Class 800 Gauge O CNC Parts

[murrayec]

I'm doing the valve gear, wheel weights & break gear on a Class 800 Gauge O kit- no. 801 'Macha' for a chap. A lot of parts for this are not supplied with the kit so have to be fabricated and decided to experiment with cutting them out CNC style!!

Some mods to the crosshead and cylinders is required as the kit seems to be based on LNER valve gear and the 800 was a little different

I took many photos of the model and imported them into cad and worked out the design for the crosshead system, a chassis hanger assembly to hold the H frame crosshead bar that was more applicable to the class. I also worked out the break stuff from 800 drawings and then got machining....

This is the machine now installed in a dust/noise cabinet- it's hard still to stay in the room when the spindle is up at full speed

But it's fascinating to watch the parts appear out of the sheet of metal, this is a shot of the break hangers, wheel weights and crosshead hanger assembly in .5mm brass

and complete

Break shoes in 2mm Drelin being cut out, this is easier on the ears as the spindle is running much slower

and complete

This is the crosshead H bar parts and distinctive 800 crosshead bracket in .4mm nickel silver as these wont be painted

All worked very well, looking forward to sticking it together.........

Eoin

 

 

[murrayec]

Everything removed from the sheet, all the tabs removed by filing, holes broached up to size, and ready to assemble, on the left top is the steam valve rod guides, next to the right is crosshead stuff, next wheelweights, back down left are the crosshead bracket support to the chassis!.... you'll see in a while...

Break shoes were .5mm slotted to fit with .5mm pin onto the hangers

Break roding bars, the brass cross bars are filed a little on the edges to fit the bottom hole in the hangers, .6mm NS rods will be used for the lateral rods

Complete, and will be attached to the chassis next time....

This is the valve gear kit that was supplied with the model, it's very close to the 800 stuff and with a little tweaking should be quite acceptable??

Eoin

 

[murrayec]

This evening I set up to check one of the cylinders parts to see how it is going to work!

Steam chest rod guides folded up and ready for soldering, on the left is a 1.5mm copper rod which will be fixed into the front of the steam chest.

Guides on with 180deg solder

Crosshead slide bar hanger folded up and soldered with 180deg solder

NS 'H' slide bars being soldered with 180deg solder, this was a fiddly one but the half cut line down the components helped to line it up under the clamps.

Crosshead clamps being folded up for soldering

Clamp soldered up and onto the crosshead/conrod and a completed slide bar- the rod soldered on the end is the support pin that goes into the cylinder body.

Test assembly of one side- the hanger and slide bar are fine but the crosshead clamp is off centre and will foul the combination lever going up to the steam chest rod- some modification to the clamp will be required to move it in towards the chassis a bit. Otherwise quite happy how all is working.....

Eoin

[popeye]

Very nice. It's all the detail parts that make all the difference. 

[murrayec]

Thanks popeye, yes detail parts give it scale

So adjustments made to the crosshead today to give clearance for the combination lever, it's at the max it can be moved inwards but one can see in the photos the lever can just get by, in final assembly the lever will have a slight bend to give further clearance.

It's funny how things work out!- by having to the make changes here has led to a better way of assembling the crosshead, so now it can be dissembled far easier in the future, than first designed!

All the other gear for this side cleaned up n ready- a few more parts need to be made before this can go on- I looking at the pivot supports for the expansion link, radius rod and the lifting arm, going to use crank pin bushes here. The 800 has very distinctive fittings on the chassis out rigger here and thats what I'm making next??

Eoin

 

[Noel]

Superb model engineering master class.

[murrayec]

So a bit more parts cut and the valve gear kit cleaned up with files and a fixing plan is worked out.

This is a new combination lever cut out- on the left, it's shorter than the kit one- on the right, and of thinner material which will help with the clearances, these parts will be .8mm steel revetted together.

Crank pin bushes and 12BA screws will fix the expansion link and radius rod to the chassis and the cut circles are the 800 detail parts around these fixings. The lifting arm will have a steel rivet soldered on to run in the radius rod slot. The eccentric rod will be 14BA screw fixed and again the NS cut circle is 800 detail part to be soldered on, the rod is very plain and should have a flute down the middle- so I decided to cut a flute in it- see below.

One done, second one to do.

Tender break gear cut out, cleaned up, holes sized and

delrin shoes assembled on their hangers, .4mm NS was used for these parts

Eoin

[Mayner]

Hi Eoin

What make/model of cnc profile milling machine are you using? 

[murrayec]

10 minutes ago, Mayner said:

Hi Eoin

What make/model of cnc profile milling machine are you using? 

Hi Mayner

It's a Stepcraft 420 with a Kress router/spindle- it also takes a Dremel, the 450 has a working area of about A3 size. They have other options for this machine- wire foam cutter, knife cutting and 3D printer, and fourth axis option- rotary table.....

http://stoneycnc.co.uk/stepcraft-overview/

There is also a photo at the start of the thread

Eoin

Edited July 1, 2018 by murrayec

[murrayec]

Today I erected the tender break gear.....

