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Author Topic: Milford Star, what engine should I use?  (Read 7728 times)

David Boreham

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Milford Star, what engine should I use?
« on: September 23, 2019, 06:28:22 pm »

i am sorry if  it is becoming boring all the questions about the Milford Star!  What engine would you use, believe it or not but Caldercraft don’t mention what engine to use in the instructions. On the plans they mention a mono perm or similar s/n! I am busy trawling the internet and web sites that sell the kit to see if there are any recommendations there!  If anybody knows a blog with photographs as a guide to build, please add a link, I think I am going to need it!
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Shipmate60

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Re: Milford Star, what engine should I use?
« Reply #1 on: September 23, 2019, 06:50:16 pm »

A monoperm is a 380 sized motor that runs on about 5000 rpm on 6 volts.


Bob
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DaveM

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Re: Milford Star, what engine should I use?
« Reply #2 on: September 23, 2019, 06:54:18 pm »

This one will do you nicely on either 6v or 7.2v. https://www.componentshop.co.uk/385-dc-motor-mounting-bracket.html
DaveM
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David Boreham

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Re: Milford Star, what engine should I use?
« Reply #3 on: September 23, 2019, 07:02:57 pm »

Thanks, I have just seen on Cornwall model boats site another engine but was waiting for your responses.  They recommend or should I say people who bought the kit also bought MFA RE-540 1 3 pole Dc Motor Inc mount< only £8.93.  What do you think, I will also need to buy a battery and electronic speed controller.  Any recommendations really appreciated.
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Capt Podge

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Re: Milford Star, what engine should I use?
« Reply #4 on: September 23, 2019, 07:49:25 pm »

I've used the 540 in 8 of my models and not had a problem with any of them so far. I use mtronics viper marine ESCs (either 15 or 20amp)and usually 6 or 12v sla batteries, although 2 of the models have 3300 nmh batteries for the speed increase. When I get around to building my M.Star the 540 will be my choice. I think it will be a little overpowered but that comes in handy to get out of the way of models whose owners aren't paying attention.


Regards,
Ray.
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David Boreham

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Re: Milford Star, what engine should I use?
« Reply #5 on: September 23, 2019, 07:54:19 pm »

Ray,


I was thinking along the same lines, the additional power will be useful as I will be sailing at my local yacht club, which is quite exposed and going against the wind may well need that additional umpf!
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Colin Bishop

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Re: Milford Star, what engine should I use?
« Reply #6 on: September 23, 2019, 08:08:19 pm »

Read up on the 540 motors. The specifications can differ hugely. You would probably be better off with a 5 pole low drain motor.
Colin
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malcolmfrary

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Re: Milford Star, what engine should I use?
« Reply #7 on: September 24, 2019, 09:15:07 am »

Read up on the 540 motors. The specifications can differ hugely. You would probably be better off with a 5 pole low drain motor.
Colin

540 motors do have a huge range of variations, usually for faster and even faster applications.  The one mentioned here was a 540/1, the /1 being very important.  It indicates that the motor is wound differently to give torque at modest current rather than high revs at high current.

In past times, a 545* would have been a preferred choice, but these seem to be rare, the 540/1 has been recommended as a suitable replacement for the 5 pole motor.

Regarding monoperms, they came in a variey of forms as well. 
There is a table showing them at:

https://www.modelboatmayhem.co.uk/forum/index.php/topic,11713.msg411055.html#msg411055

*NOTE:  A 555, a totally different thing, mostly good as a paperweight as far as most boat modellers are concerned.
 
 
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Subculture

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Re: Milford Star, what engine should I use?
« Reply #8 on: September 24, 2019, 11:39:07 am »

389/385 sound a bit small to me for a model of around 3ft unless some form of gear reduction is used to amplify torque. What's the diameter and pitch of propeller on that model. The 540 motor sounds a better bet.
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canabus

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Re: Milford Star, what engine should I use?
« Reply #9 on: September 24, 2019, 12:42:40 pm »

Hi DB
The 540 rock crawler 80 turn motor is rated at 5500 rpm@ 7.2 volts and will easily turn up to a 3 blade 60mm prop.
Canabus
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DaveM

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Re: Milford Star, what engine should I use?
« Reply #10 on: September 24, 2019, 01:26:05 pm »

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Buccaneer

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Re: Milford Star, what engine should I use?
« Reply #11 on: September 24, 2019, 02:24:43 pm »

Nothing wrong with a 555. I have them fitted in my Mountfleet Puffer, Sterling American Scout and Mountfleet Osprey.

John
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malcolmfrary

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Re: Milford Star, what engine should I use?
« Reply #12 on: September 24, 2019, 04:01:14 pm »

Nothing wrong with a 555. I have them fitted in my Mountfleet Puffer, Sterling American Scout and Mountfleet Osprey.

