Hick Crank Overhead engine

[ettingtonliam]

Yes, split bearings were commonly called 'brasses, and your 'cotter pads' were 'gibs', the whole being known as a gib and cotter joint.

Having gone through the process 16 times for the coupling rods and connecting rods for my 7 1/4" gauge Locomotion model, I wish I'd seen your system first!

[AVTUR]

The major problem I had with the cotters was collecting them after the final cut with the slitting saw. Sometimes they just sat in the gap or on the cross slide. Other times I had to search the tray under the lathe. It is always wise to clean out the tray before doing such work!

AVTUR

[AVTUR]

I am going to try to get this on to the forum site before Christmas!

The connecting rod bushes, brasses, although very much smaller, were be produced in the same way as I had planned to make the crankshaft bushes two years ago. And I had similar problems. They were made from COLPHOS 90 bar. For the halves that sit against connecting rod the bar was milled to a rectangle twice the height of the half, hole drilled under size and the sides slotted to take the strap and connecting rod. The result was the halved by milling away the surplus on the strap sides. The halves that were held by the strap were just turned, the centre with a parting off tool, drilled with same size drill and halved as above. So far so good.

Fixtures were made to hold the mating bushes so that they could be reamed to size (which would have been a mistake) and faced to length. The thickness of the metal at the end faces is small. On the two smaller bushes it is 1/64” and the fixture did not give adequate support. Another set of bushes were made and this time they would by faced to length and bored to size when assembled on the connecting rod.

Getting the lot to fit took time. A lot of small fine filing work was done on the end of the connecting rod, the straps and to the cotters. I guess it would have been easier to work to looser tolerances but... In the end the pads would fit the straps if the straps were just squeezed slightly by finger pressure. The bushes, assembled, were then filed to length and the bores opened up to suit the trunnions on the crosshead and crank pin using a clockmaker’s broach. This allowed the small end bushes to be line “reamed” (sort of).

Obvious there is no interchangeability of parts so all the bits had to be matched. I generally used small centre punch marks to match parts but this is out of the question with the bushes so each bit of the assembly is painted with different coloured permanent marker (hence the blood on the assembly). Trouble with this is that the dried ink easily rubs off so the marking is repeated after every assembly. All this work was done in a large document box lid since I would never find anything that fell off the bench.

The crank web and pin were made without difficulty. Once again the pin’s bearing surface had to be produced used a parting off tool. The broaching of the web keyway was easy and the web fits snugly on the shaft with its key.

At this point problems return. More should follow before the New Year.

Happy Christmas

AVTUR

[AVTUR]

This is just a short posting.

I am still working on the model which is nearly finished. However progress has been slow because the real world is making demands on my time. I have also been side-tracked by starting another model.

A proper progress report should be posted during the autumn (fall).

AVTUR

[Admiral_dk]

Good to hear that you still are around 

Per

[GWRdriver]

Excellent work and very informative.

[AVTUR]

The below was written over a year ago and held back for lack of photographs. You will notice there are not any!

A year has passed without me posting a progress report. I have been making slow progress but life, not health, has returned with a vengeance since lockdowns were removed. I have not helped matters by taking on more responsibilities and starting another project.

Having made all the piston rod and connecting rod another trial assembly was made. This time it was to determine the position of the piston rod guide which sits in the fork of the connecting rod. Although the piston rod lined up with the crankshaft the guide was nowhere near its bosses on the adjacent standard [photograph attached]. Since everything else lined up the only way I could see how to cure this was to lift one foot of each standard and slide them across the bedplate. This struck me as an awful lot of work with new parts probably needed along with a lot of thought. There was an alternative, accept the misalignment and use a plate between the standard and guide bosses to offset the guide. The model would not look right to anyone who knew the engine but it would allow me to finish it. So a plate was produced with its own bosses silver soldered in place. The bodge was successful but quite a bit of delicate filing had to be done to prevent the connecting rod from hitting the guide bosses (this was with a couple of horribly blunt files that had never seen steel).

The final bits of the model were then tackled, the steam supply throttle plate, its rod and bushes along with the governor die block and various linkages. This work allowed me to use my nice new little lathe. The only difficult bit was the throttle plate, I gave it a lot of complex through and realised all it was was a slice cut from bronze bar at an angle of about 30o, drilled for the rod and filed to shape.

Finally the steam and water pipes were bent to shape and silver soldered to their flanges. I found there was not enough room on the water pump for one of the flanges so the pump will have to be modified.

At this point, last (now 17 months ago) autumn (fall) all the bits were put back in the box since another model had priority.


I have posted this out of shame. The model is dismantled and some time ago I started painting it. Other things have got in the way including two models, a 5" steam loco (which I will never finish), and a Saturday model, a Stuart compound marine engine.

AVTUR

[Jo]

What ever it is it must be catching... I have hardly been in my workshop for a couple of years. I did manage to make a list of easy things to do when I wandered in there earlier and even chucked up the material in a collet to turn up a couple of main bearings. I wonder how long it will be before I do those 

Jo