The chassis holes for the hangers was worked out very carefully, as the chassis sides were not identical so I used the height gauge to measure and mark the holes from the axles. The chassis has a slight twist in it which also caused some line up problems after the holes were drilled!

After some work with a files, a broach and 'gentile persuasion' I set about soldering it together with 180deg solder.

I left a good gap on the break shoes and outer lateral break rods so that the wheels can be removed for the painting work.

Thats the tender chassis work complete,

Eoin

[murrayec]

This evening I got the 800 trial valve gear side erected, after steel riveting, 14BA tapping and a few nuts soldered it all came together.

These are the 800 detail valve parts soldered on to the chassis plate, those cheese head screws are temporary, brass countersunk ones will be used finally.

The crosshead is going to miss the combination lever- phew!

The slide bar chassis hanger is now soldered in place and the slide bar needs a bit of a trim here.

The valve rod is a bit sloppy in its cylinder and I'm a bit concerned as to how it will work under power! but cant test run it until the Loctite sets overnight on the return crank- then I need to shorten the crankpin screw as it fouls the eccentric rod! The return crank should be soldered to the crankpin, but the whole thing needs to be dissembled for painting- soldering will be done after the painting is complete.

Eoin

[popeye]

Looks very complicated.

If this does not run smooth it might cause some drag. 

[murrayec]

Hi popeye

It all runs smoothly on test but the valve rod does have to much slop in its bore, as suspected! I will work out a sleeve solution on the second cylinder and then apply to both.....

Here are a a few photos of the engine break gear and wheel balance weights erected, these cast iron wheels are really nice it seems such a pity to paint them!

The break gear is 180deg soldered and the wheel weights were epoxied on, again like the tender I left a generous gap between the break shoes and wheel tyres for wheel removal for the painting work.

Now to complete the other side valve gear.....

Eoin

[jhb171achill]

Oooooooooooohhhhhh!!!!!!!   Where's me smelling salts!!!

[Weshty]

Stunning piece of work there Eoin, it will be some animal in "O".

[popeye]

Very nice. The balance weight on the middle wheel looks bigger than the others, was this normal?

[Broithe]

1 hour ago, popeye said:

Very nice. The balance weight on the middle wheel looks bigger than the others, was this normal?

The 'end wheels' just have half of their respective interconnecting rods to cope with, the centre wheel has two halves of the interconnecting rods and about half of the con-rod from the piston imposed on it.

[murrayec]

2 hours ago, Broithe said:

The 'end wheels' just have half of their respective interconnecting rods to cope with, the centre wheel has two halves of the interconnecting rods and about half of the con-rod from the piston imposed on it.

Spot on Broithe

Could not have said it better myself, a bit of an engineer in yeah...

Eoin

[KMCE]

2 hours ago, Broithe said:

The 'end wheels' just have half of their respective interconnecting rods to cope with, the centre wheel has two halves of the interconnecting rods and about half of the con-rod from the piston imposed on it.

True, but what is more interesting is that the centre cylinder operates on the front axle which has the crank and valve eccentrics  built in.  The axle also has associated counterweights take up this imbalance . 

Thus, why weights on the crank and wheel - unless the front one is cosmetic?

[Mayner]

11 minutes ago, KMCE said:

True, but what is more interesting is that the centre cylinder operates on the front axle which has the crank and valve eccentrics  built in.  The axle also has associated counterweights take up this imbalance . 

Thus, why weights on the crank and wheel - unless the front one is cosmetic?

The balance weight on the leading drivers would most likely compensate for the loading from the coupling rods, the inside crank for the cylinder

I would be interesting to work out the relative positions of the driving cranks on a 3 cylinder loco like 800 or a Royal Scot, perhaps a visit to Cultra to solve the mystery?

Edited July 11, 2018 by Mayner

[KMCE]

12 minutes ago, Mayner said:

The balance weight on the leading drivers would most likely compensate for the loading from the coupling rods...

That makes sense!

 

The cylinder positions are as below if that helps with the centre cylinder well forward to allow connection to the front axle.

 

Another question is - are the wheels quartered, or is the system set up on 120deg given the three cylinders?

Eoin - How are you setting it up on the model?

[David]

The balance weights on the fore and aft drivers are approximately the same size and since the rear axle only deals with the coupling rod, it is probably reasonable to conclude that the forward driver weight only equates to the coupling rod it supports. 

[murrayec]

22 minutes ago, KMCE said:

Eoin - How are you setting it up on the model?

Hi KMCE

It's quartered, the chap who built the chassis has the left side leading

The wheel balance weights are essential on large wheels to counter-balance the weight of the crankpin boss cast in the wheel, the crankpin, and the motions.

The inside cylinder is far ahead of the outside ones because the drive is taken from the front axle and the radius rod driving the valve needs to be as long as possible to set up the correct motion angles with the combining and anchor links to control lap and lead to the valve ports.....