John
Of course, I might have been thinking of the infamous 550 which was very much on offer on fleabay for a long time. :embarrassed:
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DaveM

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Re: Milford Star, what engine should I use?
« Reply #13 on: September 24, 2019, 04:49:25 pm »

Malcom
You probably are. A Mabuchi 555 is a very nice motor for displacement vessels when run at 12v (approx 5500RPM and single amps). I think this is the one you remembered:
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Colin Bishop

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Re: Milford Star, what engine should I use?
« Reply #14 on: September 24, 2019, 05:58:20 pm »

Dave,

A couple of those fitted to a wheelie bin would make it live up to its name.  :o

Plenty of room for the necessary LiPos inside too.

Colin
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DaveM

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Re: Milford Star, what engine should I use?
« Reply #15 on: September 24, 2019, 07:38:37 pm »

Dave,

A couple of those fitted to a wheelie bin would make it live up to its name.  :o

Plenty of room for the necessary LiPos inside too.

Colin
Nah - it'd melt a wheelie bin!  8)
DM
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David Boreham

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Re: Milford Star, what engine should I use?
« Reply #16 on: September 25, 2019, 07:25:19 am »

Damn, I am more confused than ever, I thought I had made a decision and was destined for a 540 but now not so sure!  I had hoped to start building on my next three days off from work, in which time Engine, battery and esc would have been bought and if not delivered, on their way.
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chas

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Re: Milford Star, what engine should I use?
« Reply #17 on: September 25, 2019, 08:47:06 am »

I understand your confusion, the whole motor labeling subject can be very confusing.
   Based on the replies and my own experience, you were considering a 540 / 1 from the excellent Cornwall model boats, just get that one. As Malcolm said, it's a good torquey motor, great on 6 volts. I have used them and I'm very happy with the results. I agree there are other good options, but why get bogged down when you'd rather be building.


  Chas

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grendel

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Re: Milford Star, what engine should I use?
« Reply #18 on: September 25, 2019, 02:16:53 pm »

in my 40" model 10" wide I started out with a 385 geared motor on 12V, that was too slow so I moved to the 385 without gears, that got hot on a 30mm prop, so i moved to a 540 motor, that works fine without getting hot on a 35mm prop (all the motors are the MFA ones) the 540 draws about 1.2 amps at no load (ie prop out of the water)
the 540 may be a bit on the overkill side, but gives me an extra nudge of power to get out of trouble.
https://www.mfacomodrills.com/pdfs/RE540-1.pdf
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cdnfurball

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Re: Milford Star, what engine should I use?
« Reply #19 on: September 29, 2019, 03:19:37 am »

I am currently working on an old time fishing trawler. I have also gone through the same problem....    Motors, prop size etc.   I settled on a 540 motor with 80 turns, the prop is 3 bladed, 40 mm diameter with 7.2 volt battery.  Because it is not a go fast boat, l went with a brushed motor.
The brushed motors are less money than brushless, BUT don't go cheap !       You get what you pay for.....  Pride in your build is gone when it's powerless and drifting


I bought 3 of the 540's but each has different turn ratings ( l figured one would do the job ) the other 2 motors....    possibly future projects.





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David Boreham

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Re: Milford Star, what engine should I use?
« Reply #20 on: October 04, 2019, 12:38:59 pm »

Well I bought a 540/1 which was recommended by Howes models and Cornwall Model Boats which were very helpful. I am using a 6v battery. Speaking to my Father an 88 year old retired now model boat builder, he is suggesting I drill the prop shaft tube to weld a branch to it so that I can top up silica grease as the prob shaft may run hot.  Any thoughts, I think my Dad is pushing my engineering/modelling skills to the extreme!
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Capt Podge

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Re: Milford Star, what engine should I use?
« Reply #21 on: October 04, 2019, 01:48:02 pm »

Your father's advice is sound David. I think you would struggle to get the propshaft out for maintenance, the only way to do so would be to a. Remove the propeller, b. Remove the coupling and motor and, c. Pull the propshaft into the hull (IF there is sufficient access and clearance to do so).
You could of course uncouple the rudder shaft and bend the skeg to remove the rudder then you undo propshaft coupling and pull shaft out that way.

Caution : bending and straightening the skeg will weaken and ultimately snap it!

Best listen to your Father...


If your soldering/brazing skills aren't up to it, there are kits out there that attach oiling/greasing tubes directly to the prop tube - I'll see if I can find a link...


Regards,
Ray.
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Capt Podge

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Re: Milford Star, what engine should I use?
« Reply #22 on: October 04, 2019, 02:04:17 pm »

Here's one link - there will be others available :-
https://www.modelboatbits.com/MobileDetail.php?Prod_ID=4601

Regards,
Ray.
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David Boreham

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Re: Milford Star, what engine should I use?
« Reply #23 on: October 04, 2019, 04:00:21 pm »

Ray,


Thank you, I will give it a go.  You have to learn sometime.  I just looked at the link though at that is a good clean way of doing it.
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Dave_S.

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Re: Milford Star, what engine should I use?
« Reply #24 on: October 04, 2019, 06:06:23 pm »

You're certainly making better progress than I am, my Milford Star is still in its box in the loft!
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