StuG III 014 - A Team Effort

[Darren_Hagarty]

Motion Kit Setup - Channel 5 for Amplifier
Hi Adrian,
Transmitter is a Futaba T8J. I'm aware Amortek only test with a Futaba 7C (FAST) however they weren't available in Oz. I've done some reading on the Futaba manual which is heavy going as all examples relate to helos or planes.
Anyway I worked out that the photos showing the default controls for each channel were a red herring. What I thought was channel 5 wasn't. Turns out the photos showed the default layout for a 8JA Mode 2 whereas mine was a 8JA Mode 1. The giveaway was one line that mentioned where one particular spring loaded switch was that highlighted mine must be a 8JA Mode 1.
Anyway I changed channel 5 to be the three way switch that I wanted and re-ran the Amplifier setup. This time it worked as expected, at turn on with the switch in the centre position no engine noise. Moving the switch forward starts the engine and switching back to centre sets to run in proportional mode. A flick forward turns off the engine as expected. I haven't tried the other sounds yet.
Based on this success I now want to mount the motors and try running with the fighting compartment and rear deck off.
I expect the gun setup will be fiddly so want to test the tank running while I have a few days off then come back to the gun motion.
What is best practise when mounting the motors should I use some dry lube or grease or nothing?

[Stephen White]

Darren

Mark recommends avoiding grease which can attract abrasive particles. Either assemble it dry or you can use a dry film molybdenum lubricant such as Rocol Oxylube:

http://www.rocol.com/products/inorganic-dry-moly-spray

I use it on all moving parts and it works well.

Stephen

[Adrian Harris]

Good to hear the sound is working now.

I will second Stephen's recommendation of a dry lube.

In dry conditions it's amazing how much dust and sand gets inside these machines, after being stirred up by the tracks, and the grease will become its final resting place.

Adrian.

[Darren_Hagarty]

Thanks Stephen and Adrian I'll see if I can get some dry lube and have a go at mounting these drive motors.

[Darren_Hagarty]

Motion Kit Setup - Drive Motors
We struck a problem straight up when we found the flanges for the drive motors needed a particular alignment. They can go in four ways but only one is correct. Unfortunately we didn't look too closely to the photo in the guide that showed the correct alignment.

We had to drop the tracks, remove the drive sprocket, bush, and gearbox mounting on both sides, and refit the drive flanges correctly. At this stage we tried the drive motors and found that on one side the end of the drive shaft just wouldn't go through the hole in the hull. We filed the hole out until it did. Then refitted the gearbox mounting, drive sprocket and bush.

We left the tracks off as we wanted the test the drive motors.
So about three hours later we were back to fitting the drive motors which went on OK.
We found we could manually with a fair effort move the drive sprockets back and forth which gave us confidence that the gears had engaged ok.

Next we connected the Power Supply, Speed Control module, and Amplifier module loosely in and around the hull. With power on, the drive sprockets seemed to turn OK. Of course we had to reverse the blue and yellow wires on the drive motors to get the motors spinning forwards when pushing forwards on the throttle joysticks. Interesting they made a slightly different noise running backwards verses forwards. The father in law who was visiting said it was something to do with the gearbox running in reverse.

We've also cut the false floor plate about 30cm from the front so its in two pieces. The idea being its easier to fit separately than together. We also had to cut some notches in the sides of the plates to allow it to drop over some nuts on the inside of the hull.
To make it easier to remove the rear plate (about 45cm long) we cut some notches in the centre of each end to allow fingers to fit through and that seemed to work OK.

In the motion kit guide it suggests mounting the power supply module at the very rear of the hull on a purpose built bracket which seems like a good idea however a quick check indicated the power cable to the Speed Control Module would be too short. So now we'll have to try some different arrangements of the modules to see what's neatest.

