAO - the Chinese version of ebay, and shipped it over from a third party dealer - TAOBAO seller don't speak English, and never ship over sea.

They improved linearity a lot but not to the degree of realistic smooth -- I am very picky here, it is actually acceptable job for sure.

A further thought is the tank itself, Henglong hull and wheel can be bent, untrue, wobble, tweaked easily with some force on them, misalignment adds friction.
Gear box is also a problem, i my opinion, there are too many level of gears, and the small gear won't have the required accuracy. It is better off to use 540 motor to begin with, and using only worm gear for maybe a couple of level of reduction. I will certainly try Tamiya style gearbox in my next project,

The last edit is: If you can't get the ultimate version, you can get a steel version. A chinese forum post an innovative mod, using drill chuck to hold the gear axial, take it as a lathe, and grind it down from 3.5mm to 3mm contact, then replace brass bearing with the flaged ball bearing. It is not too hard to grind off only 0.25mm radial.