Eoin

[Broithe]

Balancing of reciprocating engines is rather more complicated than it looks. On steam locos, nobody ever seems to take much account of the second order vibrations, possibly just relying on the general mass of the machine to reduce those effects. In lighter machinery, particularly motorbikes, there may often be one or two balance shafts running at twice engine speed.

[murrayec]

Yes Borithe

the main problem with steam loco design, - build it big and hefty, replace it when it comes loose, and no need to change the existing design 'because it works'. This is the design ethos that got steam a bad name...

Motor bikes got smoother when the Japs got involved with their lightweight engineering and more modern ways of thinking! I have a few British made 'Thumpers' - a 1961 BSA C15T 250cc single is the worst- at about 30mph the vibrations make it difficult to hold the bars, above that it smooths out again, then close to 60mph about as fast as I dared to go- your vision blurs, there is a brand new Alpha big end bearing kit installed n all!

Eoin

[Broithe]

24 minutes ago, murrayec said:

Yes Borithe

the main problem with steam loco design, - build it big and hefty, replace it when it comes loose, and no need to change the existing design 'because it works'. This is the design ethos that got steam a bad name...

Motor bikes got smoother when the Japs got involved with their lightweight engineering and more modern ways of thinking! I have a few British made 'Thumpers' - a 1961 BSA C15T 250cc single is the worst- at about 30mph the vibrations make it difficult to hold the bars, above that it smooths out again, then close to 60mph about as fast as I dared to go- your vision blurs, there is a brand new Alpha big end bearing kit installed n all!

Eoin

A properly balanced engine is not just 'nicer', it is better in every way - the loads on the bearings are lessened, things last longer, and not just because they aren't shaken off.

God knows what was going on in the float chamber of a boneshaker bike..?

It's not many years ago that a ferry journey was accompanied by the constant jingling of the duty-free bottles - (although it has its current issues) Ulysses is notable for having almost undetectable engine vibration.

Edited July 11, 2018 by Broithe

[murrayec]

We had a boat, not the size your talking! it had a Volvo Penta Diesel- if you ran the engine for any considerable time and one was sitting down, one got 'white Bum' you know like 'White Finger' using a B&D mouse sander...

Eoin

 

[Mayner]

21 hours ago, Broithe said:

Balancing of reciprocating engines is rather more complicated than it looks. On steam locos, nobody ever seems to take much account of the second order vibrations, possibly just relying on the general mass of the machine to reduce those effects. In lighter machinery, particularly motorbikes, there may often be one or two balance shafts running at twice engine speed.

From the early 1900 up to the introduction of the Britannia Pacifics in the early 1950s 3-4 cylinders was basically the standard for large British express steam locos due to the improved balance of 3-4 cylinder layout and reduced damage to the track.  The trade off was increased build and maintenance cost compared with a 2 cylinder machine.

The 10 GSWR 400 Class 4-6-0s were introduced in preference to building more large inside cylinder Class 341 Class 4-4-0s as the 4 cylinder layout of the 4-6-0s was considered to be easier on the track than the 341 Class.

The GSR eventually rebuilt 8 of the 400s to a 2 cylinder layout and scrapped the un-rebuilt locos to improve reliability and reduce maintenance costs. In the early 1920s the LSWR N15/GSWR 500 Class/GWR Hall/LMS Black 5 basically set the UK & Irish standard for the modern 2 cylinder mixed traffic 4-6-0 capable of express passenger and goods work, BR appears to have adapted the 2 cylinder layout for the Class 7 Britannia pacifics as they were considered to be mixed traffic rather than an express design, the solitary BR Class 8 Pacific the Duke of Gloucester which had a 3 cylinder layout similar to the 800 & Vs Class rather than the 4 cylinder layout used in the LMS Class 7 & 8 pacifics and GWR Star/Castle/King Class 4-6-0s

[murrayec]

Completed the second set of valve gear for Macha......

This is the gear coming together, a small brass tube was used to remove the wobble in the steam valve rod, two were made to tighten up the mechanism so that the combination lever would miss the cross head- it worked!

 

Nearly all the gear ready to go on

Front steam rod housing installed in steam chest and combining link had a little kink added for more clearance

Counter-sunk screws installed in chassis detail parts...... and it's complete!

Now the test run with both sides erected??

Excellent it runs fine, all the gear does what it's supposed! but we have a wobbly wheel at the back end causing a bit of a stutter- the whole assembly will be coming apart again for painting so hopefully the wheel can be sorted then.

Job is complete

When I get the body back on I'll post a few photos

Eoin

[jhb171achill]

Eoin, you've made me run out of smelling salts now, and the drooling is becoming a problem....................................................................!

Edited July 28, 2018 by jhb171achill

[murrayec]

......and here is Macha with body back on, ready to go back to its crew for painting and finishing.

 

Edited July 28, 2018 by murrayec