|Nov 21, 2011, 12:39 PM|
I recently bought a small plastic police boat online for my 4 year old grandson.
As I expected, the motors didn't last long. (each motor pod has a separate speed control for steering and acceleration.
What I would like to do is remove both pods and replace them with good quality small motors with their own drive shafts (exiting where the pods were).
Also want to install a rudder and servo.
I already have several orange 2.4 receivers lying around that I can use, and a spare transmitter, (going to throw out the 27 mhz radio that came with it.)
Don't quite know where to start. I know a little bit about it, but not enough to make these selections below. Been modeling for 50 years, but a lot of this new technology is NEW to me. (been away from it for while)
Questions I have:
Motor size/description? (water cooled or not? Should be reversable.
It's not a speedboat and he's only 4 years old, going on 5, (or is that 12), so he won't need mega power, but it should move along when required.
Should I go the twin motor route or just put in a single motor for simplicity?
Should I use a hard shaft or a flex shaft?
ESC? (depends on motor and batteries selection I guess, right?)
(BTW, what is a a UBEC?)
Prop/s- size and pitch?
Batteries? (I'm thinking Lipo or NImH)
My grandson loves this boat, and I would like to get it back in operation for him by spring. I have a limited budget, and the boat wasn't an expensive one to begin with, but it performed well while it ran, has a good hull shape (all plastic), looks nice, and is worth saving if I can do it for a reasonable cost.
I'm pretty sure that HK has everything I need to do this, and their prices are good, just not confident I can pick out what I need from their extensive lists.
Can anyone offer me some advice here?
|Nov 21, 2011, 01:55 PM|
What toy did you buy? That would help steer you in the right direction for motors, etc. Pics are always helpfull, too. Motors for slow-ish scale type boats are cheap when purchased from surplus stores, or even scavanged from other toys, broken vacuum cleaners, etc. If you already have battery packs for other hobby stuff, keeping with the same type/size will help you. Shafts, tubes, etc can also be simple brass stock from your local hobby shop. Flex drives are more suited for high speed stuff, I would say solid shafts would be easier. Depending on the boat, you can decide on one or two motors. One is easier, but sometimes two makes more sense.
And a UBEC is a Universal Battery Eliminator Circuit. This electronic device takes the drive pack voltage and cuts it down for the receiver so you don't need to carry the extra battery pack. Handy if your drive pack is more than 8 volts. Might not be needed if your receiver is labeled as BEC itself. Those can usually take up to 8.4 volts. Common on rc cars.
|Nov 21, 2011, 07:50 PM|
I'll attach some pictures here of the boat.
It's sort of all apart at the moment, didn't see any point in putting all those screws back in yet.
One motor pod is apart too. They were glued together, so I pretty much had to break it to get it apart.
The problem with this propulsion system is that once one motor begins to fail, you can only go around in circles, which is what happened.
I think it would be easier to keep the water out of the bottom of the hull with only one motor shaft than it would be to reseal those motor pods.
I'm thinking of replacing all the guts with a traditional RC rebuild inside, servos, esc, etc., and putting a regular rudder on it.
On that note, if I were to use the two shafts that the original motor pods used, and put twin rudders down through them, would a centrally located single prop work.
In other words, would it turn OK?
As for the battery packs, what I use in my RC sailboats is NIMH 4.8 packs, with the Turnigy individual LSD 1.2 batteries, in a 4 cell battery box.
Powers servos and receiver, no motor.
I can sail all day with one set of batteries. The wind is free...
His attention span is not that long.
Is there some combination of motor, esc, and NIMH that will work for him?
I do have some 8 cell battery boxes too which would be (9.6 volt.)
The advantage to these cells is they are cheap, very reliable and can be charged safely indoors. Also would provide ballast, so I could chuck the concrete.
There is plenty of room in there. The downside here is that comes to a total of 12 individual batteries to charge (4 for the Dx5e TX)
I could also go for a 2S Lipo omboard setup. I think that comes to 6.8 volts, correct me if I'm wrong here.
Charging in the garage again., but they aren't too expensive and they are light and small.
There is a 6 volt, 5 cell nicad pack (soldered cells), that came with the boat, and a plug inside the removable hatch under the lifeboat. This pack powers everything, motors, radio etc.
I'm thinking a charge plug could be incorporated there, so I could just leave the cells inside the boat, whichever kind I use.
Don't want to be removing all those screws every time it needs a charge.
Sorry for the "War and Peace" post here, but I wanted to be as clear as possible on what I'm trying to do here, so you can help me.
