Threading Prop Shafts

[Revell WalkerParticipant @revellwalker82816]

I have a fairly good idea how to go about this, but is there any thing I need to heed about threading my own prop shafts from 3mm – 6mm brass rod? What size die would should I use for them and what thread pitch? Could I do this with steel landing gear wire?

Rev

[TelstarParticipant @telstar]

Hi Rev

I alway use steel for propshafts, Brass tends to be ‘notch sensetive’ that is is will break easily anywhere you cut a notch or nick in it, however if I remember correctly landing gear is made from Piano wire, which is a springy hardened steel, if so this would ruin dies very quickly.

As for size, metric dies are sized as the diameter of the shaft to be threaded, ie. a 4mm dia shaft uses a M4 die, 3mm shaft uses a M3 etc.   obviously you match the size with the size of thread in the Prop.

In UK (I think your the other side of the pond) M3, M4 or M5 seem to be the standard sizes for most props.   The pitch is standard for the metric dia

Hope this helps

Tom

[ManxmanParticipant @manxman]

Hi Rev,

Have to agree with Tom, also remember not to cut too much thread. make sure no thread ends up inside the bearing as it will ruin it in a very short time.

Cheers – Ken

[Revell WalkerParticipant @revellwalker82816]

Hi thanks for the info. So if I use the K&S wire, I’ll have to heat it up to soften the temper a bit?

Rev 

[amey dalviParticipant @ameydalvi33562]

I have made a model boat of cardboard and covered it with a plastic cling film can  you please give me further details about cabin ,sail etc.

[JC Uknz 1Participant @jcuknz1]

Since the brass and piano wire seems to come from the States I guess that you will find it matches the American system of threads and gauge which are a complete mystery to me , but should make life easier for yourself  I too use piano wire for shafting.

When I cut the thread on the shaft I do not reverse the die so that the thread gets slightly larger as it goes up the shaft and this helps to bind the shaft into the prop itself. .. assuming you are buying readymade props .. in which case you need a die to suit the prop.if it comes threaded.

[JC Uknz 1Participant @jcuknz1]

Amey Dalvi .. I would suggest better than clingfilm would be to paint it with several coats od ‘dope’ that model aeroplane builders use, else epoxy.  

Unless we know what kind of boat you have built it is hard to suggest cabin and sail details.  A lot of yachts simply have a flat deck without a cabin or others have a curved raised structure something like a ‘shoe-horn’. 

The mast should be a bit taller than the length of the boat placed at about 1/3rd from the bow and arrange the sail as two triangles down from top of mast to bow and stem.[back end of boat]   The ‘stern sail’ or mainsail will need to have a boom along the bottom of the sail an inch or two above the deck and the bottom rear corner of each sail needs a string back to the deck so you can adjust the angle of the sail relative to the centreline of the boat.   The sail is pulled in when sailing into the wind [taqcking]and let out when ‘running free’ with the wind coming from astern [behind] the boat.  How much you adjust the two sails relative to each other will help the boat to sail straight.  It is a question of balance between them relative to the hulls shape and resistance to going sideways. Letting the front sail [jib] out will likely make the boat go to the right and hauling it in will encourgae the boat to go to the left.  Balancing the sails coupled with the rudder angle is an art which most learn by trial and error with each boat we sail.

If you do put the amount of sail suggested you will need a keel with a weight at the bottom, purhaps a fishing weight attached to a flat sticking down from the hull.  It does depend on the shape of the hull, my latest boat simply has the weight attached to the bottom of the hull. If the boat goes out in strong winds you likely will need to make another smaller set of sails so that it doesn’t blow over all the time.

If you are going to sail on a river or open water I suggest a length of string to haul it back

[HS93Participant @hs9317166]

Just rember befor you rush out to B+Q for a dia It is not the readeley avalable dia you need . just try using a standard M4 bolt ,it wont fit you need a M4  0.7 dia which is  a fine dia , you have to go to a specilist  the likes of  http://www.chronos.ltd.uk/  or use a 4ba but  I like m4 better on 4mm ss.

