Stuart Turner 7a restoration project

[half whitParticipant @half-whit]

[HopperParticipant @hopper]

Simple but effective!

Yes, home workshop work seems to be constant compromises with not the right gear or not the right materials available. Innovation is the order of the day.

Engine is looking good.

[half whitParticipant @half-whit]

Hi Hopper,

Thanks for the reply. I should have added a message with the last photo.

As you can see I have the eccentric rod inverted on the angle plate, shoulders cut and then drilled and tapped for the bolts. Sacrificial plate in between the angle and the rod.

Next job is using the slitting saw to part the lower and upper halves.

Not done it yet as unsure how the loose half will react as the saw completes its cut.

Will the metal fracture first and then “dance” around. Never used the saw on metal so looking for some help. how will it react or am I worrying over nothing?

Geoff

[half whitParticipant @half-whit]

Hi

Just been turning up the eccentrics for the reversing gear.

It was useful having the original eccentric as when mounted on an expanding mandrel I could shift it around in the jaw until the eccentric runs true. This set the machining for the two eccentric blanks. The two will bonded together using a suitable jig to align them correctly. One the the bosses will then be machined away

[half whitParticipant @half-whit]

[HopperParticipant @hopper]

Nice.

You can hold the offcut bit with a pair of pliers or a bit of wire down one of the screw holes if you are careful to avoid the slitting saw blade.

[half whitParticipant @half-whit]

Hi Pete,

Thanks for the reply.

The eccentric rods parted off easily so panic over. I was surprised how resilient the gun metal was right up to point where the slitting saw completed the cut.

The two eccentrics are now finished and will need to be bonded together to form the dual eccentric shown in drawing below. I have turned a male and female register on the mating faces to help with alignment on assembly. (Sorry yet more engineering sexism). I would imagine that I will be able to cobble up some sort of jig to align the two parts accurately but any help, from anyone, would be recieved gratefully.

So why is the angle 30. Is that characteristic of this engine and how accurate does the setting have to be?

[HopperParticipant @hopper]

Valve gear design is a dark art, subject of many books. And reversing gear more so. Probably angle is not critical on a model for display running. Within a few degrees probably ok I should think.

[JasonBModerator @jasonb]

30deg is quite common on small steam engines like this and is what I usually set mine to as a starting point even though I tend to run on air. Angle is not critical I just eyeball the angle of a hex driver in teh grub screw hole.

 

This is from my Fowler drawings, a bit of trig or these days CAD will give you the distance the location block needs to be from the ctr when the eccentrics are at the required angle.

[half whitParticipant @half-whit]

Ok sorted, nice one Jason.

[Author]

Posts