Model Boat Mayhem

Technical, Techniques, Hints, and Tips => BRUSHLESS Motors and Speed Controllers => Topic started by: knoby on November 26, 2009, 10:35:57 PM

Title: sugestions for brushless 1/24th swordsman
Post by: knoby on November 26, 2009, 10:35:57 PM
Hi all,

I have just acquired a hull for a 1/24th scale (17 inch) swordsman & thought it would be a good opportunity for a cheap first venture into brushless motors. The recommended motor is a 400 size & after a few evenings going through the various sites i am none the wiser as to which motor/esc to use.

I want fwd & rev & don't really want to use lipo batts as i have 3 sets of 7.2 volt 3000man nimh cells.

any help or suggestions would be greatfully appreciated, but please don't get too deep.

Many thanks Glenn
Title: Re: sugestions for brushless 1/24th swordsman
Post by: HS93 (RIP) on November 27, 2009, 02:24:20 AM
I did a small deans fire boat and made it twin shaft I fitted two Mystery D2836-1700 motors and two Turborix reversing speed controllers, it was totally over powered and I like fast, I am now putting them in a bigger boat and going 380s. but One would be ideal they had good run time of a 7.2v 5000 battery two motors of one battery the main reason for the Chang is that the weight of twin speed ctr  and they where difficult to get in sync a few people off the forum saw it at the deans show and there is a video of it
one would be ideal for the swordsman it would make it plane and the run time would be good they are also very cheap, I went for the turborix speed controller that is a bit higher in amps as i thought for the few extra pounds if the motors where to small I could go bigger but they are now very cheap , I started the project about 3 tears ago in fact there is a build blog on the fire boat web site, so there was not the information that there is now and prices have drooped. hope this helps  ps boat was not finished in pictures controllers not mounted and it needed finishing off. I got my speed ctr from R2 hobbies but could not remember where the motor came from
Title: Re: sugestions for brushless 1/24th swordsman
Post by: FullLeatherJacket on November 27, 2009, 08:22:52 AM
Much as it grieves me to mention "The Enemy" (only joking, Steve), I think you'll find MTroniks do a combo of a 400-equivalent brushless motor and a Forward/Reverse ESC for about fifty quid. Probably made in ROC but at least you can get UK techinical support if things go a bit pear-shaped.
My own 20" Swordsman is mainly balsa and goes very well on a Speed 400 with a 6 x AA NiMH pack. 25mm dia PropShop 2-blade brass prop used.
Title: Re: sugestions for brushless 1/24th swordsman
Post by: nick_75au on November 28, 2009, 01:01:28 AM
A 22 mm diameter 22- 20  can not bell style diameter out-runner in the 1000-1200 kv range and a 30 -35 mm prop will do the job

35 amp more than enough or the M-tronics brushless boat esc

Title: Re: sugestions for brushless 1/24th swordsman
Post by: knoby on November 28, 2009, 09:11:41 AM
Brilliant, thank you guys, especially for the links, it makes it so much easier.

cheers glenn
Title: Re: sugestions for brushless 1/24th swordsman
Post by: knoby on June 02, 2010, 09:05:07 PM
Thought it about time i updated the thread. The first attempt at powering the boat didn't go well, mainly due to me not really listening to the advice given on here.

I was fortunale to find a second hand turnigy 35 amp marine esc that someone had bought but never used. I used a small 2100kva outrunner the I was given by a friend. It was originally for a 'foamie' aircraft & was very small. It seemed to lack the torque required to drive the boat at a reasonable speed.

I changed it for the motor HS93 recommended, but this time the boat would get on the plane & then the esc would cut out. presumably because the bec circuit was lacking volts. Further investigation showed that the old ni cads i was using were past their best & although they would seem to charge OK, as soon as they were put on load they dropped voltage quickly. 

A new pack of 6 4500mah ni mh were installed, & the boat tried again. WOW what a difference !!! It hurtled across the lake much faster than i had expected. The shaft is a m2 thread, which limits the props easily available. This first run was made using a Graupner 30mm 3 blade prop which has a very low pitch, but still gave a very good turn of speed. The only other prop i had was a 24mm very coarse pitch, runs with this prop were exciting, but not without problems.

with the 24 mm prop the boat 'blew away club 500 racer in a straight line, but the boat sat at an angle due to the torque reaction & would have turned over if i had applied full rudder to starboard. Also it porpoised when running flat out. Run times were surprisingly long, around 25 Min's flat out, with the motor & esc only getting slightly warm

I think the prop answer is somewhere in the middle of these 2 sizes, I'm thinking propshop 3 blade 30 mm should do the trick.

Many thanks to all who suggested motors etc, i really didn't know where to start with this one.

I had better get the model finished now !!

Cheers Glenn.

Title: Re: sugestions for brushless 1/24th swordsman
Post by: HS93 (RIP) on June 02, 2010, 09:51:59 PM
Hi glad it worked , my fire boat was like a rocket ship with two in far to fast  so out they came.
you could try getting an adapter made I got a shaft from ASTEC 2mm with a 4mm end if you know someone handy local with a lath they could do one in 5 min or ask Prop shop I think he did them, I used two 25mm 3 bladed props from prop shop but never really tested it for long enough because it would lay on its decks in turns.

it wasn't a set of old car nicads was it ? I tried a set of my old ones not long ago and they where the same Cr*p..

have you thought of a nice light weight lipo that motor will run 12v..for calm days.

Title: Re: sugestions for brushless 1/24th swordsman
Post by: knoby on June 02, 2010, 10:10:04 PM
Hi Peter, Actually the old cells were scrc 2000 from my old formula 1 eco boat, there were about 10 years old 7 hadn't been used for years. They were stored discharged 7 i cycled them 6 or 7 times before trying them. The individual cell voltages seemed OK, as did the overall voltage, but they just didn't perform.

I don't have a selection of m4 props either, so i am going to have to buy some no matter what size. To be honest I was happy with the performance on the 30 mm 3 blade prop, the 24 mm prop is too much although lots of fun.

most surprising for me was the running time, even on the fastest prop the motor & esc temperature was bearly warm, & gave in excess of 20 mins run.

Cheers Glenn