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Author Topic: los angeles class 1/80th scale static diving rc submarine  (Read 27095 times)

triumphjon

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #50 on: May 24, 2012, 08:12:44 am »

those two small servos look very close to the main drive motor ? hve you got lots of superssors on th motor ?  id have thought brushless motors would be better fitted here , as they run more efficiently than the brushed ones  ?
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Subculture

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #51 on: May 24, 2012, 08:24:51 am »

Good stuff.

Make your baffles cylindrical, so they fit inside the tank with just a very small gap between the edge of the baffle disc and the cylinder wall. If you want a cheap (free) material that's easy to cut, have a look for an abandoned estate agents 'for sale' sign. These are made from a corrugated plastic, which is strong but light, waterproof and easy to cut to size with a knife. I would put three baffles in that tank, as it's quite long.

I'm a little concerned about the ballast tank endcaps (coffee jar lids?). Pressures will reach 50-60psi (4 bar) on a sealed system, so it needs to be strong as you will have several hundred pounds acting against those walls. I'd recommend using some plastic sheet at least 3/8" (8mm) thick tied together with two or three metal rods, and securely bonded into the cylinder at each end. If you get a chance to look at a sheerline or Eden boat, you'll see the tank is of very sturdy construction, and it's not done for fun. Copy it.

It looks like you have a direct drive 500 size motor for power. I see it's MFA, and from memory they do about 1000RPM per volt. At 12 volts this will be far too high revving for the size and pitch of prop you have on this boat. You can gear it down 4 or 5:1, or use a lower revving motor. The former is going to require you to move the servos back a bit to allow for the gearbox, the latter may be tricky to source. I would think you'll want a shaft RPM of between 2500-3000 RPM and motors with those specs tend to be indistrial quality (Buhler, Maxon etc.) and take a little hunting down. Brushless motors are nice, but not really necessary plus they'll push the price up considerably.

I have a feeling the waterpump you are using will corrode- designed for pumping fuel, not water.

BailingBen

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #52 on: May 24, 2012, 10:39:56 am »

the motor cant be changed as its bracket is heavily glued to the wtc so to replace would need a whole new end cap the coffee lids arnt moving they where epoxy and silicone in and i didn't go light on either of them this also means i can add/take any baffles out but i am sure two will suffice  the geared motor is second hand its a water one but not sure if its been used before in the test it was fine   cant do brushles do to cost


                                                                  kk

ps: this is my first proper sub i can guarantee im going to make mistakes  and after this i want to build a vanguard from deans marine as its a similar size and hopefully i wont make the mistakes i make on this on that
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triumphjon

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #53 on: May 24, 2012, 02:30:09 pm »

kk , are you able to pressure test the tank other than filled with water ? it would be better to alter the parts SUBCULTURE  has pointed out now rather than have a problem later , ive accsess to a lathe and milling machine if something needed changing !
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Subculture

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #54 on: May 24, 2012, 04:14:08 pm »

It's not the bond I'm concerned about, it's the thickness and strength of the coffee pot lids. The ones I've encountered are usually rather thin, and brittle plastic. Good enough for their original purpose, but not what you want for a part that has to with stand quite a bit of pressure.

The screw on an LA class at 1/80 scale is going to be about 3" diameter. I don't know the angle of attack of the blade, but I think it's a Raboesch prop you have, and they tend to be a 'square', so we'll say 3" pitch or thereabouts. Even at 3000RPM your boat will be doing about 6 knots. If the motor is stuck in, cut it out, because it isn't going to work as is, at best you'll overheat the motor, perhaps your speed controller too. You should be able to take the motor in and out easily anyway, as you need to service the shaft seal and motor bearings periodically.

triumphjon

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #55 on: May 24, 2012, 08:30:17 pm »

sub , having met kk at the lakeside this afternoon i would hope hes learnt silicone sealant motor adhesion isnt quite as secure as he originally thought ! id much rather over engineer a biuld & not have future problems
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Andyn

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #56 on: May 24, 2012, 09:22:52 pm »

The prop on that thing is a 60mm 7 blader :-)
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Subculture

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #57 on: May 24, 2012, 10:16:16 pm »

A bit smaller than I thought it would be. All the same you shouldn't need more than about 3-3500RPM for lively performance, you have a lot of blade area on that prop, and the LA class is a slippery hull that doesn't need a lot of poke to make it slide through the water nicely.

