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Author Topic: What Motors,  (Read 4659 times)

wullie/mk2

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What Motors,
« on: February 24, 2011, 11:53:39 am »

Hi,guys,I,ve got an MFA Tracker,its fitted with 2 x 800 motors,..i want to replace these as i feel they are not suited for this model,what alternative motors could i fit,..I don,t want to go up to the 850,s as these are very expensive,for me,coupled with the fact that when using 12v batts the weight is quite heavy,
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Lord Bungle

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Re: What Motors,
« Reply #1 on: February 24, 2011, 11:56:20 am »

800 costs the same as 850 last time I looked on fleabay mate, you could stick your 800's up for grabs and then get 850s  :-)
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wullie/mk2

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Re: What Motors,
« Reply #2 on: February 24, 2011, 12:38:24 pm »

I did consider that option,but it still brings me back to using 2 x 12v 7ah batts,..12v per motor,..and with that extra weight it just kills the playing time,...maybe its time to get rid of the Tracker and get something thats a bit lighter,
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grasshopper

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Re: What Motors,
« Reply #3 on: February 24, 2011, 04:01:43 pm »

You might consider going to Lipo's  - they can supply a lot more energy for a lot less weight.

I have been using some hard cased 2s 30c 5000mAh 7.4v packs from Hobbyking.com for my model truck racing - and they allow me to do at least two 5 minute races with a brushed low wind motor. Some of the guys I race are doing three heats with a brushless motor set-up.
http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11613

You could possibly drop 4 packs into your boat, giving you 14.8volts per motor for half the weight of one lead acid cell - not necessarily the cheapest route but it certainly would perform better!

I've bought from this site - before they had a German warehouse and got stung for VAT, import duties etc. Now you should only pay what your see - and at US$23 a pack that's a good price!
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wullie/mk2

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Re: What Motors,
« Reply #4 on: February 26, 2011, 11:07:46 am »

Thanks for the tip,i shall try what you suggest,as it will mean my mod will be over 6kg lighter
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malcolmfrary

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Re: What Motors,
« Reply #5 on: February 26, 2011, 11:23:19 am »

Of course. if going down the lithium road, a battery condition monitor is needed.
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wullie/mk2

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Re: What Motors,
« Reply #6 on: February 28, 2011, 11:50:39 am »

That sounds expensive,please enlighten me,
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barriew

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Re: What Motors,
« Reply #7 on: February 28, 2011, 11:58:55 am »

Wullie

If you are going to use LiPos with a brushed motor and ESC, you need to protect against discharging your battery below about 3v per cell. When used with a brushless motor and ESC the ESC offers this protection. You need something like this http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=270541150190&ssPageName=ADME:B:EOIBSA:GB:1123
although you dont need to buy fro Hong Kong - Astec sell a similar item.

As you see its not really expensive and it does work - I was using one of these on Sunday and the boat suddenly slowed, but allowed me to bring it to shore

Hope this helps!

Barrie
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Roadrunner

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Re: What Motors,
« Reply #8 on: February 28, 2011, 12:58:58 pm »

Im a bit perplexed to your issues ...

Now im not sure what your electrical setup is but i can only imagine you are running twin esc's with there own power supply which although nothing wrong with that but your over killing in battery weight for no real reason.

There are indeed ways to speed up your boat and make it lighter, far cheaper then whats being suggested in LIPOS, im not a big fan and anyone with some sense willl or really should tell you 'cheap' lipos are not really worth the cash, and since your not prepared to upgrade your 800's to 850's i have no doubt that spending £50 each for a decent lipo is also out of the question, and you have to actually have some experience with this type of battery or you really will end up having to get a new boat since yours will be a molten pile of GPR at the bottom of the lake.

Take a look at ACTions P102/3 Power distribution board, this little device will allow you to connect your twin esc's to it and run off a single 12V 7ah battery thus decreasing the weight even more and giving a better speed output. At £25 Its far cheaper then going down the lipo road to hell. Also look at the mixer unit for your esc's (P82) should you not have one already fitted.

http://www.action-electronics.co.uk/mixers.php P82 motor mixer £20
http://www.action-electronics.co.uk/pat.php P102/3 power board £25

These two alone are cheaper then 2 or 3 lipos with out chargers and other junk needed for them!

Yes your boats going to be faster, but run time will become less, but you now got 3 spare battery's at the lake side!  

Also looking at changing your prop to either something a tad smaller, or to a 3 bladed prop these little changes can make a big difference, this is the whole part of boating trial and error in some cases but  a few little things can make a huge difference.

