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[goingdown]

Hi,


I am mid way through a 1/350 rc conversion which requires exposed shafts and bracket.  I have noticed that both propshafts I have bought have not been 100% straight, which is ok if you have bearings at either end of a prop tube but not so much if the shaft extends beyond the tube to support brackets.   


does anyone have any recommendations for the source of really straight propshafts?  I wondered about drill steel but I imagine that would rust fairly quick.


Guy

[Geoff]

I have not tried this but believe there is a well known method to straighten shafts. I think you tap them with a hammer on a flat steel piece of metal - google it and see what comes up.


Cheers


Geoff

[Howard]

Hi Guy,
 If not try Mobile Marine Models they might make you some Brian and Ann are very friendly and helpful.
                   Regards Howard.

[Plastic - RIP]

I'd consider the exposed part length and make sure the enclosed length is much longer in comparison so any whipping of the shaft is lost in the longer length and the energy is soaked up in the grease - it'll probably be totally fine as long as you're not looking to thrash the model around - scale-ish speed of a battleship should be ok.

I tend to use very long 2mm shafts to get them mounted horizontally in the hull like in real life - I hate to see propshafts at 45 degrees with the propeller pointing downwards.    I glue my motors to the inside of the hull to get all weight as low as possible.

[coch y bonddu]

SHG/Model Boat Bits/Mobile Marines/Propshop/Deans Marine take your pick




Dave

[Allnightin]

You might like to consider using 2mm carbon fibre rod instead, especially if you are using the kit propellers so would be gluing the props to the shaft.  The rod is very good at returning to a straight configuration if flexed and is also very light which might help if overall weight of the model is an issue.

[Tug Fanatic]

You might like to consider using 2mm carbon fibre rod instead, especially if you are using the kit propellers so would be gluing the props to the shaft.  The rod is very good at returning to a straight configuration if flexed and is also very light which might help if overall weight of the model is an issue.

I have never tried carbon fibre propshafts but two potential problems occur to me:

1. Is carbon fibre rod designed to accept rotary torque?
2. What is the rubbing wear rate where it passes though non rotating bearings?

[Allnightin]

I have used 1.5mm CF rod as a prop shaft to drive 12mm diameter props in a small launch (HMS Mimi) without any problems to date.  The A bracket bearings are just bits of plastic tube and I haven't seen any appreciable wear developing so far but bear in mind that such a small model is very much a fair weather only prospect anyway.  I used 2mm CF rod as the drive shaft for parts of a conversion of a 1/35th DUKW to RC ( article to eventually appear in Model boats) with 0.3mm holes drilled through the rod to allow a brass pin to secure reduction gearing to the shaft and this has stood the strain fine with quite a lot of hill starts and other test driving to establish its capabilities - the eventual problem that developed was some of the gears  starting to slip which I suspect was more to do with how I did the gearboxes rather than any failure of the CF.  In the context of plastic kit conversions (apart perhaps from the big MTBs and PT boat) I would suggest it is fully up to the job.

[Colin Bishop]

Somebody recently posted on here that most bicycle spokes are 2mm in diameter.

I think the problem is that most 2mm shafts start off true but if not very well protected are easily slightly bent, particularly in transit. They are also prone to 'whip' in use, particularly if there is a slightly unbalanced metal prop on one end.

Colin

[Tug Fanatic]

I have used 1.5mm CF rod as a prop shaft to drive 12mm diameter props in a small launch (HMS Mimi) without any problems to date.  The A bracket bearings are just bits of plastic tube and I haven't seen any appreciable wear developing so far but bear in mind that such a small model is very much a fair weather only prospect anyway.  I used 2mm CF rod as the drive shaft for parts of a conversion of a 1/35th DUKW to RC ( article to eventually appear in Model boats) with 0.3mm holes drilled through the rod to allow a brass pin to secure reduction gearing to the shaft and this has stood the strain fine with quite a lot of hill starts and other test driving to establish its capabilities - the eventual problem that developed was some of the gears  starting to slip which I suspect was more to do with how I did the gearboxes rather than any failure of the CF.  In the context of plastic kit conversions (apart perhaps from the big MTBs and PT boat) I would suggest it is fully up to the job.

Hoping that you are still looking at this.

When using  a CF propshaft what shaft bearings are you using. I note that the A bracket is plastic but what about the shaft bearings?

[Allnightin]

First to correct what I said the A frame bearing is in fact a piece of suitably sized brass tube - I must have been thinking of a different model at the time.


The shaft tube bearings are also bits of thin walled brass tube inside another piece of brass tube acting as a spacer and the actual tube itself is polystyrene tube.   I needed to keep weight right down so this seemed the best solution.

[Tug Fanatic]

Thanks for that.

[goingdown]

Hi all,


Its been a while since I checked on this thread - I will be going with carbon rod as it maintains its straightness and has the bonus of being lightweight which is welcome when using it on a 1/350 cruiser with its minimal displacement.


Thanks


Guy