Conversion Issues

Discussion in 'North Atlantic Treaty Combat Fleet' started by Bob Pottle, Jul 9, 2008.

  1. Bob Pottle

    Bob Pottle Well-Known Member

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    Tom Cromwell and I spent over 3 hours tonight working on models and measuring pump outputs for conversion from IRCWCC to Treaty specs.

    Nagato is equipped with a BC large pump. The pump passed with an output less than the maximum allowed 1.25 gallons (US, not Imperial gallons) per minute. We looked at a set of smaller 28 mm props that should reduce Nagato's speed to less than 33 sec/100'. When last run (2006) Nagato was a lttle faster than it's IRCWCC speed of 24 sec/100'.

    I've always considered Carl Camurati's pumps to be the best available, and the small pump from Black Prince was no exception. With a Mabuchi 380 RS it's output was over 1.5 gallons per minute - about 0.4 gallons/min more than Nagato's large BC pump, and over twice what the Black Prince is allowed (0.75 gallons/min).

    We switched to a '0.5 unit' pump outlet removed from HMS Gorgon. That severely decreased output (by 2/3 - only 0.5 gallons/min) and caused the motor to overheat. Other outlets will be made and tried until the output is close to the allowed 0.75 gallons/min. If necessary a less powerful motor will be fitted.

    Monitor HMS Gorgon uses the same 0.5 unit outlet, but has a less powerful generic 380 motor and an old Goff pump housing. Its pump wasn't tested because it can't possibly pump as much as Black Prince's pump using the same small outlet. It has less than 2/3 of allowed pump capacity.

    CLAA HMCS Prince Robert has a Camurati pump but another generic 380 motor and the same small outlet - definitely less than 2/3 of allowed output. Gorgon has never been sunk, being very small and hard to hit, so there's no plan to install a more powerful pump this year. Same for the slightly larger Prince Robert.

    The last pump considered tonight was in the armoured cruiser Minotaur. It has the same Mabuchi 380 RS motor as Black Prince but on a Goff pump. There was no need to test because it would have a very similar output. Like the pump for Black Prince it will need an smaller outlet restrictor to decrease capacity.

    Armoured cruiser speeds may be hard to adjust to slower Treaty speeds. Black Prince already has large drag discs ahead of its props and when last battled was running close to 26 sec/100'. It will much less powerful motors. Minotaur was running at 26 sec/100' without drag discs but with less powerful motors than BP. A happy medium needs to be found.

    The plan is for Tom and me to work on pump outputs and modify drive trains over the next 3 weeks, then run speed trials in the first week of August.

    Tom took possession of my partly built WWI 15" gun monitor HMS Erebus and will build it to Treaty specs this summer. We worked on some of the internal gear and planned the general layout. That will give the fleet 3 Royal Navy monitors: Class 1 Gorgon, sister Glatton and Class 2 Erebus.

    Steve Hill will drop off HMCS Ontario for conversion to Treaty specs after my vacation. We expect 6-8 ships to be ready for the first battle on the 2nd weekend of August.

    Bob
     
  2. crzyhawk

    crzyhawk Well-Known Member

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    Hey Bob that sounds great! I'm trying to figure out how to use an ESC to control my pump flow but haven't gotten it figured out yet. I think I might try using a pot on the Courageous as well this year as the restrictor I used on my Invincible was holding it down below my minimum amounts and I sank more then I really should have.
     
  3. GregMcFadden

    GregMcFadden Facilitator RCWC Staff

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    Mike, simply put the esc on a toggle channel on your transmitter. then set the end point (I assume you have this capability) to something less than full travel to reduce the speed of the pump.

    The other option, depending on the esc you have, is to set it (if this feature is available, probably not in the boat specific esc's) to helicopter mode and it will try to keep the motor speed constant no matter the load.
     
  4. HMCS

    HMCS Active Member

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    Good update Bob.

    I have to test my pump as well, though it's a BC micro pump, very tiny, I'm sure it will be under the .75 gpm limit. I have 2, 280 motors in Abdiel so will have to see about speed, her max speed is 40 knots, so 22 secs/100ft if she's too fast I may have to get an ESC.
     
  5. froggyfrenchman

    froggyfrenchman Well-Known Member

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    All
    We have found that when shimming the pump outlets down on the boats that have come in from the fast-gun club, the occurence of pump-outlets getting clogged up has increased.
    So we shim down the outlets as a last resort.
    Keep in mind that to shim down an 1/8" outlet is not as troublesome, as shimming down the smaller 3/32" outlets.
    Mikey
     
  6. froggyfrenchman

    froggyfrenchman Well-Known Member

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    In big-gun, they generally have larger outlets, but less powerful motors.
    This leads to less chances of a clogged pump outlet, and less current drain. So longer time on the water for any given battery.
    Mikey
     
  7. Bob Pottle

    Bob Pottle Well-Known Member

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    Armored cruiser Black Prince has had less powerful motors installed, replacing a pair of Mabuchi 380RHs that required drag discs to slow it down to its IRCWCC speed. The new motors are only 3/4 as long and have a lower rpm, so I'm hoping they'll push her along at 38 sec/100' or less.

    If Monday's speed test goes OK the same type of motor be installed in the Minotaur, which is 1" longer, and 1.5 lb. heavier than Black Prince.