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grasshopper

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Re: What Motors,
« Reply #9 on: February 28, 2011, 03:30:37 pm »

Your not being a fan is not an excuse for slating the use of  Lipo's - I have 5 packs of 'inexpensive' 7.4v hardcase lipos which I use (and abuse) weekly in a 1/10  model short course truck. I use the term 'abuse' loosely - I do charge them correctly in a tin box for added safety,  balance charging them every other week. I've had less issues with my £20 packs than those that use similar packs that they paid over £50  for.

All of the comments made about Lipo's are similar to those made over NicD's when they were first used for model purposes all those years ago.
If I really was going to suggest an upgrade to the OP's boat then I would also have suggested going for a decent pair of brushless motors too.

There is no necessity for the power distribution board really so you could save yourself even more money - just parallel off the two speed controllers to the one battery and instantly reduce the weight if that's your choice
The reduction in run time means changing the battery more often though













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Roadrunner

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Re: What Motors,
« Reply #10 on: February 28, 2011, 04:04:48 pm »

I'm not slating the use or users of Lipos in the right circumstances they are the best to use, but in this situation i believe it to not to be in the users best interest to get involved, i have over the years tangled with Lipos in Electric cars, and found it nothing but an expense, with little improvement over the use of higher rated NicD's which are far safer to use and less expensive.

If I really was going to suggest an upgrade to the OP's boat then I would also have suggested going for a decent pair of brushless motors too.

You basically did, Lipos then Brushless motors..... next it will be surface drive .....

In this instance wullie/mk2 is clearly not prepared to pay out much to improve the performance of such a large model, lipos are just an expense that need not be spent for not much in the way of improvement, some models have a 'peek' performance as it is, and you have to consider that the models output could be that of a 'scale' like speed, which in all honesty should be good enough.

But as i suggested try the little things, change in prop's, weight reduction in the way current power is provided and see if that makes a difference, its all far to easy to get carried away with suggesting 'the best tech' but not everyone can afford it, and not everyone needs it!
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malcolmfrary

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Re: What Motors,
« Reply #11 on: February 28, 2011, 04:20:15 pm »

Provided that one battery would handle two motors, just removing one battery will increase performance by reducing weight.  At the same time, the duration might well not go down as far as the plain maths would suggest, again, due to having less to shove around.  This assumes that the boat can stand sitting higher in the water.
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Roadrunner

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Re: What Motors,
« Reply #12 on: February 28, 2011, 04:27:39 pm »

I have no doubts a 12v 7ah LA will run both 800 sized motors , run time will be far reduced since there are no longer 2 in parallel, by how much your right it will be unknown until its tried, i have a feeling that the boat was/is sat to heavy in the beginning given that a 12v 7ah is around the 2kg mark so 4kg + the boat + any other ballast used to trim it out. If it is to high you still have the option to add more ballast weight but it may be far less then a 2nd LA battery.

There is also the options with mixers to aid in turning should it lean to far during a turn with the decressed weight, addressing these things first i feel is the best way forwards before getting into other more expensive options.

Mixers, prop size/ shape/ style, weight reduction, trimming ballast...
 
As i said all subject to trial and error.
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Shipmate60

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Re: What Motors,
« Reply #13 on: February 28, 2011, 06:23:47 pm »

The recommended motors for this model are MFA 850's.
These spin at about double the speed of the 800's (9000+ and 5000+ rpm), but will have a higher current consumption, roughly 11 amps running.

Bob
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Roadrunner

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Re: What Motors,
« Reply #14 on: February 28, 2011, 06:35:26 pm »

''semi-scale radio control model of the Fairey Marine Tracker coastguard patrol boat
Seven pre-coloured Glassfibre mouldings for hull, deck, superstructure and fittings
Suitable for twin Torpedo 800/850 or equivalent motors, The Tracker has a unique moulded motor, battery and shaft 'tray' for easy motor mounting and shaft alignment.''

Either works fine... and im sure its been previously stated that he is unsure if he wants to buy new 850's....

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Shipmate60

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Re: What Motors,
« Reply #15 on: February 28, 2011, 08:43:26 pm »

The 850's are then equivalent to the original Marlins and give a good idea about shaft revs.

Bob
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wullie/mk2

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Re: What Motors,
« Reply #16 on: March 03, 2011, 12:45:15 pm »

Thanks for all the suggestions,..and especially to Roadrunner,..I,ve opted for the Action P102,i will let you know how i get on
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Roadrunner

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Re: What Motors,
« Reply #17 on: March 03, 2011, 02:43:16 pm »

 :-)) no worries mate, let us know how it goes.
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