motor problems with 3.5 wtc 2 motor drive

[robert lipsett]

today was my first running of my uboat since I bought a bigger battery to operate the boat for longer cruises. I used to use a 3300 but have gone to using a 5000.

The boat is six feet long and ways approximately 50 pounds. it is so heavy because it originally was to have watertight compartments with a lot more air and so it needed more ballast to sink. I had many problems with leaks so I put in a wtc from caswell but I still had a lot of lead that was in the boat to help it go down. Because of this weight I have had to run the boat at 3/4 to full speed to get a good walking speed.

The props pitch has been altered to be less so that the battery would not overheat which it did on its first trial last year but since the pitch was changed I had no overheating problems with the battery. I went on my first real trial after balancing the boat and all was going very well,

My only wish is that the water I was in would have been a little clearer because it was easy to lose sight of the boat when it was under water. Now the heart of the problem, I am 15 minutes into the patrol and I surface but the boat was slow to respond so I blew the tank with the propel charge and she was fully surfaced. I tried to bring it back in but the action were hesitant. as I got closer too me i could hear the motors run for about 6 seconds then shut off for about 10 to 30 seconds. They were cycling on and off. reverse speed was almost non existent when I tried it. (this boat is so big and heavy it only turns going forward due to the props being in front of the rudders). I thought that maybe the battery had run out of power. strange since the lipo guard had not surfaced the boat or blown the tank but it might have occurred after I blew the tank???

I took it home and rinsed it off which took about 30 minutes before cracking open the wtc. the engines were fairly warm to the touch but not too hot. I tried to charge the battery but the balancer reported one cell over charged. I drained it at .85 amps and I got at least 1000 mah out before I went to bed and when I woke up the charger was reporting it timed out, if I knew how to work the charger better I could have gotten the final mah reading before it shut down but that was my fault.

I don't think the battery was too low. I am wondering if I overheated to motor controller a viper sub 10. any suggestions I am including a picture of the setup. could the proximity to the motors and the wiring wrapped on one side of controller allowed the controller to overheat? could just moving the wires away give enough breathing room for the controller or do I have to move it closer to the reciever and further away from the heat of the motors? or could the motors overheated and caused problems??

I bought everything but the servos from caswell so there are no wild card parts in the wtc setup they are all known factors

[He Who Shall Not Be Named]

Good job on chronicling the situation and the problem, Robert.

Your installation, though a bit ratty looking, is no worse than the suitcase stuffing I've been accused of! That's not the problem.

The problem, is the solution here: Your ESC's thermal shut-down feature is kicking in -- you're motors are drawing more current than the ESC is designed to handle. That's an older style 3.5 two-motor, two-shaft motor bulkhead. I assume that you are using the provided 3:1 gear reduction units on the wet-side of the motor bulkhead? If not, install them to unload the motors.

If you are using the gear reduction units, then you either have to upgrade to an ESC of higher constant current capacity or learn to keep your lead foot off that throttle stick.

David,

[robert lipsett]

yes I am using the 3:1 reduction. my lead foot is necessary because of the weight. at full speed I can keep up with it. can you recommend a good controller that will have a bec and also be able to keep up with the current draw of the motors and also fit easily in the position of your wtc. as a second idea are there any motors that would suit my requirements. I would appreciate the two options?

[He Who Shall Not Be Named]

yes I am using the 3:1 reduction. my lead foot is necessary because of the weight. at full speed I can keep up with it. can you recommend a good controller that will have a bec and also be able to keep up with the current draw of the motors and also fit easily in the position of your wtc. as a second idea are there any motors that would suit my requirements. I would appreciate the two options?

How would you like to be my Gina-Pig?

MTronik's is sending Caswell-Merriman an evaluation ESC of high motor current capacity and with a BEC rated for 5-Amper's continuous. If you are prepared to put it into your SubDriver, and run the **** out of your Type-7 with it installed, then we kill two birds with one stone: The new ESC gets a good field-test, and you solve your ESC-BEC needs.

But this has to happen as soon as I send you the unit.

Game?