    Tomorrow I'll finish and test a new pump outlet restrictor that should bring the armored cruisers' pump output within the allowed limit.

    When the Black Prince and Minotaur are done HMS Gorgon and HMCS Prince Robert will be converted. Their pumps are OK so they just need to be slowed down. They already have low powered motors so will probably have to run with only one powered shaft and a drag disc.

    Our first fleet battle is tentatively scheduled for next weekend but may have to be delayed 2 weeks to allow everyone to finish converting their ships to Treaty stats. If no other ships are ready by the 10th Ralph and I may battle against each other with the 2 armored cruisers. It's going to take some practice to fire only 2 BBs per second!

    Bob
     
  8. crzyhawk

    crzyhawk Well-Known Member

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    Are you using MAG throttles or ESCs? If you are using ESC's, you should be able to adjust your speed down pretty easy. If you're running MAGs have you thought about taking some pitch out of your props? That's what I ended up doing with my direct drive Invincible to get her on speed, and it worked pretty well for me.

    Something else I have seen people do to two shaft ships is add drag disks right before the prop, and seen one guy put his drag disks at the base of the shaft. I'm not sure if either of those options would be appealing to you but might be worth a shot.
     
  9. Bob Pottle

    Bob Pottle Well-Known Member

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    Thanks Mike,
    I don't use ESCs because even the "waterproof" ones die when damp, are not cheap and generate a fair bit of heat. (I have an excellent one for my 1/72 scale sub.) The guys in NABS who tried them seemed to have repeated ESC failures. Some said to be waterproof weren't.

    I've been able to get speeds very close for IRCWCC by using different prop sizes, different numbers of blades, and/or drag discs right before the props. The challenge is the much slower Treaty speeds, which require low powered motors.

    I think the new set of motors will be OK, and possibly too slow. In that case I can try 4 blades vs 3, or a larger prop size.

    Trying to make an intermediate size pump outlet restrictor between 1/8" and 3/32" is not going well so I may follow Mikey's suggestion and use less powerful motors for the pumps.

    Bob
     
  10. Bob Pottle

    Bob Pottle Well-Known Member

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    The latest pump test with the less powerful can motor (same diameter as a 380 but 3/4 as long) was not a success. The impeller was attached with silicone because I'd run out of CA, and it came loose several seconds into the test. The initial pump stream was puny compared to that from a 380RH motor so output was far below what's allowed.

    I'll buy more CA tomorrow and retest, but will either have to go with a larger outlet (3/16" vs 1/8") or go back to the 380 motor and drill out a 3/32" restricor to 7/64", which should put the output close to the allowed max of 3/4 US gallon/minute. Hope to get the pump issue solved this weekend.

    Ralph and I plan to run speed trials on the two armored cruisers Sunday afternoon.

    Bob
     
  11. Bob Pottle

    Bob Pottle Well-Known Member

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    The new props arrived for Black Prince and Minotaur and were installed tonight. Their smaller size (25 vs 30mm) and much smaller blade area should significantly reduce the ACs' speed despite the increased rpm with the smaller props.

    The 20mm props are too small for the armored cruisers but should be OK for the Gorgon and Prince Robert, which weigh less than half as much.

    Due to the forecast of bad weather all weekend in New Brunswick I may cancel the cottage visit and try to complete the speed trials here between downpours.

    Bob
     
  12. HMCS

    HMCS Active Member

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    Abdiel is running about a second slow. Will have to switch to 4 blade props or move up to 1" w/ same pitch and blade count.

    I also ordered Conyway's 1906-1921 and 1922-1946. 153 dollars for both of them brand new from amazon.com(including shipping by 1-3 day courier)
     
  13. Bob Pottle

    Bob Pottle Well-Known Member

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    Scott,
    Based on last weekend's trials of the Black Prince, Abdiel's 280 motors will probably slow down so much with a 4th blade that the speed will drop instead of increase.

    Running BP on 3 blade 30mm props gave a speed of 25 secs/100'. Using 4 blade 30mm props dropped the speed to 30 secs/100'. The motors' rpm dropped so much with the higher drag of a 4th blade that the additional blade area was of no benefit and decreased the speed.

    Switching to different 3 blade 30mm props with smaller blades dropped the speed to 27 sec/100'.

    You'll probably be better off fitting a slightly larger prop with the same number of blades. On the other hand being 1 second too slow may be as close as any of us get in converting to Treaty speeds. I'd be inclined to go with what you have now.

    Bob
     
  14. HMCS

    HMCS Active Member

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    Thats what I was thinking Bob, Abdiel will be the fastest boat on the water even at 1-1.5 seconds slower then allowed speed. I ordered a set of 1" props with same pitch and blade count to play around with,as well I do have Speed 300 motors and BC 365's on hand.
     
  15. Bob Pottle

    Bob Pottle Well-Known Member

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    Ah, we'll eventually get all the ships compliant. For now I'm not concerned if the speed's are a little off. It's going to be hard enough to fire at a "one, one...(fire).. thous-and (fire)" rate!!

    Bob
     
  16. HMCS

    HMCS Active Member

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    Yes, it would seem that 2 shots a second would be easier then 1 shot ever 1/2 second.