MJEng Fowler A7 - what CAN'T I do on an ML7?

I understand the flywheel is 9" overall, which may just fit into the gap on my Myford.

The front and rear wheels at <9" won't fit. Do you know if they can be supplied pre-machined? I see they offer this for gears, but can't seem to establish if the wheels can be provided complete and no answer on the phone at present. I may be able to use a larger lathe at the local club but don't want to rely on access to it.

I understand there's the question of fly cutting the smokebox/etc. but I'm hoping this can be done with a boring bar in my mill.

The only other question I have is that I'm not sure about the final drive gear: Assuming <9" it might fit in the gap, but I think it might be pushing the limits of my Centec 2B which only has 9.5" z-axis travel...

Can anyone advise categorically on the above?

Many thanks,

William

The final drive gears can be cut horizontally:

Why do the wheels need to be machined? The hubs for my front and rear wheels were machined on the lathe, but the rims, T-rings and, during assembly, the wheels never went near a lathe. Front wheels:

Rear wheel:

Andrew

You have two options with the wheels.

1. Alan sells "finish cast" aluminium rims which need no machining. I went with these as option 2 was not available at the time. Most other designs that use cast wheels do need them machining eg Minnie and the Haining ploughing engines

2. He also sells rolled and welded steel rims, again these need no machining. I would go for this option now as the steel is a bit more forgiving of riviting forces

Flywheel and final drive gear diameters will fit the gap in the Myford bed and I'm 99% sure they are not too thick to fit.

I drilled the hole for the diff pinions with the drive gear held flat on the lathe cross slide, coming in from opposite sides and happy to say a silver steel rod passes nicely right through the reamed holes from one side to the other.

Boring head with the cutter sticking out the side hole is probably best for the chimney saddle and underside of the cylinder

Edited By JasonB on 22/11/2022 13:12:05

Edited By JasonB on 22/11/2022 13:14:21

That setup would be an interesting challenge on a Centec as you need to have a minimum distance of the radius of the gear between the column and cutter centre. It might be achievable by putting the cutter at the outboard end of the arbor, winding the Y-axis as far forward as it goes and having the rotary table overhanging the mill table.

To be in a comparable situation to the OP, you'd have to show us photos of something twice as big on your machines.

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To the OP: it is not so much the travel that the mill has, more the available daylight.

Make full size mock ups of the pieces to be machined in wood and come up with a setup that fits your machine.

If you have a vertical head on the Centec, it might be possible to cut the gear with the cutter rotation axis vertical and the rotary table also vertical, off to the side. Traverse through the cut with the Y-axis. That way, you need the gear's radius of daylight between cutter and table.

Following this through, if you tilt the head 45 degrees, you would only need roughly half the gear's radius of daylight, but lining things up and setting depth of cut would be very tricky.

Have a look through as much stuff as you can find on Deckel FP1 machines. There are lots of photos showing setups to mill what would at first sight seem impossibly big items for this class of machine.

Thank you - I don't have the drawings so I'm not sure what the full size dimensions of the flywheel and final drive gear are - presumably the latter can be supplied machined since MJENG can provide the entire gear-set machined so maybe less of a problem if it ends up being impossible on the Centec.

The 2B has 4" clearance from the centre of the VH axis to the column, I'll have to check how much from the horizontal axis centreline to the table at maximum extent.

I will have to measure up to calculate cutting the final drive gear in the flat as per Andrew's suggestion - it might be doable. 

Edited By William Ayerst on 22/11/2022 13:34:48

Both final drive and flywheel are 9" Finished OD.

I did all the machining of the gear castings and just got MJ to cut the actual teeth which works out cheaper than having them do it all. Alan now has Malcom Frost's gear cutting machine so can do individual gears if you can't manage the larger ones.

Final drive is 6DP so quite a cut for a smaller machine.

Thank you JasonB - I will ask him the same. I have posted on TractionTalk the same question though - i'm partway through a 5" locomotive build which i'm enjoying greatly, but starting to realise that I may not be the kind of person to go to a club track to run it - so I'm thinking of building something I can in theory run anywhere - even if at slightly more of a sedate pace.

I'm just not sure what I can expect to do with/on a 2" Fowler A7 / A7 Compound when/if it's complete!