BailingBen

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #58 on: May 24, 2012, 11:35:52 pm »

i think i will keep my motor as its a slow 480 and shouldnt be that bad the blade is propshop and the coffe lids will be filled with epoxy then smoothed with filler that should give it more than enough strength   


                                                         ta kk
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Andyn

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #59 on: May 24, 2012, 11:46:34 pm »

If it's the same prop Rich had on there, it's the same prop I bought, and it's a Raboesch 60mm 7 blade, from Steve Tranter.

Straight drive that prop will destroy a 480 in seconds.
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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #60 on: May 25, 2012, 07:12:52 am »

It's a 480!! Yikes, I thought it was a 500 size motor, which was pushing your luck. No chance kiddo, not in a millions years will a 480 pull that size prop direct drive.

But it's alright- free entertainment is not to be sniffed at these days. Now, where's that popcorn?

essex2visuvesi

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #61 on: May 25, 2012, 07:28:19 am »

i think i will keep my motor as its a slow 480 and shouldnt be that bad the blade is propshop and the coffe lids will be filled with epoxy then smoothed with filler that should give it more than enough strength   


                                                         ta kk

You are so gonna cook that motor or burn out the ESC even if its a slow one... you are doing the equivalent of putting the engine from a ford fiesta on a tractor
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BailingBen

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #62 on: May 25, 2012, 05:27:34 pm »

sorry got it wrong  i have a mfa 540/1 low drain motor





ta kk if it explodes i will replace but not until it does i may run the motor of a 6v batt and everything else off 12 v
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BailingBen

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #63 on: May 25, 2012, 05:31:32 pm »

and the prop is babosh or whatever itas called lol
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Subculture

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #64 on: May 25, 2012, 05:38:45 pm »

Okay, that motor does 15000RPM or thereabouts at 12 volts. At half the volts it's still running much too fast.

You want it geared down about 4:1 or 5:1 for use on 12 volts, or about 2.5:1 on 6 volts, then you can be assured it will work well with that prop.

BailingBen

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #65 on: May 26, 2012, 01:00:05 am »

the isuue i have is room i have none of it left especialy llength ways so will have to see how it goes im using an electronize esc so can adjust full throttle
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triumphjon

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #66 on: May 26, 2012, 08:07:14 am »

kk , some of the aero modellers use inline gearboxes which mount directly on the front of the motor ,  we can always turn up a solid coupler that wont take up as much space as the huco type you normally use ? there is no point ploughing on with your build only to HAVE  to replace a motor when it fails five mins after its got into the lake ! . reckon you have plenty of space if you were to use it wisely
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BailingBen

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #67 on: May 26, 2012, 08:32:21 am »

i havev no space left the wires are pushing against the endcaps the pump only just fits on the end if you saw it you would see no room !
i can adjust max throtle and v of batt so will be ok and i have a mmb solid conector wich sits inside the waterproof holder thingy will showyou when i see you later
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essex2visuvesi

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #68 on: May 26, 2012, 08:35:51 am »

Triumphjohn

I have to commend you on all the help you are giving KK.  It's nice to see someone going out of their way to help a young'un :)
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BailingBen

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #69 on: May 26, 2012, 08:50:58 am »

YES THANKS JON ALL APPRECIATED     also we have unbuiltnautilas who gave me the pump the wtc alot of advice the valve (green thingy)
a discount at the modelshop and lots of lead and other bits and bobs needed
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Andyn

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #70 on: May 26, 2012, 11:31:12 am »

A 555 motor would swing that prop easily, that's what I bought it for...
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Subculture

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #71 on: May 26, 2012, 02:29:40 pm »

Those are a low RPM 600 size motor aren't they? Certainly a better bet than what he has in there, a little more RPM than is needed really, would be better if the motor did about 4K unloaded rather than closer to 5K.

Andyn

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #72 on: May 26, 2012, 02:52:28 pm »

It'll do about 4500 on 12 volt when loaded, would be absolutely perfect. Tons of torque in them too.

As it happens, I've got three brand new unused ones for sale...
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triumphjon

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #73 on: May 26, 2012, 04:00:54 pm »

gents , i know kk is on a limited budget , would fitting a torque ring on his existing motor help bring the revs down ?  i think with a little more planning and a replacement mounting board space wouldnt be such a problem !
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Andyn

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Re: los angeles class 1/80th scale static diving rc submarine
« Reply #74 on: May 26, 2012, 04:21:00 pm »

Nope, it'll still be far too fast...

I don't know how that mount was put together, but I designed it so that the motor can be removable afterwards, just undo the bolts, pull the motor out until you see the first grub screw, loosen that off and it'll come out.
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