[Darren_Hagarty]

Motion Kit Layout - Modules Mounted on False Floor

We're happy with the false floor being cut into 40% /60% with the 40% piece being at the front under the drive motors. The 60% piece for the rear has handy notches cut for fingers to allow easier removal. We used Velcro tabs to secure the rear plate but not the front as that would make it harder to get out and the rear plate secures it from moving anyway.

The Speed Control Module is between the drive motors. The Power Supply module is further forward than we'd like at the moment however that to allow the Amplifier Model to be mounted behind it. Originally we had the Amplifier Module centred on the left hand side of the hull however we found that the fighting compartment hangs over about 1 inch from the hull side and tends to swash down on the cables coming out of the Amplifier Module. The Power Supply Module being shorter is not affected the same way.

Also again for height reasons we've pushed the batteries as far to the rear as they can go as the fighting compartment sits lower than the batteries even when on their side.

The Battery move rear meant that both speakers ended up in the centre of the hull. Initially we had one to the rear. The RC Receiver is mounted on the rear of the hull.
At this stage the Auxiliary Module for the gun recoil/slew etc. is planned for the left hand side of the hull but we've left that for the time being. At this stage we don't plan to install the smoke unit as we may not have the room.

Anyway onto the first drive test.
With the hull now weighing over 60Kg moving it outside is more of an effort as Penny can hold up her end but only just for short distances. We'll have to get one of those scissor lifts.
A run in the backyard worked OK with no broken track pins and was a good exercise in leaning to steer it around. We noticed an unusual intermittent noise when running which appeared to be coming from the drive motors. (PM us for the sound recording as .m4a attachments aren't allowed) We later worked out the noise came from both motors and in fact each had a slightly different pitch.

We tried tightening the grub screws in the drive sprocket bushes, running with the hubcaps removed, running with one extra track link however none made a difference.
When testing with the hull on blocks we could run at full speed both forward and reverse for extended times with no intermittent noise. Interestingly when running a track turn with one throttle stopped we don’t get the noise when either track is stopped. Speed is low though.
Battery voltage was showing as 26V. We felt that we could feel a slight vibration when the noise occurs on the flange end of the drive motor.

[Darren_Hagarty]

Hull running tests




We’ve pulled the drive sprockets off and the gearboxes.
We found some scuffing on the inside of the gearbox housing where the driveshaft sprocket meshes. It was worse on one side compared to the other.

We used a dremel to buff out the inside of the gearbox housing to hopefully reduce that friction as a noise source.The drive motor that was causing the most scuffing was also slightly different to the other drive motor.
The gear on the end of the drive shaft was hanging over the drive shaft about 1.5mm which doesn’t sound much but is noticeable and probably explains the worse scuffing on that side.

We also reamed out the hole in the hull where the drive shaft passes. It was very tight on both sides with only the width of a piece of paper between the edge of the gear and the hull. Possibly with vibration it could touch.
It was noticed that the gear doesn’t completely pass through the hull but we guess that’s how it’s meant to be.

We’ve used some Rocol Lubricant as suggested on the gearbox and the end of the drive shaft, it was what we considered a light spray.

We’ve created two YouTube videos of the hull running one on blocks and the second running on the grass both forward and reverse and also doing track turns.

The intermittent noises are still there, the work we did didn’t seem to make much difference.

The noise appears to have a different note from the left and right motors and can come from either motor or not at all at times. We haven’t noticed the noise when doing a track turn. The noise never occurs when on blocks.

We tried shaking the hull when on blocks but couldn’t induce the noise. We also used two straw brooms to apply pressure to the drive sprockets while they were turning to simulate load when on blocks but again couldn’t induce the noise.

There doesn’t appear to be any contact with the tracks on the mudguards or hull.

If you haven’t got any suggestions please let us know. We have shown Mark the videos but he hasn't heard that noise before.

[Adrian Harris]

Takes me back to my old Ford Escort Mk II when the differential wore out.

From the frequency of the sound, I would say it's coming from the EMD gearbox, rather than the final drive gears. All my tanks have had witness marks on the hull from the main sprocket drive gear, but there's nothing for the gear to hit to make such a loud and obvious noise.

