MJEng Fowler A7 – what CAN’T I do on an ML7?

[William AyerstParticipant @williamayerst55662]

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

[William AyerstParticipant @williamayerst55662]

[Anonymous]

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

[JasonBModerator @jasonb]

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

[DC31kParticipant @dc31k]

Posted by Andrew Johnston on 22/11/2022 13:03:05:

The final drive gears can be cut horizontally:

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.

—

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.

[William AyerstParticipant @williamayerst55662]

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

[JasonBModerator @jasonb]

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.

[William AyerstParticipant @williamayerst55662]

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!

[William AyerstParticipant @williamayerst55662]

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

[Anonymous]

Posted by DC31k on 22/11/2022 13:28:25:

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

I have asked a mod to delete the offending post.

Andrew

[JasonBModerator @jasonb]

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.

[JasonBModerator @jasonb]

Posted by DC31k on 22/11/2022 13:28:25:

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

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.

[Andy StopfordParticipant @andystopford50521]

Posted by Andrew Johnston on 22/11/2022 13:03:05:

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.

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

[Dave Shield 1Participant @daveshield1]

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

[JasonBModerator @jasonb]

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

[Paul LousickParticipant @paullousick59116]

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

[Anonymous]

Posted by Andy Stopford on 22/11/2022 20:14:50:

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

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

[JasonBModerator @jasonb]

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

[Dave Shield 1Participant @daveshield1]

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

Dave

[JasonBModerator @jasonb]

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

[Andy StopfordParticipant @andystopford50521]

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…

[William AyerstParticipant @williamayerst55662]

Having spoken to Alan at MJ Eng, and Tim Watson, and a few chaps on the TT forum – it seems that maybe I should really consider a 3" engine – in that the items which are too big for the ML7 and Centec for a 3"-scale are the same items which are too big in 2" scale, so not net difference in that aspect? Or am I oversimplifying things?

[JasonBModerator @jasonb]

You may find a few more of the 3" parts that could be tight on the Myford such as brake drum, winding drum, 3rd shaft gear and the cylinder will also be quite a lump so allow for more parts needing larger machines plus the long term how will you transport the engine and some form of driving cart.

If Fred on TT chips in he made a very nice 3" on a myford and warco mill and borrowed a friends machines for the larger items

Edited By JasonB on 24/11/2022 10:11:24

[SillyOldDufferModerator @sillyoldduffer]

Posted by William Ayerst on 24/11/2022 08:08:47:

…it seems that maybe I should really consider a 3" engine – in that the items which are too big for the ML7 and Centec for a 3"-scale are the same items which are too big in 2" scale, so not net difference in that aspect? Or am I oversimplifying things?

Just an observation as I've never built a traction engine but, it's straightforward to make components that fit on the lathe and mill, and straightforward when a component far too big – then you have to have it machined by someone else, £commercially, or by making friends at a club. It's the middle ground that gets exciting because an experienced and imaginative machinist can often get tight-squeeze jobs done with ingenious set-ups. This opens the door to different answers.

• Person A with basic skills looks at the plans, and realises that some parts are too big, therefore the job can't be done.
• Person B with advanced skills and is familiar with that type of build, identifies the difficult parts, and has a clever experienced think about ways and means. This chap might well be able to do a job too difficult for Person A!

In the past people achieved remarkable things with Myford lathes because they had to. But it took time and and thought. I'd describe myself as being Person A who is slowly and painfully learning to become Person B. On the plus side, I have semi-relevant work experience, an interest in the history of engineering, an extensive library and much help from the forum. Not so good, I'm self-taught. In consequence, my machining skills are full of odd gaps and I make a lot of avoidable mistakes! Theory is very helpful, but it doesn't provide hands-on skills. To get them, it's necessary to cut metal, thus discovering and extending the limits of the machine and the operator. Practice!

The best way to become Person B is moot. I prefer to start small and methodically extend my skills by tackling more complex work in a series of small steps, a sort of self-imposed apprenticeship. Others are motivated by challenges, bigger the better, and learn best by jumping straight in at the deep end. Trouble with the latter approach, is it has a high failure rate: the second-hand market is littered with part-built locomotives, and it was once joked that most workshops had a half finished Quorn under the bench. The problem is these things take thousands of man hours, and take even longer if a learner has to feel his demoralised way at every step.

If it were me, I'd take the uncertainty about 2" versus 3" traction builds as a warning that I might be out of my depth. I wouldn't mind 'wasting' a year building something smaller just to gain experience. Against that, note Dave Shield's answer, and his comment 'Go for it, the problems have a way of sorting themselves out as the build progresses'. He's right, but I suspect Dave is more experienced than me. Noting that most jobs are much easier when you know what you're doing, I'm less confident because I know I have gaps!

Dave

[BazyleParticipant @bazyle]

Don't forget the finished model is going to get heavier by the cube of the dimension and assemblies you can lift on a small one cause a slipped disc on the bigger one, Also bits dropped on your foot do more damage.

Meanwhile Fred's model above looks superb. Another item on my wish list.

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