RE: Heavy Metal Mato - Stage 1

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RE: Heavy Metal Mato - Stage 1 - 2/22/2012 5:23 AM

shambrick

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>...and I can see the antenna wire snapping easily.
LOL, I just extended my antenna wire about two hours ago for that very reason :-)

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RE: Heavy Metal Mato - Stage 1 - 2/22/2012 6:53 AM

rampa203

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I've read that metal and carbon fiber models need to have external antennas. Did you solder a new one to the RX-18, or did you do some kind of a splice? With mine (2.4 GHz) the actual antenna has to stay about 32mm long, so to get it outside you have to lengthen the coax that leads up to the antenna. Apparently the only way to do it is to solder an entirely new antenna onto the receiver pcb, which has very tiny surface mount soldering requiring some skill to do successfully - skill I don't have. So this is why I was dreading it so much, and why I am so happy that maybe I don't need to do it after all, according to rivitcounter. I hope we are talking about the same kind of metal.

Russ

quote:

ORIGINAL: shambrick

>...and I can see the antenna wire snapping easily.
LOL, I just extended my antenna wire about two hours ago for that very reason :-)

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RE: Heavy Metal Mato - Stage 1 - 2/22/2012 4:43 PM

shambrick

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I'm using an RX-18 set up so I just extended the wire a few inches on the top hull antenna mount side. The stock set-up has a male-female connect in the middle that's easily detached.

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RE: Heavy Metal Mato - Stage 1 - 2/22/2012 9:22 PM

rampa203

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Some Improvements to the Gearbox and the Gearbox Mount

As I stated earlier, I broke one of the Mato 2.0 Gearboxes that came with the Mato metal tank. Well I had a backup set of Mato gearboxes, and I'm going to try them again with a few preliminary differences. Per Dan's suggestion of using emery cloth on the gear axles I did something similar. I put the axle in the chuck of my dremel and applied a 1500 grit abrasive pad for just a few seconds, which removes the oxidized layer of metal and produces a miniscule reduction in diameter. This is to prevent the gears from binding on the axles. I lubed everything with Finish Line Extreme Fluoro grease and used blue threadlock on the gearbox side screws and the pinion set screw. I didn't do any of this before except the lube. Also I am going to break-in the gearboxes properly, which I also hadn't done. The first time out I had gone strait to an extreme torque test, without doing any normal maneuvering first, and this is when the gearbox broke.

On to the gearbox mounts - my tank had some major flaws from the factory, and I'm going to assume that other Mato metal tanks have the same issues. Really there are four main problems 1) the mounting plate was warped (wasn't flat) because of some protruding metal, as I mentioned before. That was easy to fix with some filing. 2) The gearbox was held to the mounting plate by only two screws, both in the centerline of the gearbox. This allows for rocking movement along the long axis of the gearbox. We all know that you need a minimum of three fixation points to hold an object in a fixed position in space. 3) The mounting plate is only 1 mm thick and its flexible - the gearbox is not directly connected to the hull of the tank, rather it is "floating" on this thin metal plate. 4) The two mounting screws are anchored to a very shallow thread - not getting much bite in this thin metal. Also they are easily stripped - I've done it!

Here's what I did about it - I decided I wanted to fix the gearbox directly to the hull of the tank. The hole in the mounting plate that I had previously filed does line up with a hole in the gearbox. However the existing holes in the hull standoff did not line up with the hole in the mounting plate. So, using the mounting plate as a template, I drilled new holes all the way through the standoff, the hull itself and out the bottom of the tank. I then tapped the hole to 3mm thread - see images. I could then use a long screw to go through the gearbox, mounting plate and all the way through the hull. It turned out that 12mm is the perfect length to do this, leaving the end of the screw perfectly flush with the bottom of the tank when it is fully tightened. I just got lucky with that, and so there is no protrusion below the tank that could catch on terrain. The thickness of the gearbox lower plate and the mounting plate together is about 2.5 mm, so this screw is getting fully 10.5 mm of thread bite - thats incredibly strong. Also I'm using hex socket stainless steel screws, which are much stronger than the stock screws.

Now the gearbox is anchored at three points with direct fixation the the cast metal hull. The gearboxes are siting flat the way they should be, and my motors are now parallel to each other. Before, with the warped mounting plate, the motors were touching each other at a funny angle. Maybe all these problems contributed to the breakage of the first gearbox - I hope so.

Next step is breaking in the gearboxes, then it will be time for another field test - this time with more conservative goals in mind.

Thanks for reading,

Russ

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RE: Heavy Metal Mato - Stage 1 - 2/23/2012 3:27 AM

rampa203

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Another Thing to Protect the Gearbox

It was suggested that the instant high torque that brushless motors can produce may have been a factor in the failure of my first gearbox. You can reduce this instant torque by programing the ESC to slow down the acceleration of the motor. See the picture below - You simply connect the servo lead from the ESC to the programing card, and then turn the battery power on to the ESC. The programable parameters are 1) Reverse Power - I chose the low setting so that the tank will be slower in reverse, which was the case for the real Tiger tank. 2) Start Power - this is the acceleration setting of the motor that I mentioned. I chose the low setting, which should apply power more gradually than it did before. 3) Drag Brake - This is active breaking by the motor when the throttle is at neutral. I chose high so that the tank will break on a hill if I stop. 4) Battery type - I chose 3S Lipo.

