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Author Topic: short run time  (Read 4975 times)

Shipmate60

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Re: short run time
« Reply #25 on: June 08, 2008, 02:19:52 PM »

John,
If they are true 540's they will only take 7.2 Volts so 12 might burn them out.

Bob
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John W E

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Re: short run time
« Reply #26 on: June 08, 2008, 02:53:04 PM »

hi there

Bob; I wonder if these 540 motors that have been supplied by RS are the ones they were 'selling off' not so long ago; as a 6-18 volt 540.  They were originally made for the battery-operated drills; I do not think that these 540s have the fan in the commutator end.   In actual fact, they were a 12-18 volt motor; cheap and nasty things from a foreign source.  Maybe wrong....but, .... maybe right  O0

aye
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bluebird
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FullLeatherJacket

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Re: short run time
« Reply #27 on: June 08, 2008, 05:57:53 PM »

Have a look at this, chaps - straight from Mabuchi's own website. BTW the RS is a manufacturer's nomenclature and nowt to do with Radio Spares/RS Trade.

http://www.mabuchi-motor.co.jp/cgi-bin/catalog/e_catalog.cgi?CAT_ID=rs_540rhsh

Looks pretty hot for direct-drive on 12v, doesn't it? Still, it shouldn't be drawing umpty-squat amps. I've still got my money on the power supply or charger being crook.

Surabaya - you asked about "Soft"; the 3-pole Sun 540 which we stock is rated at a nominal 7.2v; RPM at Max Efficiency is 8390 and current 4.04A. Torque is 223g.cm. It's all relative, but that's pretty soft for a 3-pole motor in this size of can.

FLJ
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Martin [Admin]

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Re: short run time
« Reply #28 on: June 08, 2008, 06:46:50 PM »

Can any you clever cloggs give me a brief guide to reading these motor charts please....... :'(
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HS93 (RIP)

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Re: short run time
« Reply #29 on: June 08, 2008, 06:55:48 PM »

if you go to the original link and play in shockwave. it's interesting to see the efficiency drop as the temperature goes up

Hs93
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John W E

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Re: short run time
« Reply #30 on: June 08, 2008, 07:57:05 PM »

hi Surabaya

Looking at the link - the one that the Man from DelMonte has put on here  O0 - your RS540 SH motors in your model are from 6 to 12 volt & they do 17thousand&something ....  :) rpm at 12 volt so therefore, with you having yours wired in series - they will only be doing 8000-9000rpm each.  This will account for the slow performance.
Also, I think you may not have charged your battery fully, giving the poor performance on duration.

So...fully charged battery - anywhere between 24-36 hours - at 600 ma 

rewire your two motors into parallel - ensure that your speed controller can handle, because, at 12volts under load, they say about 6 amps per motor.   So, to be on the safeside, let us hope your speed controller can handle 20-24 amps.

To be really, really safe, fit a fuse of say either 10 or 15 amps between your speed controller and your battery.

aye
john e
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surabaya

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Re: short run time
« Reply #31 on: June 08, 2008, 10:06:18 PM »

Hi, all.
Martin, now you`ve really gone and done it. That`s not a "scribble", thats a page out of a fizzysist type book. ??? :-\ :o I get confused with the beano. ;D
I think I am going to go the route bluebird suggests. Sounds like a safe bet.
Plus I like the "scribbles"
Thanks to all for the help and I will let you know next weekend if it sinks or swims so to speak.
Ps I do no ow to spewl  :D
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surabaya

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Re: short run time
« Reply #32 on: June 16, 2008, 10:34:16 PM »

Hi,
I rewired the boat motors in parallel as suggested and tried it. It did not seem much faster, but after a few minutes it slowed, so I brought it in. When I checked inside, the battery was very hot and the Esc warm. I tried the motors, still in the water and they almost stopped due to low battery, I think the battery is naff.
I thought I would change the wiring back and give the other battery a try, it is a 12v 4ah.
This time I had more success. I stopped to check and all seemed fine, so I continued and had a good 30 - 40 Min's before it started to set a little slower.

