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Author Topic: I have an offset shaft!  (Read 624 times)

bwatman

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I have an offset shaft!
« on: February 25, 2019, 06:33:19 PM »


I am building the Crick Steam Launch 'Victoria'.
I have constructed the steam plant and installed the prop shaft.
I need to 'couple' the steam engine drive shaft with the prop shaft.
The Steam Engine shaft is horizontal and 5mm diameter and prop shaft at an angle of 6.3 degrees & 4mm diameter.
There is a 5mm offset between the shaft centres.
There is a 30mm gap between the two shaft ends..
It is possible to cut both shafts back to leave 10mm stubs on each, therefore max coupling length is 50mm with 10mm of
shaft in each end of the coupling to fix to.


Can anyone point me in the direction of a robust, flexible coupling that can handle the above situation?
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Jerry C

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Re: I have an offset shaft!
« Reply #1 on: February 25, 2019, 08:19:21 PM »

You don’t need to use a coupling as such. Instead use a dog drive which copes with a multitude of alignment issues and makes removal/refitting of complete plant simple.
Jerry.

derekwarner

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Re: I have an offset shaft!
« Reply #2 on: February 25, 2019, 11:19:38 PM »

Jerry, I think this Gentleman is telling us apart from the 6.3 degree of angularity, there is also a 5 mm off axis in height

As stated, the physical gap between the prop shaft and the engine shaft is 30 mm

So whilst I agree many such prototypical steam plants used simple dog couplings, the 5 mm in off axis height is concerning


The engine built is not mentioned, however it may be possible to lower the engine mounting within the hull?


following is from the Krick WEB page....[so it is a reasonable sized hull]


Scale 1:10, length 1177mm, Beam 253mm


Derek

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Derek Warner

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CGAux26

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Re: I have an offset shaft!
« Reply #3 on: February 26, 2019, 01:41:27 AM »

Any misalignment, angular or offset can cause vibration, which leads to bearing failures and damage to most all parts of the boat. 


To cure the angular and offset misalignment, can you shim under the engine?  Using thin brass plate raise the front a bit to correct the angular offset and raise the whole engine to fix the offset?  Then you could use a normal coupling.
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rhavrane

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Re: I have an offset shaft!
« Reply #4 on: February 26, 2019, 08:24:49 AM »

Bonjour,
I would suggest the "TOC" (in French) option : https://www.youtube.com/watch?v=C5ATzAKX_Ww or https://www.youtube.com/watch?v=iR2Y0FVZULw at 2'30"
You can adjust the length of the pins if you put 2 and the width of the holes for the angle.
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Bernhard

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Re: I have an offset shaft!
« Reply #5 on: February 26, 2019, 10:49:20 AM »

hi  try to look in this video ,,you can stop it..and see what i have don,, work tip-top


https://www.youtube.com/watch?v=j9DQvIM8WRY
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bwatman

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Re: I have an offset shaft!
« Reply #6 on: February 26, 2019, 11:04:02 AM »


Thank you Jerry C, derekwarner, CGAux26 & rhaurane for your input - much appreciated.
CGAux26, I should have mentioned that the steam engine output shaft is 5mm higher (offset) than the prop shaft.
derekwarner, the steam plant is a vertical boiler and Libra Engine from Clevedon Steam (a great bit of kit by the way).


I can shim up the rear of the steam plant to get the same 6 degree incline as the prop shaft and hence line them up and use a straight coupling. However tilted engines look odd to me and I do not know what the consequences are of running a plant at an angle.
Did any full size steam boats have engines installed on the tilt?
I would prefer to find a reasonable solution to coupling to offset shafts without too much mechanical strain on the system or increased vibration. It's a steam river launch so I do not intend to power my way around the boating lake.
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bwatman

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Re: I have an offset shaft!
« Reply #7 on: February 26, 2019, 04:19:05 PM »


Bernhard, nice model and thank you for your comments.
I am interested in your solution to solve the shaft offset issue.
Can you tell me what sort of coupling you used and where can you buy them.
On another matter, I notice on a number of steam engine output shafts, there is a fly wheel.
What advantage does a flywheel give? (on a model boat).
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Bernhard

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Re: I have an offset shaft!
« Reply #8 on: February 26, 2019, 07:50:41 PM »

Thanks.. sorry i cant explain this for you,,but this is easy to make a work ok,,



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muleears

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Re: I have an offset shaft!
« Reply #9 on: March 03, 2019, 07:40:49 AM »

Bwatman, it has been a long time since I posted but I did the same build you are and had the same problem.  The link below is to my build thread in which many of the folks that offer advice in your situation did in mine as well. I linked to the page where I was discussing my propshaft issue.  You may enjoy the other portions of the thread also as it is the same boat as yours.  Good luck!  :-)) :-))
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Cal
Tidewater Virginia, USA
Proud owner of:
90% complete Midwest Fantail Launch
75% complete Krick Victoria
75% complete Billing African Queen
Krick Alexandra
Lots of building, very little steaming!

bwatman

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Re: I have an offset shaft!
« Reply #10 on: March 03, 2019, 09:29:00 PM »


Muleears, thank you for your post.
I have read the link regarding your build of the 'Victoria' - very interesting.
I note that you first fitted a double loop coupling but never ran the prop with it, was this because it did not fit?
You had fitted a horizontal boiler so space was limited is that why you never went with it?
I have a vertical boiler so can fit a coupling up to 50mm in length.
Did you choose this type of double loop coupling after researching torque and application data? Is it worth a go in my build?
Your build log does not show your completed model, is it finished?
Thanks again and will continue to read your build log for any future build issues I may get.
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muleears

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Re: I have an offset shaft!
« Reply #11 on: March 06, 2019, 02:29:37 PM »

bwatman,  Unfortunatley my construction of the Victoria came to a halt shortly after the last post.  I have just recently been getting back to it.  I did not use the double loop. It was too long for my application and the diameter of the hole was larger than my propshaft so fitment was an issue too.  I currently have the two peg drive system and I believe I have solved my noise issue.  Hopefully I will continue that build log in the near future.  Good luck with your Victoria!
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Cal
Tidewater Virginia, USA
Proud owner of:
90% complete Midwest Fantail Launch
75% complete Krick Victoria
75% complete Billing African Queen
Krick Alexandra
Lots of building, very little steaming!
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