Propshafts

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Propshafts

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Viewing 18 posts - 1 through 18 (of 18 total)

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29 September 2008 at 14:58 #16156
Peter Nordsjoe
Participant
@peternordsjoe33686
HI,

I notice on some models the propshaft is home made. Usually with a little vertical tube soldered on to the shaft to help fill the shaft with oil. The store bought shafts seem to do with out this. Is it because they are sealed better?

What are the pros and cons of using a store bought prop shaft besides the price? Do they last longer, let in less water…
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29 September 2008 at 19:10 #16161
ashley needham
Participant
@ashleyneedham69188
Hi Peter. Firstly the oil tube, I think I can safely say there is a difference of opinion on the matter of lubrication for propshafts. The "standard" shafts you buy dont have this fitted due to cost reasons I suspect, and this may be due to the fact that most shafts will out live the boat they are fitted in by a factor of ten, or even eleven and a half. All prop tubes have water seepage, due to the lack of a proper seal at the water end, and the relatively large bearing/shaft clearance. This can however be minimised by having as small an end-float when adjusted up as possible.. ie, there is just a smidgen of play moving the shaft back and forewards in the tube. To my mind, tubes filled with oil will just emulsify over a period of time, and leak anyway, causing pollution and all that. Grease is the other alternative, but really only the bearings need this. It is not a good idea to pack the tube with grease as this can sap the motor of power by increasing turning resistance. Unless you have a lathe, and of course not forgetting the materials I should think it is not worth fiddling around making your own, or cost effective . Personally i would buy a standard propshaft, one of the ones with a nylon bearing at either end and a stainless shaft . This would need the most minimum lubrication, as effectively the water end is water lubricated, and just a smear of grease at the inboard end. I am assuming you want to fit this in an "ordinary" boat and not a nitro racer or something . Ashley
30 September 2008 at 08:33 #16169
Peter Nordsjoe
Participant
@peternordsjoe33686
Hi Ashley,

Thanks for the input. This is for the 1/24 Vosper MTB I am building. I "would like" to have a triple prop set up but realistically though I should probably go for a single motor setup being that this is my first scratch build!

If I know myself tho I will probably wind up with a dual hehe.

You suggested to me that the Graupner 600 ECO might be worth alook. Do you think two of them would be too much?

Pete
30 September 2008 at 08:56 #16171
Paul T
Participant
@pault84577
Hello Peter

Following Ashley’s excellent posting on prop shafts and his recomendation to use a Graupner 600 I can only add that at 1:24 scale you should only require one such motor. This will produce a realistic range of scale speeds without putting to much power or weight into the model.

Paul
30 September 2008 at 16:48 #16181
ashley needham
Participant
@ashleyneedham69188
Pete, how big is this boat? I ask because MFA recomend a Torpedo 850 for thier Spearfish boat which is a fair size, 40 plus inches (without looking it up) but this is quite a hefty motor… Ashley
1 October 2008 at 11:43 #16191
Peter Nordsjoe
Participant
@peternordsjoe33686
Hi Ashley,

It will be three feet long. But I just got some info that the fellows att hsl mouldings used just one G600ECO with a 35mm standard prop and a 8.4 volt or 9.6 volt Ni-Cad battery pack for their exact same MTB (GRP hull). So I guess that answers my question. Atleast for a starting point.

Best Regards,

Pete
9 January 2009 at 19:20 #1720
Peter Nordsjoe
Participant
@peternordsjoe33686
Store bought or homemade?
25 June 2011 at 08:57 #31149
Neville Taylor 1
Participant
@nevilletaylor1
Hi Peter,

I have only been a subscriber to Model Boats since 2008 to date. Can you tell me is there an item in any issue about the distance of a prop from the rudder? I am referring to standard through the hull straight prop shafts NOT the Flex Drives even though I intend to use a OS 81 marine and tuned pipe.

Regards

Neville

Australia
25 June 2011 at 12:08 #31155
Mark Beard 1
Participant
@markbeard1
The only thing I’d add is that an MTB will run at fairly high performance. The Speed 600 Ecos and 35mm props at 1:24 looks like a good match on paper, but if you did want to fit two, they would share the load, run at reduced slip and higher efficiency, and give you plenty of power to get up on the plane in the first place.
25 June 2011 at 13:55 #31159
Mark Beard 1
Participant
@markbeard1
As a comparison, the 1:16 Model Slipway Tamar, for which I’ve done extensive calcs for Ian Potts, is similar in size and runs two Speed 600 Ecos with 40mm props. Both are fast hulls, the MTB faster in scale speed.

