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[frogman3]

Hi Chris, No I'm not saying that and I'm sorry if this is preaching but the angle that the blade cuts into the water has an effect on the push that the prop gives. So a shallow cut would normally be combined with a faster revving motor and a steep angle would combine with a slower revving motor. So a 45mm prop would have anything from a 40mm pitch to a 60 or 70mm pitch where the low pitch angle would suit a faster and the high angle would suit something like a steam engine. One of the main factors is the torque produced by the motor so if you have a fairly high torque motor like the 555 it will take a prop with a higher pitch angle while a standard 540 won't, even though the power could be the same. So check the torque rating for the motors you've got and see where they lie. The "C" type Raboesch props in Rob's earlier post have a shallower angle than the "A" type in his later one but even those could be a bit steeper, the normal scale type Prop-Shop ones being steeper still. Not a lot but. as I said, it could be worth talking with them.
Tony

AN HI Tony well to cut a long story short to me if ive got this right is the more the angle of the  prop blades bend towards the prop boss the more the prop thrust will be yes ? an it then needs a high touge but low power motor like what martin reccomened as i have bought them big motors yes ?
chrisb

[tonyH]

Yup! The right prop will make the best use of the torque and power you've got going for you. Speak to prop-shop!

[HMS Invisible]

HI ALL you guys who said that the 555 motors would best well they are what i asked for at w/w an the chap said no they be to low a power an sold me them 540 motors which are badly underpowered so ive found on her last sail she was hardle movin so ive gone on what martin recomended an will try them thanks for all your advise guys
chrisb

My caveat along with "In my opinion the 555 is the optimum choice." included:-
 "I think I saw a photo of coarse pitched scale brass props" and "On 12v the 555 would measure in the region"

All those guys were right but so was Iain at Component Shop if its taken into consideration.We both would have learned DC Motor theory in first year doing electrical engineering and the fundamentals don't leave you after decades.

 The motor with the higher rpm on the data sheet will initially be higher power. You need a prop that will give thrust whereupon the 555 outputs more power at its peak and there is still headroom above 12volts before it reaches its own thermal limit due to losses.
 It's probably a good thing that you went for a much higher power motor because I've experienced the wind effect when trying someones eleven foot King George V battleship. It was like a giant scary yacht at the mercy of the elements while you slam four decaperms and props from full ahead to reverse power as you change the angle to battle the wind.

[frogman3]

to HMS Invisible so to keep this simple are you sayin that ian from
compornets shop did right by steerin me away from the 555 an puttin me onto the MFA 540 MOTORS ?
An yes i know i need bigger props as cant go any bigger than 45mm diamitter or the props will hit the hull
chrisb

[HMS Invisible]

to HMS Invisible so to keep this simple are you sayin that ian from
compornets shop did right by steerin me away from the 555 an puttin me onto the MFA 540 MOTORS ?
An yes i know i need bigger props as cant go any bigger than 45mm diamitter or the props will hit the hull
chrisb

For the props you originally had the 540 was right and so might the speed 600 for that matter.
As you go to more blades,  coarser pitch and bigger diameter the 540 can't run efficiently, would be SLOWER so therefore less mechanical power output and drawing more input electrical power than the correctly matched motor. So the next in line is the 540LN then 555 and onto a bigger size of motor as the prop thrust increases.
If you are talking the coarse pitch 45mm 5 blader the 555 motor and upwards will cope. I wholesaled 555s by the hundred box to some of the traders and kit makers for 3 inch multi blade props that prop shop would cast.
The anecdotal replies from others about 555s directly driving big props are no surprise to me.

A cheap infra red tacho and motor data sheet tells you that at a glance and you don't have to break open the circuit for current measurement or use wattmeters that electric flight users would do. Component shop is electrical rc gadget oriented so maybe sells them. I got one from Ebay.
.....
I could add when you overprop a motor you can install reduction gearing to the same motor as an alternative to fitting a 540LN or 555 or larger on direct drive. The drive shaft turns faster if you had it overpropped on direct (1:1) ratio.

