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 further details of any free events shown here also see the "Shows and Events" section on the forum

*2021 AND SOME EVENTS ARE BEING PROPOSED. Keep them coming and let us know the details! (amstreasure@googlemail.com)

;
;:;


Model Sub Weekend, 28th, 29th August. Bluewater Parkway, Greenhithe, DA9 9

Bournville Sub Day. Sept 2021 is looking likely. More details TBA.

Barrow in Furness Regatta and Sub day. Maybe in Sept 2021. Details TBA.

Who is online?

In total there are 2 users online :: 0 Registered, 0 Hidden and 2 Guests :: 2 Bots

None


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

Latest topics

» GRP end caps
Prop RPM Help Requested EmptyTue Jul 20, 2021 9:31 am by david f

» WW2 mini sub build
Prop RPM Help Requested EmptyTue Jul 20, 2021 9:15 am by david f

» Good 3D beginner's tutorial
Prop RPM Help Requested EmptyFri Jul 16, 2021 3:14 pm by david f

» Looking for drawings and instructions for Hegi U-25 Kit
Prop RPM Help Requested EmptyThu Jul 15, 2021 1:25 am by Telusboats

» Merit 1/35 X craft
Prop RPM Help Requested EmptyTue Jul 13, 2021 3:54 am by tsenecal

» UHF radio control for submarines (openLRS, LoRa, FSK etc. on 458Mhz and 433Mhz )
Prop RPM Help Requested EmptyMon Jul 05, 2021 10:43 am by david f

» The workings of a sheer line submarine
Prop RPM Help Requested EmptyWed Jun 30, 2021 9:03 am by subkraft

» Bonjour from France.
Prop RPM Help Requested EmptyMon Jun 28, 2021 1:43 pm by Tobyledog

» Underwater navigation using UHF ?
Prop RPM Help Requested EmptyFri Jun 25, 2021 5:46 pm by SimonH

Statistics

Our users have posted a total of 11427 messages in 1877 subjects

We have 930 registered users

The newest registered user is Aniello

    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 : 2172
    Join date : 2010-11-10
    Age : 70
    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 : 2172
    Join date : 2010-11-10
    Age : 70
    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 : 154
    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 Mon Jul 26, 2021 3:27 pm