David,

[vital.spark]

Robert,

I have the Revell Type VII which is a baby next to yours and would love to see pictures of your Type VII. When you recharge your Lipro's, one should never leave them unattended due to the fire risk. Down here in New Zealand last year, a house burned down wlile leaving a R/C Helo charger on over night!

Myron

[robert lipsett]

I garauntee that the unit will be in and tested within a week of arrival. send me a private email and I will paypal you the money for the unit or bill it too me through caswell. and to answer the question of charging the battery unattended, I did not I had it on discharge not charge which is safe to leave alone unlike charge. I think I will run it on the surface at max speed to do the initial test so it will be visible and be able to be rescued easily in case something goes wrong. here is a picture of its current configuration. as of the moment it needs more external detailing. its my first sub and I am trying to get it reliably operational. its been going together for 20 years and it has sunk many times before it has become reasonably trust worthy the first picture is how it is now and the later pictures are what it used to be with wooden decks and planes instead of plastic decks and planes. the kit was not that great a kit as I look at most of the subs now but I refuse to let it get the better of me. this is a learner sub. the next will be better. and yes the kit was supposed to be assembled with wood for decking and watertight compartments

[He Who Shall Not Be Named]

No need to pay, we're getting this as an evaluation sample from the good people at MTronik's.

Do you have or can you get hold of an Ampere meter? If so, put it between the battery and the SD as you stick the propellers into the water and hit high-throttle -- I want to know how much current the fully tasked system will pull. We'll get into the details of the testing when we get that ESC into your hands.

No need to apologize about that submarine -- hey! ... it works. That's what matters.

David,

[robert lipsett]

I have no amp meter. do you recommend one that I can buy cheap and get fast. I was looking on ebay for one and saw some 3 1/2 inch ones for 8 dollars plus shipping but they need over a week to deliver

update
just checked I do have a multimeter that has a 10a fused ammeter port. if this device requires more then 10 amps my fuse will blow. do you want me to connect it between the battery and the wtc. if that is the case I will not be able to sail the boat but will have to have it tethered in the water unmoving and unable to unload the props by moving the boat. I just want to know how you want me to make theses measurements so that they conform too your needs. do I need a more powerful amp meter?

stupid me I just read between battery and wtc for total amps drawn for bec and motors.

[He Who Shall Not Be Named]

Don't worry about measuring it. I'll give the ESC the acid-test here, then will turn it over to you. Just run the heck out of it and report back with its performance.

David,

[robert lipsett]

update. recieved controller today and installed and calibrated it. So far its a simple to connect and calibrate as the viper 10. I have been having some moisture problems in my wtc but all the times I pressure tested it in the pool I had no leaks, today since I was going to be testing out the new esc I powered it up for a pressure test this time. I noticed at slow engine speed that I was getting some small bubbles from around the shaft area of the port motor. this is the same side that leaked and I replaced last year when my wtc was new. I unbolted the motor and when I pulled it out the oilite bearing from the seal was on the shaft and not in the seal. Could I have possibly have put the motor slightly crooked and over time the off center shaft spun the bearing out of the seal and made a leak. Anyways I polished up the shaft back to its original luster and have installed a new seal from my spares. I am currently waiting for the rtv to dry before I retest for water integrity. The other leak I had was from a pushrod that only leaked when it moved. The pushrod was slightly tarnished near the seal and polishing it up had no effect on the leak. A closer inspection of the rod revealed that it was not exactly true in the area of the seal. I am wondering if these slight eccentricities caused the push rod seal to wear slightly over time. the push rod controls my rear dive planes so you know it is always in motion. Just waiting for the clear sealant to dry right now so that I can resolder and neaten up my connections for the wtc and give it a good pressure test before trying to run an extended cruise.

[He Who Shall Not Be Named]

You've addressed the dropped Oilite bearing problem correctly (happens from time to time). You can fix that pushrod problem by pulling the pushrod out, coating the seal area of the rod with a layer of thin formula CA (to fatten it up) and that should make the pushrod seal leak go away.

Need any parts?

Give that ESC hell and see if it can keep the magic smoke inside. Nice thing about these new ones is that they have double the current carrying ability and feature a BEC that can supply up to 5 Ampere's continuous -- neat!

Thanks for the reports. Keep 'em coming.