[frogman3]

For the props you originally had the 540 was right and so might the speed 600 for that matter.
As you go to more blades,  coarser pitch and bigger diameter the 540 can't run efficiently, would be SLOWER so therefore less mechanical power output and drawing more input electrical power than the correctly matched motor. So the next in line is the 540LN then 555 and onto a bigger size of motor as the prop thrust increases.
If you are talking the coarse pitch 45mm 5 blader the 555 motor and upwards will cope. I wholesaled 555s by the hundred box to some of the traders and kit makers for 3 inch multi blade props that prop shop would cast.
The anecdotal replies from others about 555s directly driving big props are no surprise to me.

A cheap infra red tacho and motor data sheet tells you that at a glance and you don't have to break open the circuit for current measurement or use wattmeters that electric flight users would do. Component shop is electrical rc gadget oriented so maybe sells them. I got one from Ebay.
.....
I could add when you overprop a motor you can install reduction gearing to the same motor as an alternative to fitting a 540LN or 555 or larger on direct drive. The drive shaft turns faster if you had it overpropped on direct (1:1) ratio.

HI HMS INVISABLE
A FREIND has shown me this site for props


try here.



148 - 5 blade METRIC - Raboesch Models

raboeschmodels.com45mm brass 46.1 pitch. only 4mm shaft though. About £21 each.

an this prop above may be the ones i need 45 mm diamitter  46.1 pitch an 4 mm shafts so im goin to try an get these from cornwall model boats if poss
chrisb

[Rob47]

Chris
With what you describe I think I may have part of the answer.  You say she was moving slowly and although rudder hard over turning circle was huge,  this I believe is the same as large 1/1 vessels have, lack of steerage way i.e. they are not travelling fast enough for the flow of water over the rudder to have any effect, hence you see tugs assisting at slow speeds.


Bob

[HMS Invisible]

Chris
With what you describe I think I may have part of the answer.  You say she was moving slowly and although rudder hard over turning circle was huge,  this I believe is the same as large 1/1 vessels have, lack of steerage way i.e. they are not travelling fast enough for the flow of water over the rudder to have any effect, hence you see tugs assisting at slow speeds.


Bob

Indeed.
Look at the control surfaces relative to the prop on a fast attack sub. 
Los Angeles Class (ssn)
Your post has reminded me of the mention of pumps used as stern thrusters in the sub model build threads.

[frogman3]

Chris
With what you describe I think I may have part of the answer.  You say she was moving slowly and although rudder hard over turning circle was huge,  this I believe is the same as large 1/1 vessels have, lack of steerage way i.e. they are not travelling fast enough for the flow of water over the rudder to have any effect, hence you see tugs assisting at slow speeds.


Bob

HI Bob an hms invisable
yes i realise now the prob an have done all last two wks or so as thats the reason ive treid cornwall model boats to try an order 45 mm bigger props but we have phoned them 3 times an all we get is leave your phone no. which jen did but no reply an ive sent them an email an no answer as they are busy so will have to try an find some other prop maker as ive also looked at prop shop but cant really understand the website an find the props i want so till i do im stuck
chrisb

[Akira]

Chris, Try George Sitek. His props are right up there with the Prop Shop. Beautiful stuff. I have them on my Fletcher as well as my Juneau.http://gsitek-props.co.uk/

[frogman3]

Chris, Try George Sitek. His props are right up there with the Prop Shop. Beautiful stuff. I have them on my Fletcher as well as my Juneau.http://gsitek-props.co.uk/

HI Akira
well ive looked at mr Sitek's site an found the 5 bladed props
an not really happy as it dont say the pitch of the blades as i need 45mm dimater an pitch 46.1 an 4 mm thread but from what i see the props are just the normal petal props but i was hopein for some in my linkpic below
https://ibb.co/nrhqbzB
chrisb

[Rob47]

Chris not sure why you having problems, but 5 bladed are clearly shown.  Click on products, Type M props and there you are.


he is not the most reliable now sadly though


Bob

[frogman3]

Chris not sure why you having problems, but 5 bladed are clearly shown.  Click on products, Type M props and there you are.


he is not the most reliable now sadly though


Bob

HI Bob well who would you reccomend ?
chrisb

[Rob47]

Cornwall models, I know you have had problems but that's my choice, never has issues with them but as you say might be busy time.


Bob

[frogman3]

Cornwall models, I know you have had problems but that's my choice, never has issues with them but as you say might be busy time.


