|Mar 25, 2005, 09:56 PM|
1/12 scale Patrol Boat River (PBR)
I normally built and run sailboats, last summer I managed to get one of the few prop driven boats I own hung up on some rock that chewed up the prop and rudder. Since then I have given jet drives some serious thought. I know I can still get it hung up, but with no prop it should come off with just a few scratchs to the hull. About two months ago I came across some plans on Ebay for a 1/12 scale USN Patrol Boat River (PBR) or Pibber, that I had to have plus the price was very reasonable. I had considered several other boats, luxury yachts, ferries, etc, but the PBR seemed to be the right boat for what I had in mind.
So now that I have the plans I need running gear. All of my sailboats are basic 2-channel setups, same for prop boats I have, so this is new territory for me! After several internet searches I came across Keher Modelbau (www.jet-drive.de). They offer several jet drive sizes as well as motors and all the parts you could possibly need for a project like this. They also a 1/12 scale Pibber kit, but I have decided to scratch build this boat (if things donít work out, Iíll order the kit). The plans recommended Graupner drives, but Iím not real fond of how they look. The KMB drives look a little more realistic to me, and were about the same price as the Graupners listed at Hobby Lobby. I have on order 2- 28mm drives with Johnson 700 motors with water cooling and one of their 70A forward only speed controllers (also water cooled), as well as the servo linkages needed for steering and reverse. Since this is new ground for me, I have decided to wait until I have the running gear before starting construction on the hull. Mainly to see if I need to adjust bulkhead locations or deck height to fit these drives and motors.
Once I started planning thing out, it seemed that this boat was going to be jam packed hull of hardware. I have several ambitious ideas for this boat. Since the motors and ECS are water cooled, I plan to run the output water to the bow gun tub and out the twin 50 cals so I can hose down the kids at the pond. The water will be provided via a small pump with a pick up and screen mounted towards teh stern and near the keel. Between the motors and guns would be a small 3-way solenoid valve that would dump the water overboard like a builge pump drain or send it to the gun tub. The tub will obviously have to be servo driven for elevation and rotation, because kids like to run around . I think I can wire a machine gun sound board in series with the solenoid valve to really freak out the kids. Then there are the running lights and engine sound boards to consider, which means I have to look into MCDs channel expander or similar setup.
Iím currently working on a wiring diagram that I will post as soon as I'm finished. I would like your input as to whether I should run 2 Ė 6V gel cells (for longer run time) or run one 12V for the motors and accessories, and one 6V cell to power the RX (as far as I know there is no BEC on the ECS).
Thanks in advance, will post more pics. when I have them.
|Mar 26, 2005, 06:50 AM|
Hi, Big Sails!
Recently, I got my hands on a 1/12 scale PBR made by a guy in Michigan who no longer produces kits. I went ahead and ordered the Graupner units and have a set of Speed 500's with water cooling to power them. If only I would known about Kehrer Modellbau! Thanks for posting your info! At least, I can detail my kit with some military hardware as 1/12 scale is next to impossible to find! Also, getting 1/12 military figures just don't exist to my knowledge.
The Tamiya kit is great for details.
As far as your question on gel cels, I'm planning to use 10 cells and fast charge them.(I'm a airplane freak, also). Good luck and look forawrd to your layout pictures!
|Mar 26, 2005, 03:20 PM|
I'm working on a wiring diagram for this PBR, and think I've come up with a pretty good layout, but several questions keep popping into my head.
1) Are most dual motors wired to a single ECS in parallel or series? (second photo) Or do most people run a seperate ECS for each motor?
2) Since this is a forward only ECS, has anyone tried to wire in a servo to operate the reverse gear and still run the motor forwards?
3) After looking at all of the components I might possibly put on this boat, I think that running two 6 volt gel cells in series will give me the most flexability in wiring all of the components. I can tap into one of the cells and run all of the 6V gear and still have enough power to run the motors and pump. The alternative would be to run a 12V cell and a small 6V cell, but I would prefer to run the same batteries if possible.
|Mar 26, 2005, 11:20 PM|
When I use a single ESC for 2 motors, I usually wire the motors in parallel - because I usually have counter rotating props. I have 6 models with two motors. Four of the models have the motors wired in parallel. The other two models have separate ESC's for each motor.
Since you have a forwrd only ESC, the reverse gear servo would be plugged into the receiver and requires another channel or two. Why two channels? One reverse gear servo for each drive unit, that way you can go full ahead on one motor and full astern on the second motor - spins the boat in its own length. I'm not sure if the PBR's were set up that way though.
Based on your main diagram, the following is my suggested receiver plug ins:
Channel 1 - Steering, right stick moves left/right
Channel 2 - Water cannon elevation, right stick moves up/down
Channel 3 - ESC, left stick up/down
Channel 4 - Water cannon rotate, left stick moves left/right
Channel 5 - Reverse gear, should be a switch on top right corner of Tx
Channel 6 - Channel expander
|Mar 27, 2005, 08:30 AM|
Frank, it's funny you mention the Tamiya kit. One of our boat club members uses smaller scale models as a guide to scratch build components when detailed plans are not available. Currently he is detailing a WW2 German Schnelboot (German PT boat). I have the Tamiya kit and will use it in a similar manner. There are a couple of areas on the plans I purchased that need to be detailed and the Tamiya kit will provide some insight.
CG, Thanks for the input on the motors and ECS. I had planned to wire the motors in parallel, I just realised that if I had wired them in series I would have had to run 24V batts to keep 12V across the motors (Kirchhoff and Ohm at work again). I have not purchased the Radio gear yet, but I ahve been looking at the Futaba Skysport 6, which can be expanded using Model Control Device's (MCD's) 8-channel expansion pack. Since I am right handed, I had planned to set up the throttle and steering on the right side stick and the "Water cannon" controls on the left side stick, with the reverse A/B position on the gear toggle. From the research I've done, I can not tell if the reverse plates on the original PBRs were controlled independantly or linked together. It would be nice to have independant control, but to keep thing simple I will use one servo for reverse and link teh two plates. The third photo in my original post shows the motor arrangment KMB suggests. The upper servo between the motors appears to be the reversing servo linking the two reverse plates.
|Mar 27, 2005, 12:00 PM|
Channel 1 - rudder, right stick left/right
Channel 2 - dive planes, right stick up/down
Channel 3 - Throttle, left stick up/down
Channel 4 - Ballast tank, right stick, left to take on ballast, right to blow ballast
|Mar 27, 2005, 01:06 PM|
This will be the first boat I've built to use a two stick TX, with the exception of my Robbe Atlantis which uses a Robbe F-14 Navy radio (everything else has been pistol grips). I had considered pulling the radio gear from the Atlantis, because getting a new one would pretty difficult, Iíd rather not strip the Atlantis if I didnít have too. Since I don't need the radio gear for some time, I may place my order for a standard F-14 (non-Navy model) and wait like everybody else (I talked to the guys at Harbor Models, they are expecting new radios at the end of April or early May). I do like the fact that the Robbe radios can expand channels just by plugging the expansion modules directly to the boards, I only chose the Futaba because it was readily available and could be expanded using MCD's products and a little TX modification.
As for control layout, I thought it might be easier to set up the throttle and steering on one stick and the gun control on the other (at least easier on me). If I set leave the throttle on the left and set up the steering on the left stick, I can use the right for the gun control. It is just speculation at this point, I may change to a more conventional setup once I get the boat on the water.
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