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[tizdaz]

Hi guys,


Would this motor be a good choice for a 1/12 scale tug running on 24volt?
http://vi.raptor.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=192010175441&category=47349&pm=1&ds=0&t=1478963955346

Heres more specs of the motor:
http://gindunmotor.com/Showpic_en.asp?ArticleID=207

Cheers

[Netleyned]

What Motor???

Sorry, just found it

Ned

[tizdaz]

No prob my bad, i forgot to add the link! But fixed it now, in the 2nd link its the last motor in the list (24v 150w)

[Allnightin]

At the price being asked I would say it is worth trying.   I rewound two shower pump motors to achieve similar specs and they propelled a 1/32nd Type 42 destroyer displacing about 300 lbs via about 2:1 reduction to 6" diameter 5 bladed props. The model did about 8 feet per second at full power.

[tizdaz]

Aye, the other motor i was looking at has VERY similar specs including voltage/dimensions etc, except it costs £80 from a model shop! Although one at model shop states it has 12 poles so not sure how many this one has? Also not sure what 150watt means?

[Allnightin]

Also not sure what 150watt means?

Quite a lot of power and enough to move quite a large displacement hull in model boat terms at a respectable speed as per my earlier message!

[tizdaz]

Oki doke!


Thanks allnightin, think im going to order one and give it a try

[tizdaz]

Also, if i decided to run a 24volt motor on 12 volts, is this ideal? What are the positives and negatives (if any?) running a setup this way?


Thanks again!

[Allnightin]

You will get one quarter the power you would with 24V

[tizdaz]

Ah oki doke, i also had a browse on net, alot of comments i read was a 24v motor running off a 12v supply is much less efficient (by around 40%!) to that of a 24v motor running off a 24v supply and if a choice is available use 24v motor with 24v supply?

[jarvo]

Hi Tizdaz, had a look at their ebay site, for the price and performance go for it. If they can handle an electric bike the torque to turn a big prop will be no problem, also gives you a good run time with decent AH batteries, my Amsterdam runs for about 2 hours at  silly speed, it has 2x 10ah gel cells, handy because they form most of the ballast!!!! HEAVY


Regards


Mark

[tizdaz]

Hiya Mark


Yeh im going to get one and give it a go for.the price, like you say, the batterys will help ALOT with the ballast!


Amsterdam tug! That was my 1st (and only!) rc boat i built many years ago, but i never got around to completing it :-( but was a lovely kit


So this build is going be huge for me, looking forward to it alot


Hey i just noticed your from stockport, not too far from myself (chester) will have to meetup sometime! Do you goto any of the rc boat meets? Im defo going to be going some next year

[Stavros]

Sorry not enough rpm in that motor with that hull
.....your money your choice.... BUT as I previously said to you.
...as i KNOW FROM EXPERIANCE as i have one.....you NEED 4K RPM on this hull.




Dave

[tizdaz]

Hiya Dave


This motor is almost 3600rpm so its just short of 4000 so thought it would do the job, you think it not be suitable because if not then i dont know where to find a suitable motor thats 24volt as the one i was going to get from model shop is pretty much exact same spec :-( ?

[Stavros]

Brushless 420kva on 12v wil give you 5k rpm more than plenty....all you got to remember is one little thing......you dont drive a ferrari flat out everywhere do you.....never fit a motor in a model that will just do the job..allways have something in reserve.




Ive got a 6 foot happy hunter tug powered by a 750kva motor swinging a 4 ins 4 bladed prop,that weighs in at 150lbs on the water....It is sailed on half throttle....but has masses of reserve power.




Allways consider you need more power than what you think




Dave

[Allnightin]

Can you give the specs of the prop - diameter and pitch - and some idea of hull size please?

The example I gave with my Type 42 had the shafts turning at around 1500 rpm and the props had about 7" pitch for about 5 mph top speed.  Obviously the hull form is much finer on the T42 so there would be a lot less prop slip than for a tug but at 150W levels of power you should still be able to get a decent speed providing you can match the motor output to the prop - although you may need to gear the motor output up.

I haven't used brushless so can't answer for them but if they avoid gearing to match the prop to the motor then that could be an important factor in what is best for your model.

[tizdaz]

Ah i see what you mean, i will have a think and see if i can find a similar motor with more rpm, if not for the sake of £20 i will give this motor a shot, if it isnt ideal i will store it abd use it on my next build that will be a smaller scale, less weight etc

[tizdaz]

Can you give the specs of the prop - diameter and pitch - and some idea of hull size please?

The example I gave with my Type 42 had the shafts turning at around 1500 rpm and the props had about 7" pitch for about 5 mph top speed.  Obviously the hull form is much finer on the T42 so there would be a lot less prop slip than for a tug but at 150W levels of power you should still be able to get a decent speed providing you can match the motor output to the prop - although you may need to gear the motor output up.