The only problem is that when I brought it back in, the motors were red hot although the Esc was still only warm.
I have a feeling that the answer maybe to dump the old battery and change to a little bigger motor.
Any suggestions? not too costly. 850`s seem a little pricey for a pair at the moment.
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Shipmate60

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Re: short run time
« Reply #33 on: June 16, 2008, 11:53:35 PM »

The cheaper option would be to go for 550 motors, but the original Mabuchi, not the Chinese ones.
And certainly NOT the Jonson motors.
Unfortunately these days they are like hens teeth to find but will happily run on 6 or 12 volts.
What size props are they on her?

Bob
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Shipmate60

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Re: short run time
« Reply #34 on: June 16, 2008, 11:59:36 PM »

here is a pic of my old gunboat at about 3 feet long running on 1 x 550 and a 3 blade 35mm prop shop prop.
She is running on 8.4 Volts on 2Ah cells which used to run for about 30 mins.
Bob

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malcolmfrary

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Re: short run time
« Reply #35 on: June 17, 2008, 01:04:09 PM »

If it performed OK with a good batery, but the motors got hot, why not consider water cooling the motors rather than changing them?
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John W E

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Re: short run time
« Reply #36 on: June 17, 2008, 03:32:22 PM »

Surabaya hi there

Just reading the results of your last trial of the boat.

It has brought me to a couple of conclusions:

If we take it one at a time:

Look at your actual model - it is actually based on a sort of leisure/broadstyle cruiser.  The original boat is Not really designed and built for speed.  We should then be looking for a speed slightly quicker or just around walking pace, not that of a 'blistering' fast MTB or an offshore power boat  ::)

So next we will look at how your model was made.   It looks to be of a fairly heavy construction - frames made from thick plywood; and so forth.   So, the hull itself will weigh a fair amount.   Plus the hull shape does not lend itself to be one of a fast boat.   What I am getting at now is, by increasing the motor and propeller size is not really going to gain you much in the way of speed.

You have said that you went to a 12 volt 4 amp battery and also, you rewired your motors from parallel back to series.  You got a better duration time from this set up.  To me, this indicates that although the motors are rated between 6 and 12 volts; they are at their happiest running at a 6 volt because that is what you are doing when you wire them in series from a 12 volt battery - each motor is receiving 6 volts.  So, with this in mind, why not invest your money in 2 x 6 volt batteries - of either 4 amps or the 8 amp variety.  Where you could place 1 battery between your propeller shafts at the rear half of the hull and this would dispense with some of the lead weight that you have been putting in that area and also, place the 2nd battery forward where your original battery was situated.   Then, wire both batteries up in parallel giving you 6 volts but double the amperage if you used 2 x 4 amp batteries it would give you 8 amps.   If you use 8 amp batteries it would give you 16 amps.

As well as doing that, rewire the motors up again in parallel so that each motor individually receives 6 volts - this should give you the same or better running time for less cost than it would be to re-motor it, and add new props on.

To be honest with you, I don't think you are going to improve much on the model's performance.  If you really want a model to perform as a speedboat they tell me they are selling Concorde's engines off pretty cheap.   Downside to that though, fairly large consumption but boy will it make your boat go.

Have you ever thought about building a new cabin cruiser from a set of plans or one of the semi-kits you can purchase.

I know there are several people on this Forum now who have said they couldn't manage to build from plans, but I know they are well on their way building now.....and it was not as difficult as they thought it was.

This would give you the opportunity to build a model with a higher speed performance than your existing one.

aye
john e
bluebird
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surabaya

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Re: short run time
« Reply #37 on: June 17, 2008, 11:09:27 PM »

Hi, All.
After the run on sunday, I was reasonably happy with it.
You are right, it is more of a broads type cruiser, I just worried about the motors getting hot and thought that maybe a little better motor would run cooler and longer plus give me a little extra speed just to have that bit in reserve.
 I run it at the local canal/ river and some people have got bigger boats than me, 30 foot bigger, Most are very nice and stop to talk or look, but some can be a little unfriendly.
I have found a couple of matching car aerial motors that I will test for amp`s.
But I think the twin 6v batteries and water cooling will help too.
If any one has a plan of a cruiser, I would be grateful ::) , but it needs to be the type that you just copy onto wood and cut out, if you  know what I mean. Has this type of plan got a special name?
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