Silly question - if I have to potentially outsource the final drive and flywheel (Alan? at MJEngineering suggested a 10" OD) - could I build a 3" instead other than the additional cost of materials? Or is that just too much for those machines?

Edited By William Ayerst on 22/11/2022 16:49:07

I have asked a mod to delete the offending post.

Andrew

On Tarmac a 2" Fowler will pull two adults quite happily, the larger engines are more at home on a rutted rally field.

Don't know what Alan is looking at but the drawings clearly show 9" dia as I said so still room to swing the rough casting at least as far as diameter.

And there was me thinking that Andrews 4" engine was approx twice the size of a 2" Fowler. If that's not showing something twice the size I don't know what is.

Slightly OT I'm afraid, but how did make the T-rings Andrew?

I am building the 2" Fowler road locomotive using a Myford 7 and a Tom Senior mill

The wheel rims do not need any machining. Only the final gear and the fly wheel were too big. I machined the final gear in at work and cut the teeth at home on the mill. The fly wheel I did in a rush at work an I am not too happy with it. No more access to work machine any more but it will sort out.

The diff was machined out of iron disks from M-Machine wounderfull service at all times.

All the gear cutters came from Ebay.

Go for it, the problems have a way of sorting themselves out as the build progresses

Dave

Dave, was it the combined thickness of faceplate and flywheel rim that meant it would not fir in the gap ?

Hi William,

An option when building the A7 Fowler, if parts will not fit on your Myford is to have it done elsewhere. Join a local model club. Fellow members may be able to help or get a commercial shop to machine the parts.

I built a 6" Ruston Proctor traction engine with the majority of the turning done on a 9" Southbend lathe (4 1/2" swing) The rear wheels are 24" diameter and my lathe was big enough to turn the hubs, shafts, etc. The wheel rims were rolled from flat bar and spokes laser cut. The only turning that was required after fabricating the wheels was to true-up the ring on the inside of the wheel where the park brake rubs. The wheel rims, although a millimeter or 2 out of round were not turned and have rubber bonded to them.

Most of the machining work was done on a Sieg SX3 mill and not on a lathe. Castings and gears purchased from Live Steam Models.

(Build about 1,500 hours over 7 years) **LINK**

Edited By Paul Lousick on 22/11/2022 22:27:55

I designed and built my own bending rolls to form the rims, and the plan had been to add a couple of grooves to roll flat bar the 'wrong' way for the T-rings:

For reasons I can't remember I decided against this and bought laser cut quadrants for the T-rings. These quadrants were then arc welded together to form rings. Once rolled the rims were arc welded, and then the T-rings welded in place. I used a fixture to ensure that the T-rings were welded in the correct place, completed T-ring in the background:

The T-rings were an easy push fit in the front rims after welding so my calculations were correct. On the back wheels I had to remove about 15 thou from the rings as I had forgotten that the hot rolled steel used for the rear rims is not accurately sized.

It was a lot of work welding the quadrants together, and the laser cut quadrants were not cheap, so in retrospect it might have been easier to roll the rings as initially planned.

Andrew

The originals would have been rolled from "T" section but I have only seen this done on one model.

Most are done like Andrew shows with a hoop rolled as one or sometimes two which are trimmed to avoid an unrolled end and then welded. Smaller engines can have the webs cut as "washers" but it is less wasteful of material on larger engines is part circles are nested closer together.

One other option is to mill some through slots into the rim material before rolling and then cut your webs with matching tabs to go into these. You then puddle weld them from the outside which puts less heat into the assembly and you don't risk getting a concave face to the rim. Again not seen this done very often.

Edited By JasonB on 23/11/2022 07:31:19

The combined width of the face plate, and casting, and mounting bolts just would not fit. Not even near.

Dave

Thanks Dave, thought the diameter would be OK but was not 100% sure about stick out

Thanks Andrew, I'm looking at a smaller scale than you, so making a special bending roller wouldn't be a huge investment in effort and materials (I have a set of 'normal' bending rolls that I made years ago but it would probably be easier to make a new special than modify them).

On the other hand, I like Jason's suggestion of the tabbed webs - decisions, decisions...