Twin Diagonal Diagonal Paddle engine

[Ian]

Hi, I am trying to finish off for my father a engine by Edgar T Westbury he has made most of it over a number of years but was never very happy with the operation of the reversing gear. are the dimensions give on the plans correct at 1 9/16" and 2 3/16" for the weigh shaft arm and the lifting link. He has made a model boat to put it in and it would be nice to see it out on the water sometime soon.

[derekwarner_decoy]

Welcome Ian.......I have a licenced copy of the original manufacturing Drawings, however have never built the engine. From this, I  am sure the Lawyers for Mr Westbury would not object to my posting extracts of his M9 Engine here , as they are for technical confirmation or explanation only

The Item 31 Weigh Shaft Arm and Item 32, Lifting Link do have the principal centre dimensions as you note of 1 9/16" and 2 3/16" respectively

I have also shown these superimposed as per the original Drawing over the reversing expansion quadrant

For your Dad to build the engine is a credit to his machining skills, however when you say he was not happy with the operation of the reversing gear, may need more explanation

Fifty years ago, the same dimensions would have been transcribed out on a blued surface, stepped out with callipers, the centre prick punched. The assemblies relied on tolerances on whole numbers with reamed holes & pins with a nominal dimension drawn however in many cases machined to fit the bore. If the dimensional geometry were just a few thousandth's of an inch out.... .......striction can occur

I suspect you find there is a sweet spot, where the reversing motion just slides over, and a tight spot elsewhere....this certainly is not uncommon on all steam link arrangements
 
The movement and operation of the reversing gear is probably the most dimensionally critical lot within the engine. Certainly, I see many 5" Gauge engines where during post assembly hot steam tests reveals an operational striction that was not apparent during hand movement

There would have been literally hundreds⁺ of the M9 engines built & happily ticking over & reversing

You could consider joining a Model Boat Club, & be frank with the staff that you have a glitch with an M9 engine......you may find a member or two with the same engine and a love for steam that is happy to see & watch your Dads engine & offer comment

Derek

[Ian]

Hi,

Thanks for the reply Derek, the engine has been ran on both air and steam and will operate in both the forward and reverse directions. The mechanism will travel relatively freely between the two positions, however when the engine is running there is movement of of the weigh arms. The plan was to lock both of these arms onto a shaft that would then be rotated via a linkage connected to a power driven version of the traversing unit.

Should I try to find a sweet spot in the rotation of the weigh arms when locked onto the shaft where the vibration in one cancels the vibration in the other or do you think there could be a problem elsewhere?

Ian

[derekwarner_decoy]

Ian......movement of the Weigh arms would indicate that the Weigh shaft is being driven. This certainly could be from an eccentric, and hence a form of timing geometry issue

I would not suggest any form of external locking of the components associated with the reversing gear

Near impossible to offer any other comment. Joining a Club & getting an experienced eye to look over the engine would be the best way to go

Derek

[Ian]

Hi,
It might be daft question but could it be as simple as changing the ends of the quadrant that each eccentric is connected to?

Ian

[derekwarner_decoy]

Ian....Item 30 is the one piece construction of the Expansion Link [quadrant] for the reversing function ....

It also serves for potential 'notching'....but lets not complicate the issue here discussing this

You cannot change the ends of something that is one piece construction 

Could you mean ...end for ending - top to bottom or reversing or flipping this 180 degrees?

You could remove any of 12 different components and reverse or swap positions, however this would be illogical as you still have not identified what the root cause of the issue is. Any such actions could further complicate  any understanding of your original question

Derek

[derekwarner_decoy]

Ian....

There is a member on the Model Engine Maker WEB site, who has built an M9 engine & wheel set

Unfortunately this WEB site appears as down today......have you attempted contact for builder/owners of the M9 engine via GOOGLE?.........you may find someone online that may help

Derek

[Ian]

I might try to make a flywheel so I can run each engine independent of the the other just to see one runs better than the other, also I should be able to check that the eccentric sheave are in the correct position for good timing.

Ian

[Ian]

I've done a few calculations on the timing geometry just to make sure the dimensions given on the plans are correct. It seems to check out and will mean that the weigh arm should only move a minimal amount (1 - 2 mm) when the engine is running. so I will now look at making sure the eccentric sheaves and the slide valve are in the correct position.

Ian

[andy]

I own such an engine. Nice toy.

Andy

[R.G.Y.]

Yes I built one, my first steam engine. Ran ok but never put in a boat, R.G.Y.

[Ian]

Have made a flywheel and have now reset the timing on both of the engines and they seem to run ok. One has a bit of a tight spot and it lets a little too much air escape past the piston I think. so I might strip it down to investigate further.

Ian