David,

[robert lipsett]

I just replaced the pushrod seal with another one that I had and I am also replacing the pushrod with a straighter and cleaner piece of brass pushrod. Every time I touch this thing I am learning something new

[jlday1256]

Robert:

Actually, that is a really nice looking boat. I notice the emblem on the sail, did you get some inspiration from "Das Boot"?

[robert lipsett]

yes I was inspired from das boot which is actually when I started it. Sea trials today. The first mission lasted 15 minutes. I ran it for 10 minutes on the surface and when I tried to dive it wouldn't flood. for some reason the battery didn't last very long on a 5000 mah cell and the failsafe was kicking in and I thought I had screwed it up and it wasn't working. Aquick replacement of the battery and visually inspect the sub driver and all appeared good and dry. Away on another mission, The boat only really moves good at almost full throttle due to its weight which really kills my battery life. So I am sitting back relaxing and trying to get a feel on how to dive my boat using forward and aft planes in a coordinated way. I am 15 minutes into the mission when I loose sight of the boat and probable ideas of where the boat could be. All stop and wait for the positive bouyancy to take effect. I blow the tanks and the sub pops up about 120 feet away from me in the middle of the pond. She seems dead in the water and I am unable to tell if she is receiving me. or if the motors have gone dead. I wait a few minutes and get no response so its time to go for a swim. I swim all the way out there and push the boat back to shore. I do not touch the boat excessively during towing it back to shore so that when I get back to my transmitter I will be able to see if the boat responds to control signals or if the motors are giving me problems. I pick up the transmitter and the controls respond and the engines respond full power. So what gives? I decide that if the control has overheated or the motors they can't have cooled off enough too much so I hit full power and take her for a cruise. the cruise lasts for 15 more minutes. I stopped the cruise because the boat was getting slower and it started to turn on its own. Upon further investigation it was discovered one of the props was dragging weeds. I also noticed the boat was sagging in the rear a little. This is not good. I had a slight flooding casualty in the engine compartment of the sub driver. Damn I thought I had cured that problem. I had a quarter inch of water in the sd and lost the snort pump functioning probably due to water, lets hope when it dries out it decides to work. The question is did my motors stop becouse of an overheat and then the flooding cooled off the controller since it is in the lowest portion of the sd or did I have a bad connection with the battery and the motion of pushing it back to shore knock it back into conducting power again? battery updates the short running battery took 2000 mah and reported I cell overcharge. the other battery took 3500 and also reported 1 cell overcharge. the short running battery need to go into recover mode to start chargin due to too much power being drained from it, it was under voltage.

[He Who Shall Not Be Named]

A detailed report. That new ESC is rated for 20A continuous -- Those motors stall at a bit over 10A a piece. One maybe was close to stalling dragging weeds, and you had to high-throttle them anyway. Maybe the ESC went into thermal shut-down mode. The MTroniks ESC's do that, and re-set once the temperature drops below the cut-off threshold. Maybe that's what necessitated the swim?

David,

[robert lipsett]

I wish I knew if the boat had any power or not when it was out there. I couldn't tell if anything was responding though If it was in thermal the 15 minutes more after a 5 minute rest should have done it again. it looks like a mystery on this one. I am going to try to find the new leak and go again. maybe mon or tuesday before I can try again

[He Who Shall Not Be Named]

Sounds good. Next time, run the boat hard, but close in to shore as you walk alongside it at the waters edge. If it goes dead in the water and the rudder and other control surfaces can still be wiggled, then you can assume its the thermal trip.

Good work, Robert. You're keeping up your end of the deal.

Give me the gory details on the source of leak ... and don't be shy about asking for parts.