Are you able to run the Stug backwards whilst someone is touching each of the motors in turn ? That amount of noise should be easily felt as vibration, and so you should be able to tell if it's just one motor or both. Sounds like one to me.

Adrian.

[Darren_Hagarty]

Hi Adrian,
Is the EMD gearbox in the drive motor?

[Derek Attree]

Hi Darren
It sits on the end of the motor and is the part that brings the motor shaft out
at right angles to the motor.


Derek

[Peter Silcock]

Darren that noise sounds very much to me like the pinion gear is catching or slipping on the shaft or there is some misalignment of the gears which is amplified when under load. Have you tried checking that all the motor mount fixing bolts are tight and that there is no movement of the motors when under load? Even a tiny amount of movement may cause the gears to catch or slip if as you say there is only minimal clearance for the gears. The other thing you might try is realigning the motors to see if the noise changes. If you are satisfied that everything is tight and correctly aligned and that there is no evidence of the tracks catching on a protruding nut or bolt then it may be a problem with the gearboxes themselves. Let us know how you get on.

[Darren_Hagarty]

More Running Tests trying to debug Intermittent Noise

Hi all, it’s been a while since the last post but we’ve spent many weekend on testing behind the scenes trying to nail down this intermittent high pitched engine/gearbox noise when the hull is running.


Armortek offered to have the motors sent back for testing however we wanted to convince ourselves the issue was isolated to the motors otherwise we’d be back to square one.
We’ve reviewed all our tests and used a more regimented approach to the testing and documented results in a table only changing one item at a time and have come up with these results.

1) Tried a new radio.
The four radio units that are listed in a forum on the Armotek site haven’t been available in Australia for a couple of years or so. By doing some digging those units all used a 22ms frame rate (better suited to analog servos) and I expect the Armotek modules were designed to interact with such a signal rate. The Futaba 8J radio we had by default uses a 13ms frame rate and we couldn’t see any option to change it. Queries to Futaba support about whether it could be changed went unanswered. We checked and the closest we could get to one of the original four tested radios was a Spectrum DX7s. It by default uses a 22ms frame rate (can also be set to 11ms) and we tested at 22ms. The receiver was a 6 channel AR610.

Result:
Unfortunately the results were identical to the Futaba 8J the intermittent noise persisted. So we can probably rule out the radio as the issue. For our remaining testing we continued to use the Spectrum DX7s due to its 22ms frame rate.

2) Tried different lubricate options.
We tested with different lubricant options in the final drive case assembly which the drive sprocket sits on. We used no lubricant, Oxylube, and a generous serve of standard grease.

Result:
There was no change with the intermittent noise persisting.

3) Tried running with one engine driving and a tow rope on the non-driving side.
The non-driving motor was left connected in the back of the hull and freewheeling so it’s as close to the current load of two motors.

Result:
In this case we could only get the noise from the driving motor when going down a wheel rut hole. The noise seemed to appear as the drive sprocket hit the ground and slowed momentarily. The result was the same on both sides. We also found we could generate the noise by giving the back of the hull a shove as it was going also. It was like an engine braking effect. We also could produce the same sound when driving with both motors and giving the hull rear a shove while running. When we connected both motors back to driving we still had the intermittent noise seemingly from both motors generally at different times. It was worse going downhill which ties in with the engine braking effect. We tried wrapping one motor to deaden the sound to highlight when one was making the noise but that didn’t help.

4) We noticed one drive sprocket on the end of one motor overhung the shaft 1-2 mm

Result:
We smoothed the overhang with the dremmel and retested but it made no difference. We also noticed that the shaft had a slight wobble in it when you looked at it from the side while freewheeling but that could be normal tolerances. We found there was a couple of mm of play in the sprocket at the end of both motors. You could rock them back and forth a few mm either way. That could be normal as we have none to compare to. We also found one motor seemed to be harder to turn by hand but again without others to compare it’s hard to say if that’s significant.

