Tina :- Engine and Boiler Build

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sbwhart:

--- Quote from: loco on May 04, 2011, 07:33:17 PM ---help
I can build boilers but how do I put a photograph here???
Pete

--- End quote ---

This may help Pete

http://madmodder.net/index.php?topic=607.0

Stew

klank:
Trying to get back to the engine build - the con. rod. next.

"Read the manual!"
In the build handbook, there is a chapter at the end - a sort of "addendum" - devoted to another more recent published article - appearing in MEW in 2009 - by Harold Hall.
He is dealing with basic work for a mill and rotary table, and uses some of Tina's castings to illustrate some techniques. Specifically, how to machine a round section/tapered con. rod and how to use a rotab. to finish the small end (rounding it off).
In this article, HH publishes a table of lathe dial movements (after some complex mathematics and other good stuff) for "saddle [X axis] and tool infeed [Y axis] so as to obtain the required tapered shape of the rod for Tina.
Unfortunately, for me, they are for an imperial dial measurement lathe (mine is metric), but it is quite simple to convert them. All of the X axis "slices" are the same, so all in all it is not a difficult job to follow.
HH's finished result looks a lot better than simply "taper turning" with the compound slide off-set - it's a bit fatter in the middle than Stan Bray's original, but still looks good.

This exercise looked far more interesting than a fish belly flat rod - so I discarded that idea.

I decided to set - to and see if I could turn up the same form, starting with a suitable length bar of BMS - 3/4" X 5/8" - which I had in stock. (Not supplied in the kit).
Following HH's notes, the bar is marked out to show where the big and little ends will be, the material in between to be turned away to a round section of the max. dia. of the con rod.

Bar marked out :-

The extra length will be turned down to a pair of spigots.
The bar was pop-marked for a centre at each end and put up in the 4 jaw with a tailstock centre and wobbler, to turn true. :-

A 1/2" spigot was then turned up to the end mark, and centre drilled. :-

The same procedure then carried out for the other end, and the meat in the middle turned away slowly, holding the bar in a collet and tailstock centre - as per HH's recipe. :-

Now came the interesting bit, following a table of 26 dual dimensions in X and Y axis to gradually turn away the material on one side of the centre so as to achieve the desired taper.
It wasn't as daunting as I first thought, and doing it slowly with care, the basic shape emerged, working from right to left from the mid point.

It was then necessary to do some filing/wet and dry of various grades to remove the machining marks whilst rotating at the same set up - here is the left hand side virtually done. :-

The same procedure was then followed working from left to right from the centre, without changing the set up (I don't know why a spigot at the other end is necessary, unless the set up is turned around end for end?) :-

The middle is now nicely tapered each way.
This leaves two oversized blocks at each end, plus the spigots.
The latter were sawn off, and a quiet hour spent on the mill to reduce the big/small end blocks to the required thickness and drill/ream the holes for the bronze bushes carrying the crank pin and gudgeon pin. :-

Now its a question of rounding off the perimeter of what will be the "small end" - HH recommending setting this up in the rotary table.
I have to confess to being a real novice at using a rotary table - so the possibility of making a bish of what I have got so far alarms me a little. I think I'll have to read up on Rotabs. for Dummys first!

More anon.

Peter

klank:
I could not do a lot today, dentist appoitment interfered - such fun!

I decided to make use of a small home made receiver/adaptor with my rotary table.
This would allow the collet chuck to be fitted to it, thus holding the small end of the con rod on a mandrel, without going to all of the trouble in making "mounting fixtures" as shown HH's article.

After setting up everything to run true, I off-set the table by the appropriate amount and gently milled off the edges of the small end, taking light cuts around and increasing the down feed a bit at a time with an 8mm end mill. Here's the set up about half way through. :-

Two bronze bushes were turned up for the two reamed holes.
That bush in the "big end" is meant to be proud on both sides - according to the plan! :-

I will start on the main bearing castings tomorrow, toothache permitting!!

Peter

Rob.Wilson:
:clap: :clap: :clap: :clap: :clap: :clap: :clap: thats a mighty fine looking con rod Peter :thumbup:

Rob

saw:
Nice work :clap: :clap: :clap:

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