Fixing the propshaft

I have an 8" Caldercraft s/s M4 propshaft.  At each end there is a small nut.  I assume these these nuts should be positioned at the ends of the outer shaft and not against the backs of the propeller and the universal coupling. But to allow the shaft to turn they must not be too tight.  If there were two nuts at each end I could tighten them against each other but as there is only one nut at each end how do I get them to stay in position to leave enough slack for the shaft to turn?  Superglue?

The nuts should be tightened against the back of the propellor and the coupling leaving just the slightest 'slackness' in and out to allow the shaft to revolve. Also there should be washers (brass, stainless steel, nylon or ptfe) between the nuts and the prop tube to take up some of the thrust and help seal the ends to prevent water going up the tube. The tube should also have either oil or light grease (many opinions about this!!) to help prevent water ingress.


Mike

Gribeauval is right on what to do but heres a visual for you just in case its still a tad unclear.

thread the prop or coupling to the shaft until its a tight ( but no so over tight you strip the thread as most fitting parts tend to be brass or bronze which is easily stripped by over tighting.)

the thrust washer should be at the bushing end of the shaft, then the nut then the attachment, simply using finger grip on the external part ( prop of coupling) and a spanner on the nut tighten the nut ( again don't over tighten for fear of thread stripping) 

You should have an even gap of the thickness of a bit of card between the washer and the prop shaft bushings, this is to allow the washer to move freely to seal the shaft in particular turn direction and to also allow for the motor armature movement, its not uncommon for some motors to 'pull back' a fraction or even be pushed back with the props push/pull... this i must point out is more common when using flexi drives rather then straight props shafts as those types tighten up in the winding as they spin, thus reducing the actual shaft length in those cases you should leave 1/8th inch gap for good measure , but its good practice to allow a small gap and also ensures that the shaft will not bind when under rotation as well as not prematurely wearing out the thrust washer with friction ( if to tight it can cease the shaft, over loading the motor and ESC, in an engine case will force the engine to stop causing other more serious issues)

the below photos show how it should look, although the last photo shows the gaps a little larger then needed but demonstrates the point.

Thanks to both - what a helpful forum this is - nobody has kicked sand in my eyes!

N:B a note on lubricating the shaft...

again as said before there are many options for lubrication, 

I've used machine oil  (151, or similar )  but requires regularly topping up ( practically after every run), and also runs the risk of putting oil in the lake on the first initial run. (seepage) 
Its best to fit oilers to the shaft when using oil as a lubricant, as pouring it down a shaft without is very tricky even is using a syringe, oil will just go everywhere! 

cost is a couple of quid every few months of regular running when using this product ( if running a steam engine then its a must anyway for the tool box)

My old man uses Castrol marine moly, which is thick and like a brown orange colour, he usually cleans the shafts every couple of months.
I used to use it until i brought my own tub of grease ( the tub was so big how can you not sponge off you dad huh!) so can vouch for its ability's. 

that tub was free it was liberated from work in the 70's! 

Now I use a similar moly but designed purely for marine applications, i had a shaft that kept leaking so got something thicker but ended up finding it was that good i used it now on everything (it can be white or black) It helps to reduce wear and corrosion as well as providing a very good seal up the shaft as well as also aiding in dissipating heat that can generate at the top of the shaft if i'm running a very fast motor, i tend to only strip out the shafts at the end of a season so far no shafts have needed replacing since swapping to stainless steel ones, but my brass shafts have needed a rub down to removes smaller corrosion marks.

The smaller tubs usually cost around £6-10 ( depending on brand) first tubs still going after the last 6 years.

For anything that runs with a flexi shaft i use a small amount of the marine grease on the ends of the bushings ( again high wear areas reduced) but the main shaft is filled with teflon grease, this is simply due to the stuffing tube having a teflon liner.

Teflon grease is about the same price, but you will chew through more as a flexi shaft Has to be cleaned after every days running or it will rust its only made of mild steel wire cable after all so inserting into water = more maintenance, even more so when running in a salt water environment.

Salt water = shaft hell!! and thast means 'brackish' water too ( that's why now i only use stainless steel shaft and liners!)

I'm sure there are other lubrication that work just as well theses are the ones i use and have had no issues with over the past decade.

I'll be interested to hear others lubrication methods is they wish to share?

 RR

RichardaBeattie wrote:

Thanks to both - what a helpful forum this is - nobody has kicked sand in my eyes!

yeah.. we don't do that on this forum i run a 0 tolerance policy on greifing members. 

Remember there is no such thing as a stupid question, if you don't know its better to ask!  


RR