ArkModel piston tank wiring

[hobbytrax]

Hello,
Really stuck with this one. I've been tasked with building the dive tube for an ArkModel submarine, something I have never done before however...
I've got everything on the RC side working but the piston tank refuses to move at all when connected to the Ballast Tank Control Unit (BCU)
The piston tank is supplied pre-wired with three microswitches and a motor, but when I compare the actual wiring wiring to that on the diagram, the motor is connected the other way round.
I did find a post on here from a couple of years back where someone had the exact same problem and concluded BOTH the diagram and the supplied wiring was wrong, but didn't say what is the right answer. I'm hoping someone can help me.
Interestingly I removed the wiring from the motor and applied 12VDC direct to the motor. This moved the piston rod but NOT the pilot shaft (I was trying to understand how the microswitches worked but this has confused me even more!) I've seen generic wiring diagrams showing 2 or 4 microswitches, but never one that's got only 3. I assumed both piston rod and pilot shaft would move together but they don't seem to.
I've been onto ArkModel who asked for a video, however when I tried it again this morning the motor seems seized and I can't get it to move in either direction.
Can someone explain how the motor and microswitches should be wired and when the pilot shaft should move?
I've attached a couple of photo's
Many thanks!
Trevor.

[type7]

Take the piston tank apart first. Mine had a very viscous grease in it that really strained the motor and has to be removed to have any chance of it working. In addition, the piston face and tank end plate are very flat so the piston gets stuck at the end of travel. A very poor design. I tried 2 of them and gave up on them entirely. Besides they are too small for the subs they were in to have reasonable dive performance.

[Subculture]

I see from your post the tank operates well mechanically, so it doesn't sound from your description like it's binding up.

The electrical side looks like a reverse-engineered single channel Engel TAES, which also uses three microswitches per tank. The diagram you posted looks correct from what I can see. Can't tell what the wiring is like from the rats nest shown in the second picture, but I would suggest testing each part in isolation, e.g. test the output of the board- M1 and M2 on the board should slot a high side feed depending which way the tank is instructed to drive, with common to ground.

The three microswitches work to limit the motion, the two grey switches on the diagram limit the tank motion for empty and full, the red microswitch is for neutral trim, or just slightly positive buoyancy, and it should connect to the control board microcontroller.

[hobbytrax]

Thanks,
Yes I was suspecting the piston had got stuck as one end and will try and free it off.
Can you confirm how the pilot shaft and piston rod are supposed to move together? When I did have the piston moving the pilot shaft didn't seem to move at all. Does it only move when the piston is at it's maximum?
Trevor.

[Subculture]

Haven't got one of those Ark Model tanks, but I suspect it works very similarly to the Engel tanks. The pilot shaft on the Engel tanks is basically a spring loaded plunger, which will start moving once the tank gets near the end of a filling cycle. I would expect the red limit switch to actuate first where the boat will be slightly positive or neutrally buoyant, then to fully flood the tank and bottom the boat the grey limit switch is then actuated at the end point.

Perhaps the limit switches need a bit of adjustment/shimming, you want them to actuate before the tank hits its mechanical limits. Also should check to see the microswitches are in good order, which is relatively easy to do with a multimeter.

[hobbytrax]

Thank you.
I've managed to get it to move forwards now. It seems it was stuck at one end. I did this by applying 12VDC direct to the motor.
Frustratingly I've discovered the piston moves much further forward than I expected and it's hitting where the batteries are fitted meaning we're going to have to move them.
And yes the pilot shaft moves on a spring when the piston it almost at the end of it's travel.
I've gone through the microswitches and have a proper circuit diagram of how these work and they seem fine.
I've measured the outputs of M1 and M2 and I'm always only getting 12V at M1, never anything else. I've changed RC channels and it's just the same.
I've checked the microswitches and they are fine too.
Finally I tried the motor connections both the way it's supplied and the way it's shown in the diagrams... no difference!
No matter what I do the piston tank won't move under RC control.
If anyone's got one wired up and can confirm how it's wired that would help.
Regards,
Trevor.

[TuptubBuilder]

Hi Trevor,
First, and most importantly, I hope you have added a fuse to the positive post of the battery. I have recently revisited my Arkmodel WTC that I gave up on four years ago. Back then I wired the ballast switch according to the Arkmodel diagram and it worked. However, the first time I left the piston in mid stroke it shorted out and blew the fuse upon power up. I assumed that the switch outputs power up in an indeterminate state. So as long as the piston position is at either end it’s good to go.
Given the problems I had the first time around, I have decided to replace the Arkmodel switch with the Alexander Engel Ballast Tank Switch “UNI 12V”. I hesitate to recommend it since it’s on its way and I haven’t received it yet. It costs about 60 USD.
I also had an EMAX servo fail almost immediately. I have replaced them all with all metal HiTecs (HS-82MG). Another issue (deal breaker) was the development of stress cracks in the stern Injection molded end cap. They developed around the control rod bushings and motors. Also, the motor shafts measure 2.3 mm in diameter but the cup seals have a 2 mm ID. I’m rebuilding the stern with 3D printed parts to remedy the Arkmodel shortcomings.

[hobbytrax]

Hi TuptubBuilder!
Yes we did put a fuse in the battery line, not sure that would have done much good if the piston rod had screwed itself right through the batteries! They are fitted in the place they are supposed to go, but no-one tells you the piston rod runs right through that space!
I agree with you the WTC does have a lot of shortcomings. My friend started this build and passed it on to me to finish, I've plenty of experience of electronics but no experience in RC subs!
We have the stress cracks around the end caps too. I've run poly cement over the cracks, not sure if that's going to hold though.
I think the biggest problem is it's just not serviceable once you've got both end caps on. It's such a job to take it apart even to charge the batteries, let alone the work involved with removing it from the sub in the first place - it's crazy!
I do know a few people produce a full replacement WTC for this sub. My friend suggested I produce a kit of extra parts to fix some of the problems, along with some proper build instructions however I'm not sure I have the time nor is there the market for it.
I haven't got much further with progress. I've got it freed off the end (yes it had just got stuck) but I still can't get any life out of it under RC. I know the receiver and wiring to the BTU is good but I only ever get M1 high no matter what I do. I think I have two problems here (at least!) firstly the BCU isn't responding to the RC and second the wiring on the tank isn't right. I'll investigate the ballast tank you have ordered, I might give it a go.
I've asked about the position of the links on the BCU board to ArkModel. The manual doesn't really make it clear what they do.
Thanks for your comments on the motor shaft diameters. That explains another little problem I was seeing. The motors are running fast in one direction, but much slower in the other. I was also seeing a little smoke from the bearings. I had suspected it was just a tight fit and was "wearing in" but hadn't investigated further. I might see if I can enlarge the hole slightly without it letting water in.
Trevor.

[Subculture]

The issue with the ballast tank control board could be down to many things, but the most likely contender will be a faulty/stuck relay.