David,

[robert lipsett]

Well I discovered the source of the flooding and it was the starboard motor seal. The starboard seal was leaking three times as much as the port seal and pushrod seal leak combined. After taking it apart there was some surface rust on the shaft that wiped off with a towel and there was no evident pitting. I polished the shaft up and it was smooth and shiny and replaced the seal. A quick pressure test this morning and no bubbles. Well off to the pond I went today and I was running it hard for about 15 to 20 minutes and the boat came to a halt. about 30 seconds later it surged for a few seconds and ground to a halt. I then walked out to the boat and my snort system was functional and my servos were moving there rudder and dive planes. So now I know the boat isn't losing battery power, I made sure of that by buffing up all the posts screws and connectors. I could feel heat coming from the motors and the controller. The metal mounting platform was hot from possible the two motors and the controller. I am wondering if the motor heat is being conducted to the controller and making the controller over heating worse. The motors have 7v stamped on them but I have been running an 11.1 lipo battery. I have reduced the pitch of the props originally per meriman's suggestion because earlier attempts with a smaller mah battery caused so much heat in the battery compartment that the cap was blown off and caused flooding which sank the boat. The boat moves at a slow walking pace at almost full power so I have to really push the engines to get that speed out of them. the smaller batter was a 3300 mah battery and the larger one is a 5000 mah battery. the larger battery was not too warm. in fact I have had airplane batteries heated up more then this battery was. the 3300 mah batteries were for airplanes and after two trips for the sub they were useless for flying. not strong to keep the plane in the air let alone boost the plane past 80 mph. I only include this information to give a better picture of my problem that I am facing.

[robert lipsett]

I finally had time too make my modifications to the subdriver unit. the esc is now mounted at the opposite side of the subdriver away from the motors. A minor dumb mistake occur while working on the wtc, I mounted the servo arm one tooth set off on the rear dive plane, I noticed this but since most of the running was going to be on th esurface and I was really trying to do a motor test I figured that adjusting the forward planes higher for a rise would compensate for the error. And now on with the show. Full throttle to move the lead sled to a walking speed. All seems good for the first 7 minutes, do you know how boring running a submarine is on the surface ,when someone walks up behind you and asks if your submarine will dive. Tanks vent a little down on the forward planes and under she goes yaaaaaa. Hey that felt good and I brought it back to the surface fairly quickly, lets do it again. A little more down forward planes. Wow that thing went under quickly. I lost sight of it!! All Stop and wait for it bouyancy to surface the boat. 30 seconds later where is it, oh noooo!!!. Emergency blow! 3 second burst. Pop sitting on the surface like nothing happened, I guess dave does know what he is talking about when he designs a subdriver. The badly adjusted rear plane made me dive very fast and I think I got hung up a little under water or I was a lot deeper then I thought. Full throttle on the surface again and at the 15 minute mark the engines cut out again. I have full radio control but no motors. 15 second wait and I have a few second burst of power. I have had multiple burst of power after a short wait period unlike when the controller was mounted directly under the motors. I need some ideas on how to cool this controller before I go to my plan z mode of removing the controller from the wtc and using it in the free flood area of the sub to have it liquid cooled. Where I will fabricate a mounting that can be quickly connected or will be out of the way of the dog bones I do not know. I might have to knock out one of the unused pushrod seals to pass the j connector into the wtc to power the radio and also to run motor wires through. I am looking for some more reasonable ideas before I go to a drastic procedure

[He Who Shall Not Be Named]

Replace that 11.1v battery with a 7.4v unit and the motor heating will go away -- the over-heating extends to the ESC and it shuts down on you.

David

[robert lipsett]

Well the 7.2 volt battery finally arrived and I have had a window of opportunity to test the sub again and its controller. My rear dive plane pushrod is sticking and is jammed in a neutral position which shouldn't be too much of a problem since I will be testing the controller running on the surface. Both props do not start spinning at the same time so I am going to have to investigate if one is binding a little more then the other one. I ran full out on the water for 30 minutes until the battery went dead, a 5000 mah battery. I tried to dive the entire time using only my front planes but was unable to force it under water after I flooded my ballast tank, I might have to try getting some new props with the regular pitch in them. The props I have on right now have a reduced pitch because the battery overheated once with the higher voltage battery and blew the cap off the battery compartment. With the reduced voltage I might be able to run the normal prop blades without heating the battery up since this one felt room temperature after the run. The thing that worries me was the battery ran dead in 30 minutes but there was some extenuating conditions. one was that I had a servo in a stalled condition and the other was that I stupidly left the snort system operating pumping throughout the 30 minute run. Its starting to get a little too chilly to fetch the submarine now, hopefully I will have one more run in the pond before it gets too late in the season.