I haven't used brushless so can't answer for them but if they avoid gearing to match the prop to the motor then that could be an important factor in what is best for your model.

Hiya


Sure no probs, its 6" prop with a 7.0" pitch, 4 blade, its from.prop-shop under standard props section on second page

But i was also thinking about the 5.1" prop with 6.0" pitch?


The hull has an 18" beam and is 71" in length

[Allnightin]

Thanks - the T42 props were from Prop Shop and 5" diameter with 6" pitch when I checked my notes.

A 6ft hull is not going to go much faster than about 3.8 mph (Froudes Law) which is about 5.5 feet per second if I have my calculations right

Allowing for 60% slip as per Prop shop info for heavy towing would suggest about 1400 rpm shaft speed.

That size prop will need gearing down by at least 2:1 from motor speed so the 2800 rpm max efficiency speed stated might work out OK but that means a 9+ Amp current draw

If you are able and willing to make up a reduction belt rig and do a bit of trial and error experimenting to get the best gear ratio then I think this can work with this sort of cheap motor but if you haven't done that before then maybe use something that will drive the prop directly.

[tizdaz]

Hiya Allnightin, thanks for that info

This is getting pretty confusing lol :-(


The original motor i was going to buy was a 12 pole 24 volt motor and had a max rpm of 4000, i spoke to the guys at shop and explained to them my needs and the size/weight of my tug and prop etc, and they said it should be fine, this cheaper motor looks to be pretty much exact same spec except i dont know how many poles it has, do the amoumt.of poles make a big difference or?


I would happily get the more expensive motor but like i say it seems the same spec as cheaper one. So am i being told porkys at the model shop just for a sale maybe? Ive heard lots of good stuff about them but it not nice if they tryin to fib me!


Think for now i will jist try the cheaper motor, at least then if it is an epic fail then ive only lost out £20 instead of £80+, as they are both same spec


Cheers

[Allnightin]

I paid more than that for the motors I used about 18 years ago so these are very cheap and the original motor you were considering could well be more expensive as that was the normal going rate.

As I understand it, the more poles there are, the greater the torque available but the slower the max speed.  You could ask Electro scooter how many poles using the phone number they give.   If you are going to use one then you could also ask about drive belts and gear heels for the reduction arrangements you will also need at the same time.

[jarvo]

HI Tizdaz, dont think the model shop is conning you but remember buying from a wholesaler is always cheaper than a shop which only sells 1 or 2, I would go with the scooter motor and ask them how many poles it has, scooter and kids car motors are quite powerful even with them geared.


Mark

[Stavros]

just out of interest which model shop did you ask about a motor




Dave

[tizdaz]

Hiya guys :)


@Stavros I don't want to name the model shop as in all fairness they have been helpful with other things i've asked bout & I will be buying other bits n bobs from them during my build probably, last thing i want to do is the so called "name & shame" when really at the moment they haven't done anything wrong & have been helpful, i was just curious as to why they say the motor they sell (which looks to be exact same as the one on fleabay) would be ideal for my tug but I've heard otherwise in some of the reply's, i'm just a little confused i guess at the mo lol :)


I will ask how many poles the ebay motor has & take it from there, but like i say for the sake of £20 ..i will prob pick one up & give it ago, in the worse scenario if it isn't upto the job, i can use it in another smaller model i might decide to build at a later date :)


Im guessing by now some of you might have noticed how particular i am with things! ..i like to plan ahead so things can go smoothly as possible, i know during my build things will crop up with a response such as "WTF!" but as im a complete newbie to scratch builds & one of this size i want to get as much planning done as possible to give me a head start! ...so a big THANKS to all of you so far that have put up with my "noob" questions, i have also joined another forum and asked similar questions to which i did get a response from one of its "old time" members basically saying i know nothing & stop asking stupid questions!! ..but on the whole the rest of the replys have been helpful :)


So cheers again guys... you want to know the scary thing? ...i havent even started my build yet... you guys wont know whats hit you when i do start haha!! (jus kidding!) :) :)

[tizdaz]

Well, this has put a spanner in the works.. Just got a reply from prop-shop..


"for this large tug application I would recommend the larger prop, part number std 6070/4. The type of motor to look for is a heavy duty, medium rpm traction motor such as used in electric wheelchairs, car seat adjusters or car fan motors. The output needs to be about 500 to 700 watts with a speed range of 1000 to 3000 rpm .  Often such motors can be found online or with surplus/scrap dealers"

500-700watt with an rpm of 1-3000 and draws 27amps!? Smallest motor i could find with this kind of spec was 30cm long, surely i dont need that amount of power?