The Association of Model Submariners.

Would you like to react to this message? Create an account in a few clicks or log in to continue.

* THE FORUM FOR ALL THOSE INTERESTED IN BUILDING AND OPERATING MODEL SUBMARINES *



Join the AMS - Registered Forum users can become members of the AMS and it's free ...... To join send an email with your name , address and phone number to amstreasure@googlemail.com


For a guide to past events see the "Shows and Events" section.

Who is online?

In total there is 1 user online :: 0 Registered, 0 Hidden and 1 Guest

None


Most users ever online was 180 on Tue Nov 05, 2019 6:03 am

Latest topics

» Radio ideas -27Mhz
Prop RPM Help Requested EmptyMon Jan 17, 2022 1:35 pm by geofrancis

» Radio RSSI depth controller
Prop RPM Help Requested EmptySat Jan 15, 2022 11:30 am by geofrancis

» Mast mounted water level sensor.
Prop RPM Help Requested EmptySat Jan 15, 2022 1:52 am by geofrancis

» Newcomer to the forum?
Prop RPM Help Requested EmptyMon Jan 10, 2022 6:45 pm by Tom(ADMIN)

» Type II U-boat
Prop RPM Help Requested EmptyWed Jan 05, 2022 3:17 am by tsenecal

» Lipo cut off circuit - Practical Electronics magazine - November 2021
Prop RPM Help Requested EmptyTue Dec 21, 2021 3:40 pm by tsenecal

» bladder systems
Prop RPM Help Requested EmptyTue Dec 21, 2021 3:35 pm by tsenecal

» Looking for drawings and instructions for Hegi U-25 Kit
Prop RPM Help Requested EmptySat Dec 18, 2021 12:44 am by Telusboats

» Nautilus II by Robert Fulton
Prop RPM Help Requested EmptyThu Dec 16, 2021 2:20 pm by david f

Statistics

Our users have posted a total of 11579 messages in 1900 subjects

We have 941 registered users

The newest registered user is PaulBrown

3 posters

    Prop RPM Help Requested

    avatar
    BuxtonRob


    Posts : 18
    Join date : 2017-12-21
    Location : Derbyshire

    Prop RPM Help Requested Empty Prop RPM Help Requested

    Post  BuxtonRob Tue Jan 16, 2018 2:59 pm

    I am attempting to convert a Revell Type IX U Boat to RC.

    I have a 385 brushed motor and a (handed) pair of Raboesch 25mm diameter 3 blade props.

    What rpm range should I be looking for for the props? I assume i will need a reduction gearbox (from max 11,000 according to the motor box). So what reduction ratio do I need?

    Thanks for any advice.
    david f
    david f
    AMS Treasurer


    Posts : 2214
    Join date : 2010-11-10
    Age : 71
    Location : Cumbria

    Prop RPM Help Requested Empty Re: Prop RPM Help Requested

    Post  david f Thu Jan 18, 2018 9:54 am

    I always like to have 2:1 to 3:1 reduction in motors. (It limits current draw and is generally best if your props have the (usual) coarse pitch.

    Others would disagree with this particularly when brushless motors are used. (i.e they use direct drive.)

    Have you had a look at MFA como motors and gearboxes? A very good range and good service and they save a lot of grief doing gearboxes:

    https://www.theassociationofmodelsubmariners.com/t1400-mfa-como-drillls-motorsgearboxes-and-belt-drives?highlight=motors

    You also ask about gearboxes out in the water. I have never tried this but I think that David Merriman and Norbert Bruggen offer them. Seems like a good idea.
    avatar
    BuxtonRob


    Posts : 18
    Join date : 2017-12-21
    Location : Derbyshire

    Prop RPM Help Requested Empty Re: Prop RPM Help Requested

    Post  BuxtonRob Thu Jan 18, 2018 11:32 am

    Thanks very much for that. I think it will be the MFA 2.5:1 geared 385 motor in the WTC and just the 1:1 drive to twin shafts from the single motor output in the wet area.
    david f
    david f
    AMS Treasurer


    Posts : 2214
    Join date : 2010-11-10
    Age : 71
    Location : Cumbria

    Prop RPM Help Requested Empty Re: Prop RPM Help Requested

    Post  david f Thu Jan 18, 2018 2:57 pm

    That should be fine. Without having done it, I would think that the wet 1:1 drive will be OK. (Slower running so not too much water turbulence & friction)

    Using MFA gearboxes means that you can change ratios fairly easily too. Nigel has a post on here also about incorporating a shaft seal into the gearbox. (I haven't tried it.)

    About a 3D printed O ring fit - I don't know either. I'm old school (lathe!). Tim G is exploring this technology.

    There are some very good tips here on sliding O ring fit (one from John Redearth particularly.):

    https://www.theassociationofmodelsubmariners.com/t537p125-piston-ballast-systems?highlight=piston+tanks

    Andy L has a video on lathe machining WTC caps somewhere. Post on the Dive-In Facebook site and he will let you know, I'm sure.

    David

    avatar
    BuxtonRob


    Posts : 18
    Join date : 2017-12-21
    Location : Derbyshire

    Prop RPM Help Requested Empty Re: Prop RPM Help Requested

    Post  BuxtonRob Thu Jan 18, 2018 6:48 pm

    I have achieved a 'close sliding fit' for a 3d printed end cap, after some trial and error, and now have a version with an O ring fitted which looks as though it is compressing uniformly all round. I have come close to the 85% groove depth by blind chance.

    I haven't tested for actual watertightness yet as my 'trial fit' end caps were printed as hollow, to save filament until a reasonable fit looks OK. Of course, now I have run out of the filament I used so need to order some more.

    Don't have a lathe or the skills to use one, so 3D printing it is.
    avatar
    tsenecal
    Guest


    Posts : 168
    Join date : 2015-04-01

    Prop RPM Help Requested Empty Re: Prop RPM Help Requested

    Post  tsenecal Tue Jan 30, 2018 4:49 pm

    BuxtonRob wrote:I have achieved a 'close sliding fit' for a 3d printed end cap, after some trial and error, and now have a version with an O ring fitted which looks as though it is compressing uniformly all round. I have come close to the 85% groove depth by blind chance.

    I haven't tested for actual watertightness yet as my 'trial fit' end caps were printed as hollow, to save filament until a reasonable fit looks OK. Of course, now I have run out of the filament I used so need to order some more.

    Don't have a lathe or the skills to use one, so 3D printing it is.

    one suggestion i would make is to print using a higher temp filament than PLA... you don't say which type of filament you are using, but PLA's glass temp is too low for my comfort...

    https://www.youtube.com/watch?v=TTswoDnxYHs

    i have switched to PETG as the filament i use for anything that is going to be used directly. for items that will become masters for molds, i will use PLA.
    avatar
    BuxtonRob


    Posts : 18
    Join date : 2017-12-21
    Location : Derbyshire

    Prop RPM Help Requested Empty Re: Prop RPM Help Requested

    Post  BuxtonRob Tue Jan 30, 2018 8:28 pm

    Using ASA for this. Can be acetone smoothed (which should give a watertight skin) and can be glued with polystyrene cement, so can be glued to the kit parts as necessary.

      Current date/time is Wed Jan 19, 2022 5:30 am