Propshaft

[Paul TParticipant @pault84577]

Working on it now Bob but your drawing was difficult to import into CAD.

 

Bob the engineer??

 

Paul

[Bob Abell 2Participant @bobabell2]

Hello Curly

 

Why are you trying to import my drawing into your CAD system?……….I`ts that good eh?

 

Bob the puzzled

[Paul TParticipant @pault84577]

Bob

If I am to do an old fashioned drawing like yours then I thought it best to copy yours into the system and then make the appropriate changes.

Incidentally I have the perfect subject for your next build.

The iron clad HMS Warrior

Paul

[Bob Abell 2Participant @bobabell2]

Hello Paul

 

You`ve mentioned the HMS Warrior before………….and I declined because it had been the subject of a long monthly series…………..and it was a perfect replica!

 

In was then, that I came up with JDAW……………remember old son?

 

JDAW us coming along nicely now………………I`ve been making all the fiddly bitz `n` pieces……………….photo shortly

 

I could have drawn my Stuffing gland on CAD but the printer is playing up at the moment

 

Bob

[Paul TParticipant @pault84577]

Bob

 

Don’t need a printer to post a cad drawing old son, just convert to jpeg and upload it onto the site.

 

I had forgot about suggesting warrior before (medication induced senior moment)

 

Paul

[Bob Abell 2Participant @bobabell2]

How do I convert to a JPEG?………………This something new to me!

 

Bob

[ashley needhamParticipant @ashleyneedham69188]

the warrior is no good a s a subject , is it..no paddles!!!!  I was hankering after building an HMS Agincort…1870 ish or thereabouts, as it had seven masts ! an odd coincidence really , as the 1st world war foreign purchase battleship Agincourt had seven turrets, called Monday-Sunday, and not a,b,c…x,y,z etc  or was it coincidence?   Anyway, also by odd coincidence, when I took the lad to the Isle of Wight last year,,,,in the STEAMER INN in Shanklin, what is there in a large glass case?? but a model Agincourt…not a great model it has to be said, but modelled with “gumption” and of a fair size..  I have set of plans (copies) of the AGI, a mere 8 feet long……gosh, I could make it full plan size !!!   Ashley

[David WooleyParticipant @davidwooley82563]

Good subject  there  Ashley  The mid Victorian era  is a wonderful period  in warship building  and seldom visited by the modeler .HMS Achilles  captures my imagination , as the   statistics  made her quite an   extraordinary ship for   her time  . The largest ship in the history of the RN   ever to carry a full rig . This Chatham built ship had a main truck 175ft above the deck and it’s hard to believe now but carried a staggering 50000sq feet of sail . Each of the two cylinders was a huge 112 inches and was fitted to one side of the shaft with the condensers on the other having a stroke of 4ft driving a 24ft 6inch screw.  Curiously her three bearing fire director functioned electrically even  before Inflexible  could boast being the first with electric lighting.  Puzzling though it is  it never ceases to amaze even today how  her gun crews managed to load the massive 12ft 4inch long  9inch bore muzzle loading   bow and stern  chasers with their  250lbs shells  in a sea way.    I would say to you build  Agincourt. I still drool when ever  I see the Reverend Mowels  Warrior model .

Dave Wooley

[Paul TParticipant @pault84577]

Ashley

 

Why not build the 8ft version?

 

If overall length is the problem then build it in two or three sections.

 

This would be a real challange even for such an experienced model builder like you.

 

Paul

[ashley needhamParticipant @ashleyneedham69188]

Dave, I agree about Victorian era ships, there is almost every variation you could want, from warrior to the last pre-dreadnought, and in a nice selection of colours. Nothing more striking than that black/white/red or white`n`buff combination, or indeed the very dark grey of the later pre-war (1) ships. I think that the bow chaser guns would have been impossible to work in a seaway in practice, not only from the motion of the ship, but the likely ingress of water..as indeed were most of the lower set guns on these pre-dreadnoughts (due to inadequate freeboard) . My “fun” DEVASTATION looks particularly realistic if there is a bit ow wind blowing on the pond, as the bow is perpetually underwater….just like the real thing !     

