7 1/4 inch Fowler 3F Progress

[ukjimoo]

Hi all

I have finally managed to get some photos onto photobucket of our pair of 7 1/4inch 3F Jinty's in their early stages.
I hope they are of interest.


The wheel patterns



A pattern and a wheel casting ready for machining


A wheel casting set up in the 4 jaw in order to machine the back faces and bore at the same setting.


The wheel turned around and mounted on a mandrel in order to machine the front faces and tyre profile.
The mandrel was machined a good fit in the bore and left undisturbed in the 3 jaw until all 12 wheels were complete to maintain concentricity. It was quartered with a hacksaw to a depth of half the bore and drilled and taper tapped so that it would expand with the tightening of a bolt. A drive dog can be seen at the 10 o'clock position. This is welded to the mandrel with a stud and locknut which is removable to aid mounting and removing the wheel on the mandrel which can get rather tight after being expanded.


A pair of assembled frame sets.


A frame set with horns and axle boxes fitted.


Chewing out the valve chest cavities.

Jim

[ukjimoo]

Hi all

Does any one have any suggestions on a good way to secure the wheels to the axles. As you can see from the photos we have used one piece axle boxes with oilite bushes so i would prefer a method that would allow for wheel removal should the bushes wear in the future.

The axles are 1" diameter with the ends turned down to 7/8" to a depth of 1" to suit the bore in the wheel.

Many thanks
Jim

[drjohn]

Hi Jim

I bore a 1/16" hole half in the wheel and half in the axle and insert a roll pin and loctite the whole shooting match.

With my original Simplex, I had to remove the rear wheels to replace the bearings, and with a puller and a quick tap with a hammer, it wasn't a problem, then of course replacing the wheel after re-bushing the bearings was easy as the hole basically re-quartered the wheel.

DJ

[albert]

Hello ukjimoo
From past experiance I found oilite bushes must have a very hard axle,they wore down a steel axle very quick,with no wear in the bushes.
Personally I would use cast iron for the bushes.
Albert.

[ukjimoo]

I bore a 1/16" hole half in the wheel and half in the axle and insert a roll pin and loctite the whole shooting match.

I dont think i would be able to get to the rear of the roll pin to tap it back out as the wheel is mounted up to a shoulder. Is yours the same John?

Just a thought, but could the pin alternatively be a grubscrew screwed into a taper taped hole and loctited?

Jim

[drjohn]

Whatever, Jim, but you don't need to remove the roll pin as long as it is parallel with the axle, when you pull the wheel off, it will come out.

DJ

[drjohn]

A picture speaks a thousand word - this might make it clearer Jim. The wheel is loctited onto the axle and the pin hole drilled after the loctite has gone off. The loctite holds the wheel on the axle, and the pin prevents any rotation to upset the quartering should the loctite fail.

DJ

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[ukjimoo]

Whatever, Jim, but you don't need to remove the roll pin as long as it is parallel with the axle, when you pull the wheel off, it will come out.

Oh yes, of course it would - i'm with you now.

I suppose a screw would safegaurd against the wheel moving sideways if the loctite failed but on the other hand that shouldn't happen and a pin would probably provide a better location.

[drjohn]

Jun 2, 2010 11:18:30 GMT ukjimoo said:

I suppose a screw would safegaurd against the wheel moving sideways if the loctite failed but on the other hand that shouldn't happen and a pin would probably provide a better location.

The pin is also less conspicuous than a screw.

DJ

[isc]

Think its called (by some), a Scotch Key, seem to remember seeing this on full size NZR locos. Solid pin not a roll pin.isc

[Shawki Shlemon]

I use the same method as DJ ,but I use solid pins and on drivers I use two pins , may be I am not as confident as DJ . They work and also you don't have to worry about re- quartering , the pins will reposition the wheel in the correct position .

[daveburrage]

Using roll pins to quarter wheels.

I've had a wheel locked with a roll pin shift on the axle. They are only a "C" profile and I suspect they will compress slightly. Once the wheel starts to move it will just get worse. I re-quartered and replaced with a solid pin and it has been Ok ever since.

regards

Dave Burrage

[ukjimoo]

Hi all

I thought it was about time i uploaded some more progress photos of our pair of 3Fs! Hope they are of interest.

Profiling the gland housing/slide bar mounting bracket on a rear cylinder cover using the rotary table.


Cylinder block and valve chest.


Cylinders between the frames and brake hanger brackets fitted. Chassis is starting to get VERY heavy now.


The coupling rods machined from solid. We produced 8 rods (for 2 locos) without a powered table feed! A lot of hard work but we were pleased with the result.


We have nearly completed the Crankshafts and are well on the way with the ConRods and Eccentrics. I will post some photos of these soon.

Jim

[ukjimoo]

Eccentric straps - These started off as slices of 3 1/2" round ph bronze bar.
They were faced, sawn in 2, mating faces machined and bolted together using capheads in counter bored holes. Then in the 4 jaw they were bored a good running fit on the eccentrics.


They were mounted on the rotary table on a specially made boss and then profiled.


This is the most challenging milling operation i have done so far in my time as a model engineer.

[Deleted]

Lovely work Jim, the way it looks in the picture you wouldn't guess that you found it challenging at all. Top rate mate...

Pete

[ukjimoo]

Thanks Pete

To have completed these without any disasters has been a real confidence booster!

Jim

[jgb7573]

Hi Jim,

They look good (and big). The only ones I've done have been for stationary engines and have been much smaller. I hit problems holding these in the four jaw as I managed to do the jaws up too tight. When I took the straps out of the chuck they went ping (well almost) and the bore was no longer round. I ended up remaking them from solid and clamping them to a sacrificial plate on the faceplate to bore them. Like you, I found milling the profile most satisfying.

John

[Smifffy]

Great work, keep the pictures coming.

Smifffy

[ukjimoo]

Here are some more photos showing the manufacture of the cylinders. These started off as slices of an 8" round bar! They were bandsawed and squared up on the mill. A friend of ours very kindly produced the bores for us on the faceplate of his large lathe as this was well beyond the capacity of the Boxford.

Milling the ports


Drilling the steam passages from the ports to the bores


Drilling the exhaust passages


Drilling for the valve spindle glands


On to the crank.....

An eccentric set up in the four jaw to produce the bore.
We decided to keyway these for the correct advance angle on the crank shaft as opposed to fine tuning them on the finished engine and locking with grubscrew and pin. The optimum angle was derived from a well known valve gear simulation PC program.
Of course if we get this wrong it will be a disaster but we have done it once before with success. Fingers crossed!


This is a 'dry run' of the crank with eccentrics before assembling the webs and journals with Loctite 648 onto the middle axle. These are to be pinned and the axle machined away between the webs.

Jim

[Deleted]

Very neat, and well presented.
JB