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|Nov 21, 2011, 10:29 PM|
Joined Sep 2006
I would ditch the pods and run twin shafts and locate the prop in the concave part of the hull where the pod was with a rudder behind each one. you could make something work with a single prop but I think it will be easier to make it a twin drive
|Nov 22, 2011, 02:58 AM|
I would agree with hazegry on the twin motors, props and rudders, just because of the big cavities in the hull. As for batteries, anything from a 6 or 7 nimh cell rc car pack to a 6 volt gel cell can be used with a car type speed control. Traxxas makes a few that would work well and can be found on e-bay for small bucks. Both motors can be run from one control. With the right motors you may even be able to re-use the props. Something like a mild speed 400. You can even use silicone tubing for motor to shaft couplers.
If you want to keep the boat closed up for charging stay away from lead acid type (gel cells, etc) batteries.
I can't think of any reason to keep the concrete.
Sounds like a fun project that you should be able to pull off without spending a ton of money.
|Nov 22, 2011, 03:54 AM|
I agree with all others, but not for the rudders: as you know as a sailorman, they act as brakes and this boat is originally rudderless.
The differential speed of the motors is much more efficient for steering than rudders and you can turn in place at no speed.
I also prefer brushless motors, more robust than brushed ones. For the car ESC, you must choose one having a "Crawler mode", allowing to reverse immediately the motor, which is required to use for a motor steering boat. I prefer the HobbyWing ones, they are cheapest, easiest to program even without program card (but a program card is a must), have the "Crawler mode" and I well know them!
You can use a hard shaft with a diameter corresponding to the original props. The silicon tube for coupling is a good solution, you can also use an articulated coupling, but this is more expensive.
|Nov 22, 2011, 10:33 AM|
I would agree with boater dave in all except loosing the concrete, that is there for a purpose ie ballast. Going with conventional shafts and speed 400 motors and a single ESC would be the easyest way to go and the cheapest also. You don't need a high priced system in a childs toy. It will last allot longer than the original system without breaking the bank.
|Nov 22, 2011, 03:40 PM|
Joined May 2004
I have a similar boat, the pods rusted solid after a few months, as the moisture had no way to get out...
I'm in the process of converting it to a single motor for weight reasons; the hull won't carry two 400 size motors, hardware and RC gear without sinking in way too deep.
I also had ballast in the hull, which I removed to get more boyancy.
The battery will be as low as possible in the hull to keep the CoG low, but the boat is still a bit tender.
I closed the cavities where the pods sat with ABS sheeting to get more boyancy.
A single stuffing tube will exit through the bottom, with a small rudder behind it.
|Nov 25, 2011, 01:12 AM|
Are they that heavy, that removing the ballast won't even it out?
I was planning on plunking an 8 cell NIMH battery pack in that ballast space and putting one motor on each side of it with a rudder behind each prop.
As a basis of comparison, what size are the original motors?
Would it be possible to use the original electronics, and have the two motors operate the way they did originally, to steer the boat? (only better quality of course and inside where they stay dry.)
I don't want to alter my DX5e sticks (although I guess I could) to use it as a double throttle setup. (Spring to center on both sticks).
Admittedly the 2.4 radio would be less hassle at the pond.
Any thoughts on this?
|Nov 25, 2011, 06:40 AM|
Joined Feb 2006
What size are the original motors? A like for like change might be the simplest solution, but mount them inside the hull and connect them to the props using shafts. Seal any unwanted holes - Styrene sheet + filler, create new ones for the stuffing tubes. Use the existing electronics - this might need re-siting to accommodate the new placing of the motors.
|Nov 25, 2011, 08:22 AM|
I'm amazed at all the help I'm getting here for a mod to a child's simple toy boat.
Thank you all very much.
I'm one of those people who have been in model building and RC for many decades but never really grasped electrical theory, and don't know much about modern RC boats electrical stuff. (motors, current, amps, fuses, escs, becs, batteries, whew!!)
I can build just about anything, but this part I need a lot of help with, so again, I thank you all for your input.
When I get into it, I'll post some pictures as I go along, so maybe it will help others contemplating the same mods.
BTW, I haven't seen anyone mention cooling, is that going to be an issue with these small motors?
|Nov 25, 2011, 08:27 AM|
At my local electronics warehouse (Sayal Electronics) they have some small surplus type electric motors that look like the ones on the boat, but again, I don't really know what I'm looking at as far as voltage, amps, current etc., so I don't know if they will work or not.
Certainly the price is right!!
I could take one of my boat motors along with me to make a comparison as fart as shaft size and physical motor size goes, but not sure if I can match them electronically.
|Nov 25, 2011, 09:27 AM|
|Nov 25, 2011, 10:38 AM|
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