Ashley, thanks for the low down on prop shaft lubrication, I was wondering about adding an oil feed to my Conserver build but with your sage words I’ll grease the in-board bearing and set the end-float carefully. The prop shaft is horizontal, so hydrostatic pressure will be trying to flood the thing through the shaft. But I have installed the motor mount leaving drainage to the lowest bilge point and am fitting a bilge pump which I plan to trigger with a level detector, so hopefully all will be well.

Edited By Mark Beard on 25/06/2011 14:03:09
25 June 2011 at 14:35 #31160
ashley needham
Participant
@ashleyneedham69188
Mark. There have been numerous discussions on this very subject and no one will agree whats best, we all have our preferences.

If I had a lathe and could make my own shafts, I would use commercial brass tube and turn some nylon bearings for it, making the outbourd bearing twice as long as per “standard”, in order to improve the water sealing properties. It wouldn`t be absolutely watertight of course, and you need some water to lubricate the bearing in any case.

I have used a thick felt washer inboard with some success…this can be nipped up a bit tighter than normal as its springy, without being tooo tight, and will provide a bit of extra sealing at this point OR I have also cut some nylon washers to use at the outer end, again, they can be nipped up with no play and still not restrict the shaft too much.

I would simply arrange so that any water leaking from the shaft is kept from running the whole length of the hull, and every 20 or 30 mins check and if neccesary suck out excess water.

I have several models with shaft-lines totally submerged and never bother to check normally ; In 2 hours sailing I may get a few dessert spoons of water in there, but if everything is varnished inside and the reciever is not actually at the lowest point, it can be ignored.

Neville. I dont think there is much in the way of rules for this, However it shouldn`t be too close or you have trouble getting the prop on and off

Ashley
25 June 2011 at 14:51 #31161
Mark Beard 1
Participant
@markbeard1
I have a lathe and the ideal solution I guess is a V-seal just outboard of the inner bearing. I’ll have a think, but with a bilge pump aboard that may just be over-engineering a tad.
19 August 2015 at 08:58 #59784
Neville Taylor 2
Participant
@nevilletaylor2
Hi Ashley,

Two years ago I bought two prop shafts from one of the advertized suppliers of boat equipment in Model Boats magazine, unfortunately I have moved to Tasmania and in the process have lost a part of one of the tubes. The dimensions:- are 5mm shaft threaded at one end and 640mm long. The brass tube is 485mm long and at the threaded end has a nut and a nylon washer. the other end is a ball bearing in a shell 20mm x 19 mm dia which has a lubricating tube fitted.

Are you able to help with the supplier of these shafts? I have been to most suppliers but cannot find ANY identical shafts.

Neville(2) Taylor

0042556750
19 August 2015 at 12:49 #59785
Colin Bishop
Moderator
@colinbishop34627
Neville,

If your shafts are over two feet long I would imagine they were made to special order. I don't think anyone advertises shafts that long.

Colin
19 August 2015 at 14:44 #59786
shipwright
Participant
@shipwright
Neville,

I have a large scale model of a destroyer. Last year one of the props snagged a hidden rock and the prop sheared off from the propshaft. As the propshafts were bespoke I had no choice but to find someone who could make a replacement. I measured them and made a drawing (using the drawing tools in Microsoft Word) and showed the dimensions on the drawing. I then contacted PropShop via email. They were very helpful and after one or two phone calls to clarify the specification they manufactured a pair of stainless steel shafts correctly threaded for my props. The cost was about £32 for 2 shafts but there is also a charge for P&P (for uk/Europe it was £4 but for Australia it is likely to be more expensive). I know it's obvious but it is important to make sure you have measured and specified the shafts precisely before placing the order.

**LINK**

Ian
20 August 2015 at 14:10 #59797
Dodgy Geezer 1
Participant
@dodgygeezer1
It's very simple to buy steel rod of the correct diameter off ebay, cut it to length with a hacksaw, and then thread each end with a die – also bought off ebay. Total cost likely to be in the region of £10. And someone with a home workshop could make one even cheaper…
20 August 2015 at 18:10 #59801
Kimosubby Shipyards
Participant
@kimosubbyshipyards
Neville,

you asked about propeller to rudder distances, so I had a quick search and this website might have an answer for you. It discusses the distances of the propeller from hull and skeg as well and about boss diameters too. Of course it's all to do with life sized boats, but maybe there's something for us to learn as well.

here's the address **LINK**

Kimmo

PS I hope nobodys' poor installations are shown – there are some dodgy looking set ups.

Edited By Kimosubby Shipyards on 20/08/2015 18:13:20
20 August 2015 at 18:56 #59803
Bob Abell 2
Participant
@bobabell2
Extra long prop shafts can be achieved by ganging up two or three standard prop shafts…….Using flexible couplings

Would look quite nice too?

Just passing

Bob
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