I hope the reduced acceleration helps.

Russ

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RE: Heavy Metal Mato - Stage 1 - 2/23/2012 4:04 AM

Panther G

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Just a quick question, dont you guys run those Lipo sacks in your models when they are running besides charging?

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RE: Heavy Metal Mato - Stage 1 - 2/23/2012 7:18 AM

rampa203

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I'm sorry, I don't understand your question.

Russ

quote:

ORIGINAL: Panther G

Just a quick question, dont you guys run those Lipo sacks in your models when they are running besides charging?

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RE: Heavy Metal Mato - Stage 1 - 2/23/2012 1:06 PM

STO_118

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Odd hearing about all these stripped screws, I've never stripped a Heng Long screw, I have stripped out the plastic posts but that isn't really surprising.

The only real damage I've seen to the V2 gearboxes was a sheared drive axle, the mounting plates are a weak link although the ones I've checked here are all OK.

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RE: Heavy Metal Mato - Stage 1 - 2/23/2012 2:31 PM

shambrick

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I believe he means the lipo safe charging bags that you're supposed to use while charging - to keep your house from burning down when a bad lip decides to go "poof"! The answer is "no", I think it's only required during charging - I've never heard tale of anyone using one while running.

quote:

ORIGINAL: rampa203

I'm sorry, I don't understand your question.

Russ

quote:

ORIGINAL: Panther G

Just a quick question, dont you guys run those Lipo sacks in your models when they are running besides charging?

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RE: Heavy Metal Mato - Stage 1 - 2/23/2012 2:51 PM

shambrick

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Thanks a ton Russ!

I had not planned on tearing my sample down to this extent, but I guess it's worth it to make it propper. I guess I'll be hitting up Habor Freight this WE for a tap set :-) !

Sheldon

quote:

ORIGINAL: rampa203

Some Improvements to the Gearbox and the Gearbox Mount

........
Thanks for reading,

Russ

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RE: Heavy Metal Mato - Stage 1 - 2/24/2012 6:13 AM

shambrick

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Funny...I just took my new Stug III apart for painting, and now see that I'll have to do the same fix as below due to cracked plastic gearbox mounting stubs! The things were basically floating in there! Gotta luv these things!!! :-)

quote:

ORIGINAL: rampa203

Here's what I did about it - I decided I wanted to fix the gearbox directly to the hull of the tank. ...

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RE: Heavy Metal Mato - Stage 1 - 2/24/2012 8:19 AM

Panther G

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This is ****. Before you can make a quick 2 minute reply the server times out. **** I am surely fed up with this circus of a forum

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RE: Heavy Metal Mato - Stage 1 - 2/25/2012 11:01 PM

rampa203

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Battery Charger for High Capacity Dual Pack

I have a Bantam BC6DX-II charger which I really love. It is 50 watts which is pretty standard for this size charger. However if you have higher voltage high-capacity batteries, for example 3S 5000 mAh, 50 watts is not enough power to charge even at 1C. For this example 11.6 V (3S) and 5 amps (1C charge) is greater than 50 watts. So the charger will charge at less than 5 amps. To add insult to injury, many lipo packs are capable of being charged at rates quite a bit higher than 1C, 6 - 8C for example. My point is that a 50 watt charger really is not adequates for these larger batteries. And what if you are using two dual batteries like I am ?

Here's the Solution. Turnigy Mega 200W x 2 charger and HobbyKing 540W power supply. It has two seperate charging circuits, each 200 watts (400 watts total.) You can charge two batteries simultaneously at up to 200 watts each. It seems to work great, and the total package (charger and power supply) were not much more money than my Bantam charger. But that's HobbyKing for you - they always have things at unheard of prices.

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RE: Heavy Metal Mato - Stage 1 - 2/28/2012 2:56 AM

rampa203

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Servo Gun Elevation

I don't have self-centering up and down on the left stick of the transmitter beacause it is actually an airplane/heli transmitter and the left stick up and down is for the throttle, which you don't want to be self-centering. This is the channel I want to use for gun elevation, so the gun will just stay in the position you leave the stick. (As opposed to the Heng Long transmitter where the stick position tells the turret to move up or down, but it doesn't determine the final elevation.) To do this you need servo control of gun elevation, and that's what I decided to do.

To access the gun you have to remove the retention plate holding the turret to the upper hull, remove the bottom of the turret and then remove the small wings that holds the gun in a fixed position. You then have to attach the airsoft unit from the Heng Long donor tank - this is the part that allows the gun to hinge inside the turret.

