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Author Topic: Voltage for 700 motors?  (Read 2461 times)

aln101boat

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Voltage for 700 motors?
« on: November 26, 2015, 03:16:11 PM »

Hello there,
Building a 48" huntsman 31. (Precedent wooden kit).
Bought two 700 motors originally intending to run them from 6v 8Ah Cyclon cells.
They don't sound very interested running free on the 6v sla. This caught me unawares as 545s in another boat scream on the 6v cyclon
A bit better on 7.2 NiCad.
Howl on 12v sla.
A bit difficult to judge till they are fitted and loaded on my choice of either 45mm or 50mm props, but do you think I should be aiming at 12v supplies?
I really need to make up my mind early, as weight is going to become an issue if 12v
rgds Alan
 
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Tug-Kenny

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Re: Voltage for 700 motors?
« Reply #1 on: November 26, 2015, 03:28:12 PM »


Please pardon my ignorance but what are  Cyclon  cells.

If they are not too big then perhaps you run two in series for 12 volts.

Cheers

ken
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Netleyned

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Re: Voltage for 700 motors?
« Reply #2 on: November 26, 2015, 03:56:08 PM »

Please pardon my ignorance but what are  Cyclon  cells.

If they are not too big then perhaps you run two in series for 12 volts.

Cheers

ken


Posh SLA's Ken.
They come in 2V units to make up as 6v or 12v or any multiples of 2.


Ned
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aln101boat

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Re: Voltage for 700 motors?
« Reply #3 on: November 26, 2015, 04:40:51 PM »

Cyclon cells are lead acid, but the plates are like a swiss roll. Very strong construction resistant to warping. Able to take abuse both discharging and charging. Very high discharge rates available, well over 100 amps.
American company, but available pretty much worldwide as individual 2v cells up to 25Ah, or in cased blocks of 2, 3, or 6 cells up to 8Ah.
Seem to be not as easy to come by recently, when searching on Ebay.
Some might be aware of them in motorsport, as full sized batteries. Usually orange. Recognisable by the six visible cylindrical cell shapes.
rgds Alan
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inertia

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Re: Voltage for 700 motors?
« Reply #4 on: November 26, 2015, 04:54:37 PM »

There are (or rather were) several different types of 700 motors. Do yours have any identifying labels?
I think my opinion about running a Huntsman on any sort of lead-acid batteries is too well-known to need repeating.
DM
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aln101boat

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Re: Voltage for 700 motors?
« Reply #5 on: November 26, 2015, 07:11:22 PM »

There are (or rather were) several different types of 700 motors. Do yours have any identifying labels?
I think my opinion about running a Huntsman on any sort of lead-acid batteries is too well-known to need repeating.
DM
The 700s came from the Anglia Model Center. 70068 seems the most obvious number on them. Has a fan and looks like 5 poles. Oh, and a sleeve/band round it which I think has something to do with torque.
Can you give a link or point me towards your thought on huntsman's and lead acid. I'd be interested.
rgds Alan
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Colin Bishop

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Re: Voltage for 700 motors?
« Reply #6 on: November 26, 2015, 07:52:40 PM »

I have Cyclons (8v and bought years ago) in my unfinished fishery cruiser but I don't think they would be the right choice for a Huntsman given the variety of high capacity NiMH cells available these days. You can only safely discharge lead acids to around half their nominal capacity but you can virtually drain NiMH packs so you actually get a lot more running time for the same nominal capacity.

Colin
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aln101boat

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Re: Voltage for 700 motors?
« Reply #7 on: November 26, 2015, 08:19:20 PM »

Ok DM. Found it. You are quite correct in all you say about lead acid (gel being the worst for dropoff at anything more than a few amps). Cyclone's are the exception.
The remark about ballast was valid though. The Faireys, although fast, were heavy boats for their size for good reason. Their seekeeping was a product of that weight.
Most of the video I've seen of huntsman models show them behaving quite unrealistically because they are too light. Usually IC, I have to admit.
I've estimated that my model could be around 8Kg, or slightly more, displacement on the correct draft marks. Anyone actually knows, give me a call.
The boat (I've added a lot of extra wood in its construction) comes in at 4Kg.
Motors, shafts, rudders, ESCs are just over a Kilo.
Leaves 3Kg for batteries.
Alan
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derekwarner

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Re: Voltage for 700 motors?
« Reply #8 on: November 26, 2015, 08:24:17 PM »

Cylon cells [2v lead acid] were manufactured by the Gates Corporation in the UsofA

They were actually used in Oberon Class submarines in banks of 55 & the cells were encased in rubberised surfaced rectangular box filled with a tar like substance........

[not to be messed with.....each E type cell had an open circuit current discharge of 665 amps   :kiss:]

If one cell went O/C, the complete bank was deemed as reject O0...[some keen model boat builders did try to remove some of the good cells from the reject banks, although found this near impossible without damaging the outer tubular steel case of the cells >>:-( ]

Did any of our Sub Mariner members serve on Oberons?........Derek

http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiEj5eF9q7JAhWi4qYKHSRDC98QFggdMAA&url=http%3A%2F%2Fwww.digikey.com.au%2FWeb%2520Export%2FSupplier%2520Content%2FEnersys_842%2FPDF%2FEnersys_Cyclon_SelectionGuide.pdf&usg=AFQjCNELb5l0wXbzKOyjyl-OsuYUzpKMkg
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jarvo

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Re: Voltage for 700 motors?
« Reply #9 on: November 26, 2015, 09:18:09 PM »

HI Alan


My thoughts are use 6volt NmHi cells in series 12volts each motor, as an alternative LiPo cells 11.6 volts per motor but use a voltage alarm to stop over discharge.