Hs93

[TelstarParticipant @telstar]

 Hi …  HS93   I think you will find 4mm x 0.7 is in fact ISO metric coarse thread, the ISO metric fine thread is 4mm x 0.5 .  Data on most threads can be found at

http://homepages.tesco.net/~A10bsa/isofgo.htm

along with tapping drill sizes etc.

cheers Tom

[JC Uknz 1Participant @jcuknz1]

I threaded a prop shaft yesterday and cut it with my "3mm" tap and only on looking this minute I found it is 3mm x 0.5.  Then I checked my ‘Workshop Technology" Chapman Vol 1 and found that Metric Fine is only listed down to 8mm so I think 3mm metric coarse is a pretty exotic animal.

Even if you live in the States I think it is probably a good idea to work in metric.  I work with three systems for my sins .. metric, imperial, thousands/inch .. with the tools aquired over the years .. typical engineering practice of the older worker but we are coming around as we buy new gear 

[Paul TParticipant @pault84577]

Dear All

A simple and cheap prop shaft is a piece of pre-threaded stud bar which comes in all sizes from 1mm dia to 22mm dia. These stud bars are available in both R/H and L/H thread and can be found at any engineering / building supplier (even B&Q sell it)

For example I recently purchased a 1m length of 2mm stud bar from B&Q for the princely sum of £2.50. (as the man says "cheap as chips")

Paul

[Bob Abell 2Participant @bobabell2]

What about the bearings?…..and the ingress of water?

Just asking????/

Bob

[Paul TParticipant @pault84577]

Ah Bob

Trust you to ask a serious engineering question when I was just trying to help out some members who were looking for a simple prop shaft, I assumed that the problems of the tube had been dealt with.

However to answer you technical curiosity for a 2mm dia shaft I would construct the tube out of 3mm dia brass tube and add a lubrication tube at 90deg to the tube at approx mid point. I would close off both ends of the tube with brass sheet through which I would drill a 2.2mm dia hole. The holes would support the shaft and act as basic bearings (the shaft won’t go that fast or for that long to get hot or wear out) 

The tight holes would also keep the water out when in conjunction with the tube lubrication / stuffing and the shaft would be kept in position (relative to the C/L of the tube) with lock nuts at each end.

Ergo a cheap and effective prop shaft and lubricated tube with the bonus that the same principal can be used upto 15mm dia. (thats the biggest that I have ever built)

So Bob this is how you suck eggs.(as I know that you are a far better engineer than I am)

Take care my friend

10 – 10 Paul 

[Bob Abell 2Participant @bobabell2]

Blimey.!……..I feel a migraine coming on!

………and 2mm too!………….a bit too much like fuse wire to me!

Don`t like the idea of brass sheet at the ends!…….a long bush would be better!

Only pulling your leg……….since you`re pulling mine?

Bob the Engineer……..O.N.C.

[Paul TParticipant @pault84577]

Hi Bob

I don’t mind a leg pull

Paul ……M.S.c

[ashley needhamParticipant @ashleyneedham69188]

Hi all, on this subject, Ifound on a website some plastic (polythene I think) top-hat bushes, the object of which is to be a tight fit on a motor shaft, and the outer is a tight fit into a larger hole, the point of the xercise being to fit a larger gear wheel on to a small motor (it being an educational sort of site with gears etc)    The web address is at work and i am at home now so i will try to remember to get it on Monday, if there is any interest (they were a matter of 40p or so)

HAVING a number of unused 3mm shaft 25mm props all through drilled..ie no thread in them , and wanting to use them in future projects it struck me that these bushes..using the 5mm o/d and 3mm i/d size would be great instant bearings. Using 0.25mm thickness brass tube of 5.5mm diameter would give me the perfect tube to fit the bearings, it only remaining to drill out the inside to 3.2mm or something to provide a nice fit for the brass 3mm shaft. (remembering the original hole is supposed to be a tight fit, and you always have to drill slightly oversize in soft plastic)…and the prop would be soldered on to the shaft with soft solder..the props being one-peice items in brass. From the other point…I should think ordinary soldered up brass props would be ok for this, as they would have been assembled with a high melting point lead/silver/whatever and so if you were to drill the thread out, they could be simply soft soldered straight on to plain 4mm or whathaveyou brass rod…no threading involved.

Polythene bearings would of course be water lubricated at the wet end and just need a drop of vaseline or something at the other.     Ashley

[Revell WalkerParticipant @revellwalker82816]

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