I decided to mount the servo under the hatch with the screw holes. This way I didn't have to drill new holes in the tank and the screws were concealed under the hatch. I made a bracket for the servo to be mounted here. I also made a bracket for the back of the airsoft unit to attach the ball-link from the servo. After these where attached, the ball-link connector was attached to the servo and the airsoft bracket. Because of bracket and the ball-link connector extend below the turret as the gun is elevated, I had to modify the hole in the floor of the turret, which I did with a dremel. I then reattached the floor to the turret.

I tested the system with the radio, and the gun moves up and down as expected although the range of travel might be reduced a little. I think I might need a longer servo horn to get a little higher elevation on the gun.

Russ

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RE: Heavy Metal Mato - Stage 1 - 3/6/2012 7:01 PM

rampa203

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GUN AND TURRET

I replaced the turret elevation servo arm with a longer one and it made a small difference. I think I was almost at the limits of the gun movement with the smaller arm - the gun really doesn't move very much. Seems like its moving more when it moves slowly. I wonder how it compares to the real Tiger I?

For the turret I harvested the large gear and the motor/gear unit from another tank. But the gear would not fit in the hole in the upper hull. You can see in the pictures below there is excess metal (maybe you would call this flash) on the inside lip of the hole preventing the gear from sliding in. I ground this down with a dremel, after which, the gear fit perfectly.

On the motor/gear unit the motor itself seemed to rotate some. Also there were some solder connections on the underside that would be perilously close, if not touching, the metal hull. So I applied some foam tape as an insulator and also to help stabilize the motor. I used longer bolts to fix the motor/gear unit to the hull. By the way, you need to stock up on 3 mm screws before you do this. The original screws that went into plastic obviously won't work.

To control the turret motor I decided to use a brushed motor speed controller. It has to be an ESC designed for cars so that it has both forward and reverse. I'm using one that I bought on ebay (shipped from China) that I think was $12 including shipping.

The final question is what voltage to the turret motor. I probably should have measured what the RX-18 actually puts out. Since the NiMH stock battery is 7.2 volts I assumed that was it, but it could be lower. My battery voltage on this tank is 12.6 (3S) and I know that is too high, so I used a 7.2 V 4.5 amp BEC. The power is tapped off the first connection of both batteries, before the main speed controllers for the tank.

If you look at the video you can see that the gun elevation is not perfectly smooth and it needs to be slower. I think a servo delay unit would help here. One nice thing about this setup is that you never have to wait to go through the whole up/down cycle like on the stock Heng Long. Also you can tell exactly what position the gun is in by the position of the stick (on my radio the stick is not self-centering in this direction.) Regarding the turret I am pretty happy. A nice feature is that it is proportional, so that you can rotate faster or slower. Slow rotation might be nice for fine-tuning aim. It might not be historically accurate though.

Picture upload doesn't seem to be working

http://www.youtube.com/watch?v=ekcZfxz9_f0

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RE: Heavy Metal Mato - Stage 1 - 3/6/2012 7:02 PM

rampa203

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RE: Heavy Metal Mato - Stage 1 - 3/6/2012 10:24 PM

rampa203

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I think it worked this time

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RE: Heavy Metal Mato - Stage 1 - 3/8/2012 6:40 PM

rampa203

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Changes to Gun Servo (Again)

The longer servo arm was really a bit too long - I had to cut my servo travel end-points to about 50% in both directions to prevent binding of the servo. I was thinking that this might cut down the resolution of the gun movement. Also, the increased torque on the servo caused by the longer arm might be making the elevation less smooth. Anyway, I decided to try the smaller servo arm again with a couple of changes, and I think it's better.

1) I moved the ball link attachment to the airsoft bracket to get more elevation. It's just a few mms but it helps.

2) In the radio settings I changed the servo travel endpoints to 120% in both directions

With these changes I'm getting full travel of the gun. I think I'm probably getting the full resolution of the servo also, and the movement of the gun seems a bit smoother, but not perfect.

I'm going to order some of these delay units http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8863 as soon as I have a big enough order to justify the shipping charge. I think that will help. There is something called "THRODELAY" on my radio, which I assume means throttle delay because it seems to work on the throttle channel (which on my tank is the gun elevation channel.) It does slow the servo, but the gun goes only to the highest and lowest positions, nothing inbetween. So that won't be helpful.

Russ

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RE: Heavy Metal Mato - Stage 1 - 10/28/2012 10:58 AM

trencha

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hi all, i have two questions about the mato lower hull and the screws for fix the idle wheels..
ok, i got the the mato lower hull but i didnt get the part for close/snap with the mato upper hull
,i would like to know the dimensions of the 2 little rectangular parts(fixed to hull by screws)
so i can make them by myself
http://imageshack.us/photo/my-images/841/matolowhull.png/

plus i got the metal idle wheels with relative screws but the screws came like a nail without screw thread so i cant fix them to the lower hull, any solutions or does someone knows the exact dimensions of the screws?

thankyou in advance and sorry for my bad english

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