My Huntsman is the 34 inch version single motor, graupner 750, goes like stink on 2 4ah 6v gel cells but it is heavy, on NiMh it bounces over the water, in the process of changing to a brushless motor still on the NiMh batteries


Hope this helps


Mark
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inertia

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Re: Voltage for 700 motors?
« Reply #10 on: November 27, 2015, 08:56:24 AM »

Ok DM. Found it. You are quite correct in all you say about lead acid (gel being the worst for dropoff at anything more than a few amps). Cyclone's are the exception.
The remark about ballast was valid though. The Faireys, although fast, were heavy boats for their size for good reason. Their seekeeping was a product of that weight.
Most of the video I've seen of huntsman models show them behaving quite unrealistically because they are too light. Usually IC, I have to admit.
I've estimated that my model could be around 8Kg, or slightly more, displacement on the correct draft marks. Anyone actually knows, give me a call.
The boat (I've added a lot of extra wood in its construction) comes in at 4Kg.
Motors, shafts, rudders, ESCs are just over a Kilo.
Leaves 3Kg for batteries.
Alan
Alan
Cyclone cells, as you know, are a rare beast. Colin Bishop has had some difficulty in finding a suitable charger for his. My objection to SLA's relates to the familiar brick-sized monsters which will turn a fast planing cruiser into a plodding canal narrow-boat. As Jarvo says, if they prove too heavy then there are two obvious alternatives but I'd say go with what you have before you shove your hand into your wallet pocket.
That aside, are you absolutely certain that what you have are 700-sized motors (44-45mm dia)? If so then they will probably be far happier with 12v than anything less (certainly not 6v), especially if they have 5 poles. You should be aiming for a no-load speed of 11000+ RPM, although anything more than about 15,000 would be too much. If you use plastic props to try the model out then buy some X40, S45 and X45 sizes. That means using six of your (2v) Cyclone cells.
My little 1/16 scale Huntsman weighs just about 1kg; sits dead on the scale waterline, and planes just right at about 3/4 top speed - that's according to the Fairey Owner's Club. Using the "cube" rule then your calculation of 8Kg for the 1/8 scale on is about right (2 x 2 x 2). The reasons why so many videos of Huntsman models show them twitching and skipping round the pond are that many are overpowered and the helmsmen seem to regard the rudder stick as more of a switch.
DM
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aln101boat

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Re: Voltage for 700 motors?
« Reply #11 on: November 28, 2015, 09:39:27 AM »

Hello Mark and DM,
Thanks for that.
    I use the 7Ah SLA bricks for various other things. They certainly are BRICKS.
Looks like I'll be aiming at 12v then. I've got a couple of 6v 5Ah cyclons, so I can try these on longer leads to sort out the weight distribution once it floats.
I'm fairly sure it will need some weight in both ford and aft cabins.
   Was looking at 9Ah nicad "D"cells in the Component shop. Might be the answer but 75 and I can split up the ten of them in any ratio if necessary to trim the boat. Same end price as the 8Ah cyclons, but a lot lighter.
There were also "F" cells at 13Ah :-)) . Don't think I've heard of "F" before, but they'd be 120 <:(
rgds Alan
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inertia

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Re: Voltage for 700 motors?
« Reply #12 on: November 28, 2015, 10:54:48 AM »

Alan

If you've mounted the motors in the front cabin then you'll need most of the weight at the back. We had to screw a couple of lead blocks to the transom frame to get the prototype H31 (47") to plane properly with its I/C motor. The single battery pack in the little model (a 3S 2600maH LiPO) sits directly underneath the cockpit floor and the model needs no further ballast.

Do try to keep the leads between the battery packs short. This will minimise any voltage drop and reduce the effect of the cables as RFI transmitters. It's also cheaper!

Before you decide on higher-capacity battery packs you'd best be advised to stick a watt-meter into the circuit of each motor and run the thing on the water. This will tell you the maximum current drawn. You need then to check the maximum current available from the proposed batteries. Some of the very large NiMH packs are relatively quite low in this respect (and you can't charge them any faster than C). Here's the meter I have http://www.4-max.co.uk/wattmeter-budget.htm although you could probably get a similar one from China for a very silly price.

DM
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aln101boat

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Re: Voltage for 700 motors?
« Reply #13 on: November 28, 2015, 10:09:50 PM »

Alan

If you've mounted the motors in the front cabin then you'll need most of the weight at the back. We had to screw a couple of lead blocks to the transom frame to get the prototype H31 (47") to plane properly with its I/C motor. The single battery pack in the little model (a 3S 2600maH LiPO) sits directly underneath the cockpit floor and the model needs no further ballast.

Do try to keep the leads between the battery packs short. This will minimise any voltage drop and reduce the effect of the cables as RFI transmitters. It's also cheaper!

Before you decide on higher-capacity battery packs you'd best be advised to stick a watt-meter into the circuit of each motor and run the thing on the water. This will tell you the maximum current drawn. You need then to check the maximum current available from the proposed batteries. Some of the very large NiMH packs are relatively quite low in this respect (and you can't charge them any faster than C). Here's the meter I have http://www.4-max.co.uk/wattmeter-budget.htm although you could probably get a similar one from China for a very silly price.

DM
I've stuck as close to the real boat as possible, in which the engines and fuel tanks were the largest single weights.
Motors are in the correct place in the engine room (under the aft two thirds of the cockpit) which gives the correct shaft and prop alignment. They are only half the scale weight though, so to make this up it will probably need a little bit of weight in ford cabin, and majority in aft cabin. I'll muck about with the two cyclons at first just to see how wild the trim might be.
Comments on the larger NiMh's discharge rates is appreciated as I hadn't expected that, and I looked up the meter you mentioned. That looks a lot simpler than the temporary jury rig I was intending.
Thanks again
Alan
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