5) The guide says to use about 97 track links.

Result:
We were using 91 which seems a fair difference. We tried using 92 however that was so sloppy we dropped a track off. Maybe 97 is a typo or a carryover from the panzer 3 notes where a different track link may have been used.

6) Some return rollers were not running freely

Result:
We’ve noted this before and planned to come back to them. We didn’t think it would be significant to the running of the tank maybe just use a bit more battery power. To be thorough we removed all of them in case the extra resistance was causing an issue and making the motors slip. Retesting however showed no difference and the intermittent engine/gearbox noise remained.

7) Confirm Tape Lock grub screws were tight

Result:
These sit inside the main drive sprockets we confirmed they were tight.

360 Degree turns with one motor driving

Result:
As before we cannot reproduce the noise with only one motor running

9) Running on blocks

Result:
As before we cannot reproduce the noise when running on blocks either in forward or reverse. Also ran flat out in forward and reverse.

10) Had a friend review the tests for a second opinion

Result:
Anthony is quite mechanically minded with a well-equipped workshop. He thought the tests we’d done were fair and that the noise was most likely either from the reduction gearbox on the end of the 24V motors or from the drive sprocket of the motor engaging the second reduction gearbox on the outside of the hull. On the teeth of the outside reduction gear it was hard to see a shiny mark where the teeth and been engaging. He did think that based on the frequency it was more likely the first reduction gearbox on the 24V motor itself.

Without having a bunch of spares it’s hard to eliminate causes. If we lived in the UK we would have taken the whole unit down to Armortek to see if we could eliminate the issue in one day.

There is an outside chance that the power supply module or drive motor modules could be breaking down under load. If we knew someone with a tank nearby we could eliminate those modules. It’s possible the second reduction gearbox on the outside of the hull could be an issue and that’s one item we haven’t taken apart since the initial build. It would mean that both have the same fault or incorrect assembly. Again though it’s harder to explain failure under load if it’s incorrect assembly. It’s possible that the batteries have an issue supplying current when under load. We haven’t tried another set of batteries however it all costs money and could be just like the second radio unit.
So if anyone can see any flaw in our testing or can suggest another test we’re happy to retry. At this stage we are out of ideas other that a second battery.

Also Peter Silcock mentioned a pinion gear slipping in his last post but we weren’t sure what he meant by that.

[Jeffrey Goff]

Hi Darren, it has been a while since I built a Panzer 111, but that noise does not sound like a motor or gear box problem, it sounds more like the vibration caused by the track
rubbing against the body or mud guards, turn it on its side and see if there are any witness marks
regards Jeff

[Darren_Hagarty]

Hi Jeffery,
Thanks for the reply. We have looked long and hard for any rubbing marks on the hull or mudguards however have seen none. One reason we don't also think its that is that the sound frequency would be lower due to the lower rotational speed of the tracks. For example with the return rollers off the track hangs down a bit and brushes on the top of the front and rear shock absorbers. This noise is a much lower frequency than the other noise we are chasing. Also as you accelerate the pitch goes up as you'd expect.

[Peter Silcock]

Hi Darren what a frustrating little problem to resolve. If I have read you right the noise does not occur when the motors are not under load. Wheels and rollers can make a really loud squeal if they are semi locked or if a bearing is loose and rotating in its housing. I would check these but pay particular attention to the bearings in the final drive casing.You have eliminated the possibility of the tracks rubbing on anything which only leaves a problem with the drive train itself. One thing that did strike me however is the fact that you mention that one motor is easier to turn by hand than the other. The only motors I have out of models at the moment are Tiger ones and none of these can be turned by hand at all(although I am old and feable!). Whilst I appreciate that P3 ones are different I do wonder whether there is a problem with the gearboxes in the motors themselves. The only motor I have been able to turn by hand was in a german halftrack and a plastic gear had failed. If they are Parvalux motors it might be worth speaking to them I found them incredibly helpful. Keep at it,