Arkmodel Red Shark

[Sonnich]

A local ebay seller had a few kits for sale, so I decided to try one.

Trying to buy one from Ark Model seems over complicated. The discriptions are a nightmare to read through, and you just dont know what you are ordering......

The ebay seller also had 2 verisons,.....so I just bought the most expensive one, and hoped for the best, as the price difference was marginal
It cost about the same as the Robbe seawolf when it was around . 200 euro


It seems I bought an ARTR version.
I thought it would be a complete kit, that I would have to assemble myself........but it is allready assembled.

At first it looks great, but looking closer at it, it is a very poorly built cheap model :-)
The paint chips right off of all the shiny plastic, as it has not been prepared at all before it got a spray coat.
The prop is just a plastic impeller, that seems very fradgile. The motor does not seem to turn freely.
The rudder and dive planes are very wobbly with lots of play. I dont like it.

But, it was inexpensive, and very simpe as this is a dynamic diver.
So I will try tweak it a little, to make it work out.

Overall, I like it...and I sort of got what I expected

[Sonnich]

Few more pics...

[Sonnich]

Ok...got it in the pond today. Yesterday, I got everything installed, and trimmed out at home.
One of the 6V lead batteries was dead, so I decided to use 2 3S 5000 lipos. in parallel, to get 10 amps.
Still installed one of the lead batteries as ballast to weight the sub down.
Having only a shower, I used the box, and some plastic to make a test wet dock for it :-)
Got is trimmed out fairly well eventually.

Today, I took it to the pond, and it performed great. Really fun to drive arond. It is very respnsive.
Really like the way it handles.

Unfortunatly, the motor burned up.....it started slowing down, so I brought it back......when I opened up the WTC, white smoke poured out of my sub.....and that nasty burnt electronic smell filled th air :-) Crap.....

What I yhink hppened is that the prop/propshaft got pushed forward, and there became too much friction, and the motor burned.

I had not idea that the motor is only held in place by o-rings in the motor tube.......so you can acctuallypush hard on te prop, and the motor will move forward....and then the prop will but up against the bushing in the tail.....and create lots of friction.....enough to burn my motor :-(

Opend up my motor, and it is totally black inside. funny thing is that the brushes look like new.....in the picture, I sanded the comutator.....it was dark. But I think a winging let go, and it shorted out......there is a loose strand.

On the website is says its a 12V 8500 rpm motor, and 540 size. Anyone know what I could use ?

Brushed motors are not that easy to find any more.

[Sonnich]

more pics.......

[Guest]

12v 8500RPM. Sounds an odd wind. Most of the common 500 size motors for 12v tend to be either around 6k RPM or 12K RPM.

[Sonnich]

Numbers are just taken from the Arkmodel site.....who knows what it is :-) Do you have any links to a suitable moor in the uk ?

[Guest]

There's this motor from Engel. They use this motor in their Lafayette and 212 kits, and it pushes them along at a fair old clip. Not sure on the pitch and diameter of your prop, but it should be okay. Or you might consider going brushless?

http://engel-modellbau.eu/shop/en/Electric-Motors/E-Motors-Brushed/Electric-Motor-Speedster-540-12.html

[Sonnich]

That is a nice one...a shame it is not in stock :-)

[Guest]

Another, this time a UK supplier-

http://www.componentshop.co.uk/mabuchi-555-dc-motor.html

[Sonnich]

Awesome thanks. Ordered it :-)

[Sonnich]

Well, I also contacted the ebay seller in germany, and asked if he had a spare motor.

No motors in stock, but he would sell me a complete new submarine without radio for 70 euros including shipping.......so that is really great service.

So it looks like I will have another Red shark sub.......that I can modify


Here is te seller if anyone whants one.

One with radio, and the other without.

http://www.ebay.de/itm/RC-U-Boot-Red-Shark-402-Masstab-1-72-Submarine-inkl-elektr-Fahrtenregler-/182613685008?hash=item2a849fb310:g:k7MAAOSwpONZOoW9

http://www.ebay.de/itm/Red-Shark-U-Boot-Komplett-Bausatz-/172718639146?hash=item2836d5482a:g:GKUAAOSw8HBZOAsN

[steveuk]

I was very interested to read your experience with the Red Shark. A friend bought one of these too. He has experienced exactly the same problem - his motor gets extremely hot and slows down. We are trying to figure out what is causing the friction. Personally I suspect the shaft seal is getting hot. Perhaps water is not enough to lubricate it. But you have a different theory. Did you find your motor has physically pushed forward in its mounting. Did you have to push the motor back to its original location??

[Sonnich]

When I got it, I had no idea of how the motor was installed. I thought it was screwed into a motor mount, and then glued into place. But it is just a snug fit in the "motor tube", only held in by O-rings , and you can push it backwards about 1cm, or pull it warwards, until the prop hits/rubs on the brass bushing in the tail.

I can only imagine that the thrust created by the prop can move the whoe motor and shaft forwards, and creat problems.

When I get my new motor, I will see how I can retain the motor, so it can not slæide forward.....shoud be a pretty easy fix. The motor shaft to prop shaft adaptor is so badly aligned too, maybe will have to replace it, as it does not run true at all......and that is not good either.

Im also going to install a heading lock gyro to control pitch of the sub, as it was a bit of a handfull to keep it steady under water.......but hey, I only got 5 minutes of practice last time I was out :-)

[steveuk]

The prop shaft adapter misalignment sound like a definite cause for extra load on the motor. Propeller against brass bushing - I can't imagine that causing too much friction. Maybe a thrust washer here would quickly rule that out. I will watch with interest to see how your solutions progress.

[Sonnich]

My prop was glued on with some gooey stuff, and that + some of the plastic had melted, causing friction......a real mess.