 

Paul, I would LOVE to build a whacking great boat, but just do not have the time to devote to a project like that. I am firmly in the stand-off scale department for the time being(hence Shorty etc etc). In a few years when the lad is a bit more grown up, we will see. besides which, the more the merrier….You lot keep on coming up with such tantalising ideas that i just feel obliged to have a go..

BESIDES my poor Turbinia, which is now appearing to be quite ordinary aqainst the challenges of a large multi-engined cheaty hovercraft, or an Eckranoplan…….and now the lad is desperate for Jeremy Clarksons “toyboata”  from the top gear program (do a quick google on that one), and he wants at least the rear wheels driven so he can zoom on and off the jetty/beach….(but I have worked that bit out now)….and and and…

Ashley

[Paul TParticipant @pault84577]

Bobs Drawing of stuffing gland

 

My drawing revised to copy Bobs detail

 

Detail showing position of neoprene washers.

 

Paul

[ashley needhamParticipant @ashleyneedham69188]

really whats needed is a groove in the propshaft, a slightly longer bearing and a small “o” ring, thats whats used in other applications.   

 

I could see the stuffing nut needing constant attention unless able to be locked up 

Ashley

[Paul TParticipant @pault84577]

Bob

 

I will post a more detailed drawing tomorrow showing how the seal works.

 

Paul

[David MeierParticipant @davidmeier28154]

That is good Paul, I can see that by squashing the neoprene washer axially, by tightening the nut, you can adjust the amount of squeeze on the shaft. Where as you cant do that with an o-ring type seal.

 

David.

[Paul TParticipant @pault84577]

Hi David

 

I am glad that you understand the science involved but I have included the thrust washer to take care of the “squeeze” so that the cap nut can be fully tightened.

 

The long version is as follows: 

The water tight seal is achieved by the tight fit of the neoprene washer over the shaft.

To explain this system I shall go through a step by step build up of a prop shaft.

For this we will assume a typical prop shaft of 6mm dia shaft running inside an 8mm int/dia tube giving us a 1mm free play between the shaft and internal wall of the tube n.b. the sizes are only given to help demonstrate the principal as the system could be applied to any size of shaft upto 15mm dia.

1/ lightly grease the shaft over its entire length.

2/ Position the shaft within the tube.

3/ Push the bearing into place along the shaft and into the tube and fix into position.

4/ Push a neoprene washer with an internal dia of 5.8mm onto the shaft.

At this point the tightness of fit between the shaft and washer will cause the washer to deform slightly along the axis of the shaft. 

5/ Fit a thrust washer over the shaft and up against the neoprene washer.

6/ Fit a second neoprene washer exactly as the first.

7/ Fit a standard washer (this stops the cap nut tearing the neoprene)

8/ Fit and fully tighten the cap nut. 

The watertight seal is formed due to the deformation of the neoprene washer in its contact with the shaft and the thrust washer maintains a constant pressure allowing the cap nut to be fully tightened.

I will try and post some 3D drawings of this tomorrow.

 

Paul

[ashley needhamParticipant @ashleyneedham69188]

I repeat my previous question (I think), exactly how much water do these gushing propshafts let in??? for such drastic engineering solutions???   AND if they are letting in THAT much, there is something more basically wrong…or have I just been lucky with the shaft department??    and ???? for good measure  !!!!    Ashley

[Paul TParticipant @pault84577]

 

A simple demonstration of the principal would be to get a pencil (with a round shaft) and slowly push the pointed end through a plastic bag.

You will see that as the plastic reaches the round shaft it bends and flattens to wrap tightly around the shaft, but if you are careful and if the plastic is rigid enough the pencil will be able to rotate without the plastic turning.

The tight fit between the pencil and plastic makes a super watertight fitting and this is exactly what I am doing with neoprene washers on a propshaft.

 

Paul

[David MeierParticipant @davidmeier28154]

Thanks Paul. that is very well described. I like that principle a lot.( the neoprene washer, not the plastic bag)

David.

[Bob Abell 2Participant @bobabell2]

Thank you Paul

 

You`ve really gone to town on this one and put a lot of effort in!

 

To be honest, it`s very complicated and fiddly and I `ll stick to the good old grease method and live with the leakage!

 

Thanks a lot clever sod!

 

Bob

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