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Author Topic: Running time guestimate...  (Read 945 times)

chas

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Re: Running time guestimate...
« Reply #25 on: July 17, 2019, 02:54:41 PM »

Hi Richard, I refer you to my third post, understanding these things will save you money and heartache later. Anyway you seem to have placed an order so here's hoping you're happy with the result. Four things come to mind immediately.
1. You don't mention a lipo charger, I presume you have some way of charging them when they arrive.
2. I hope you checked delivery is from UK or European warehouse, you might get hammered for tax otherwise.
3. Propeller size, since you seem to be aware of how brushed motors work, it's just the same for brushless. I.e a large prop needs more power ( amps) to turn it. So reducing the propeller size will reduce the power needed and give a longer run time.
4. Did you read some of other peoples ideas and installations from the search box I mentioned? There's a lot of good ideas and experience there.
  Lastly, and not related to your order, making a Perkasa turn well can be addressed by experimenting with rudder shape, but most effectively by using a mixer to allow the motors to help. But that's for later, if you feel you need to go down that route.
 Chas.

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Richard Houston

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Re: Running time guestimate...
« Reply #26 on: July 21, 2019, 05:25:42 AM »

ok, lets begin ...


1. Yes I own a HTRC HT100AC/DC Smart Charger is brand new so all good for lipo charging, I also got a stand alone balance board for it as the one that comes with it is ok but a bit flimsy I thought.


2. Everything is from the UK apart from the Motors, both of them are from Hong Kong and yes I got stung on import duty tax but more money than sense so no big issue motors will be here tuesday ... See below.


3. I'll change this if I need too but as its got a nice sized racing prop on right now i'll try this first and will change if need be.


4. a few I have read but what I'm struggling with meantime is power cables and gauge to buy, I have 3m of the following sizes available to me on hand 14awg, 20awg for internals and 24awg for lighting, but since its gonna be 2x 4S lipo running the motors and ESC's If i need better gauge like 8AWG i'll get that, 14.4v

5. Something not really touched on just how big of a ESC would this setup require





As another poster posted, Moving from Torpedo 800's to the 350Kv is one thing but I noted its going from 6mm shaft to 5mm shaft would I need to order new Couplings to be on the safe side and do they just come in one size fits all ?
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malcolmfrary

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Re: Running time guestimate...
« Reply #27 on: July 21, 2019, 11:29:11 AM »

Wire size - look at the battery wire.  Thats as heavy as you will need.
Coupling size.  One size does not fit all.  Various size options are available, with different ways of getting the combination needed depending on the make.  Some are rigid one piece items with the right size hole at each end, some are three or more pieces with a selection of end pieces to match motor and prop shaft, with your chioce of bendy bits in the middle.  Some are closely related to the solid type, but have the end pieces selected to order with the flexible bit in the middle ready fixed.
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jaymac

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Re: Running time guestimate...
« Reply #28 on: July 21, 2019, 12:24:58 PM »

There is a  large list of prop and motor details over on the other site  https://www.modelboats.co.uk/forums/postings.asp?th=45505&p=4  scroll down about 4-5 posts. Richard you may already know this but scale speed on your boat is only about 10 mph.
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Richard Houston

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Re: Running time guestimate...
« Reply #29 on: July 25, 2019, 01:01:09 PM »

What will be interesting is the run time of 2x 5000mah 4S 40C Turnigy lipos through a 2x Turnigy Marine 70A ESC running to 2 of these motors ... 2x Turnigy Aerodrive SK3 - 4250-350KV


I know 60mm 2 blade Sports Prop


Just a guess would be nice as the boat is still in the building phase
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RST

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Re: Running time guestimate...
« Reply #30 on: July 25, 2019, 11:35:31 PM »

Richard I think you're asking a good question.  For me your props are just huge for that hull (surprised nobody else commented) and I worry why one is painted green and 'tother red but hey ho.  If it were me I'd knock them back to something more like 40mm'ish.


I just did a similar thing to you in as much as bought 8.4v Ni-MH 5Ah sticks for my Sangsetia.  I bought motors for it so long ago I can't remember now but it was based on 12v SLA which was too heavy.  I'm old school brushed though.  I will put it in the bath and do a test to see how it goes, nobody can really give a definitive answer -I think you can wait for a week or a month if you don't try yourself.  Trying for yourself is part of the fun.  And If you're lucky enough to sail with the guys in Duthie Park, sure they'll let you re-charge batteries betwen sailings.

Rich
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Richard Houston

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Re: Running time guestimate...
« Reply #31 on: July 26, 2019, 12:33:05 PM »

Port and Starboard props hence red and green, they came like that so I wont forgot which was which.


Also to compensate for the weight change moving from torpedo 800 motors to lighter more powerful brushless motors and also moving from Solid lead acids to lipo's I've made a new bracket to hold the motors in place out of mild steel, so this very much does compensate the weight and also hold the weight more centred in the boat


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