Bob

YES you maybe right Bob but when will they be unbusy ? so i can get an answer off them ? an you say sitek is not very reliabele so that cut down the odds of me gettin my props an i find prop shop site is complex anyone else know where i can get my props made ?
chrisb

[Martin (Admin)]

Cornwall models, I know you have had problems but that's my choice, never has issues with them but as you say might be busy time.

Bob

https://www.cornwallmodelboats.co.uk/acatalog/m2-raboesch.html

[frogman3]

https://www.cornwallmodelboats.co.uk/acatalog/m2-raboesch.html



HI Martin many thanks for the info but ive just found out this morning that i think i may have to fit 55mm bladed props as it been well over ten try since i bought any props an i have forgottern what type of props i need to push  this very heavy model along so i contacted a boaty m8 who bought my HMS EDINBURGH an its a big model an i asked him what size props i fitted on edinborough an he say 55mm diamitter an she sailed lovely so no 45 mm now so that means i will have to drill out all 4 props shafts an clean them up an refit them back in the stern section so at least another 6 months work there so she wont sail anymore till 2024 oh dear 
but no good buyin a lot of moneies worth of props if they are still not big enough
chrisb

[Martin (Admin)]

https://www.cornwallmodelboats.co.uk/acatalog/m2-raboesch.html

HI Martin many thanks for the info but ive just found out this morning that i think i may have to fit 55mm bladed props as it been well over ten try since i bought any props an i have forgottern what type of props i need to push  this very heavy model along so i contacted a boaty m8 who bought my HMS EDINBURGH an its a big model an i asked him what size props i fitted on edinborough an he say 55mm diamitter an she sailed lovely so no 45 mm now so that means i will have to drill out all 4 props shafts an clean them up an refit them back in the stern section so at least another 6 months work there so she wont sail anymore till 2024 oh dear 
but no good buyin a lot of moneies worth of props if they are still not big enough
chrisb


 

[Rob47]

Chris why do you need to drill the prop shirts out to change props assuming you are sticking to M4
Bob

[frogman3]

Chris why do you need to drill the prop shirts out to change props assuming you are sticking to M4
Bob

HI Bob well i need to drill all 4 prop shafts out an reset them as  because the bigger props will hit the hull as im goin to fitt 55mm props now an not 45mm as i was intending so it gonns be a lot of work providein i can do it that is as the hull curves in where the prop shafts are so not good but got to be done but will be done over nxt yr
chrisb

[ballastanksian]

I hope the refit goes well matey. You'll get there.

[frogman3]

I hope the refit goes well matey. You'll get there.

I Certaintly hope so but mojo is low at the moment an when i am able to get some props gonna phone cornwall m/b tomorrow for 4 th time
cheers sir

[frogman3]

Hi Chris,




As Rob said, I would not add additional rudders just yet, I’d first change the motors and test them with the Five bladed props.


I’m surprised you were told the 555 motors were not suitable, USS Roosevelt is running on these motor and 50mm five bladed props and as you know she runs at a good scale speed.

HI Dave yes i was surprised that ian from components shop said the treble 555  motors  were not the ones i needed but thats what he said an reccommed the mfa 540 motors which are not what i needed an yes your props look great an they are the sort that i want but im goin for 55 mm dia an what pitch are your props an are they 4mm thread an were did you buy them from ? please as i will try there
ATB
chrisb

[unbuiltnautilus]

If you are changing prop size again you will also need to reconsider your motor choice. Better options for 55mm props are available but I am loath to start another longwinded debate about alternatives. I wish you well with the build but all I see is constant complications being imposed on the construction. I assume the model is 1/72 scale and about 92" in length? Just my input but, I have two models of similar size to this, SS Ohio 100", this has a single 60mm prop on a car blower motor at 12v, and Derrflinger a 96" battlecruiser, this is triple shaft with three Torpedo 800 motors on 12v and using a pair of Quicrun 880 speed controls. The first model is slow as befits a tanker, the second has a good turn of speed as befits a battlecruiser, must finish it though!
So feel free to take the advice given or don't, but the above works so why feel the need to tickle the specs yet again?!

[unbuiltnautilus]

Ah forgot, 45mm 4 blade Rivabo props, not sure about the pitch but most brass props have enough pitch to do the job needed of them.