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Member postings for Martin Rock-Evans

Here is a list of all the postings Martin Rock-Evans has made in our forums. Click on a thread name to jump to the thread.

Thread: Is Model Engineering "green"?
29/11/2021 10:19:57

I find it a really interesting topic. In comparison to other hobbies like motor racing or flying, we're probably not too bad.

Some of our impacts maybe fairly obvious (heating the workshop). What about the impact of some of the chemicals we use for cleaning, finishing, etc? Do we consider the environmental implications when choosing process a) over process b)? What should we be avoiding?

Thread: Electric vehicles
18/11/2020 22:23:38

Not just overhead wires, but wireless car charging road trials as well: **LINK**

I have no idea if either of these ideas will go anywhere, but neither did we really know how the motor car with IC engines would take off when they were first introduced. Less than a decade after the first few IC motor cars and the world had changed. The point is that although electric cars and the national infrastructure have limitations now, things will change. We just don't know what the answers will be, so lets be part of the solution trying to find the answers.

Thread: Virtual Meet Ups
17/10/2020 10:30:02

Hi Neil, I too would like to listen in please, but will need to be a silent observer.


Thread: High Temperature Air Source Heat Pumps for Domestic Heating
08/10/2020 20:17:43

We had an air source head pump installed last year that works well with our underfloor heating system. Here in the South West (Mid Devon), the ambient air is sufficient that it rarely showed any ice last winter, so COP has been good. Much of the power is from our Solar PV panels, so free electricity leads to free heating, but we did need to be careful to set the thermostats sufficiently low out of daylight hours to prevent excessive bills from nighttime heating.

One thing we considered was keeping our old oil fired boiler alongside the new ASHP, to provide heat in freezing weather, however if you do, the RHI will have to be metered. However, the RHI is still capped with the same maximum annual RHI being based on your ECP rating if you have a meter or not, so in terms of maximising the RHI, we opted to completely replace the heating system and have the RHI unmetered.

Another thing to consider is the actual design of the system and location of ancillary equipment. Although our ASHP is almost silent, the heating circulation pump is not (same in any large central heating system) and with our new heating layout system, the circulation pump was installed in our airing cupboard, just outside our bedroom. This is sufficiently noisy to wake me earlier than I'd otherwise want...

Thread: Will this cutter be ok for my Tom Senior light.
03/10/2020 07:56:25

It must take ages each time they need to replace or turn the inserts!

Thread: Boiler studs through or blind
27/08/2020 15:23:31

I'm building a 3" Burrell Traction Engine and have a commercial copper boiler. It has come time to fit the cylinder to the boiler. The drawings call for 24 2BA copper studs, but I can't workout if the tapped holes in the boiler for the studs should be through holes, or blind.

The boiler is 1/8", with a second 1/8" pad silver soldered onto the inside where the cylinder sits (so there's 1/4" of copper to bolt to). The studs are radial (so need to be inserted after placing the cylinder and can't be soldered in place). A through hole would give 7-8 threads. However, if I go for a blind hole, I'm not sure I'd get more than 3 threads (and I'd be worried about ensuring the holes are exactly the right depth). What would be the normal practice?

Many thanks in advance,


Thread: 20 degrees vs 14.5 degrees pressure angle for gears
27/08/2020 15:06:58

Stephen, I'm not sure if this will help now as it's been best part of a month, but when I made the gears, I pretty much just followed the drawings. There's plenty of space for the large boss (you can just about make it out in the photos below).

The only thing I remember not being quite right on the drawings was that the dimension for the shoulder on the small gear didn't match up with the bore of the large gear, so I just ensured that they matched so that when the larger gear was bolted to the smaller one, it would fit on the shoulder and ensure that the gears are concentric.

2020-08-27 14.46.04.jpg

2020-08-27 14.47.24.jpg

Thread: Coping with deafness
03/08/2020 16:28:56

I'm kinda surprised that no one has suggested a good old fashioned bell-pull. Linked by a set of cables or rods from the pull by the door to a bell in her main room, she may not be able to hear the bell, but wouldn't she see it moving? The same pull could be linked to bells in multiple rooms. With sufficient imagination, this should be relatively easily achieved.

Thread: 20 degrees vs 14.5 degrees pressure angle for gears
14/07/2020 14:16:37

Stephen, yes, I used the full set of castings from Bridport for the drive gear chain.

Thread: fusion 360 cam
27/06/2020 13:00:40

I can't claim to be an expert, but something that has tripped me up in the past is that if the stock in F360 is set to the finished height, it won't want to machine the top surface. Maybe try setting the stock size a little higher?

Thread: Enamel Paint
01/05/2020 22:18:42

Hi Stephen, maybe try Phoenix Paints **LINK**? They have a number of different enamels in 50, 125, 250ml tins. (that said, I've not used them yet, just seen them advertised and recommended in Chris Vine's book on painting locomotives)

Edited By Martin Rock-Evans on 01/05/2020 22:21:28

Thread: Telescopic bore gauges.
30/04/2020 18:03:24

Just a thought on getting practice measuring a bore, someone much wizer than me suggested practicing with a known bore such as the bore of a ball bearing. these tend to be hard and fairly accurately ground to a size, with published limits. Much cheaper than a standard, available in a range of sizes and probably good enough for beginners

Edited By Martin Rock-Evans on 30/04/2020 18:04:13

Thread: Horn plates bowed when adding rivets
28/02/2020 20:47:11

Thanks for all your thoughts. As Dave W suggested, I've tried pressing the bend out and that has worked surprising well! One main press across the double row removed most of the bow, and then I did the same again in a few more places and it's now as flat as I can hope for. Nothing more than a gnat's hair under the straight edge now.

2020-02-28 20.31.15.jpg

I'll take your suggestion Jason for the second plate and hopefully that one will remain flat without needing to resort to brute force.

Thanks for the complement Andrew. I should admit to carefully chosen photos, because there were certainly a couple of rivets drilled out and re-done when the rivet snap moved and left a nasty dent across the centre of a few otherwise nice round heads!

28/02/2020 19:06:36

I’m in the process of making the horn plates for my 3” traction engine. All was going well before I started to add the decorative round head rivets around where the boiler would be riveted up in the full-scale engine. The bearings, crank shaft, spectacle plates, etc all fitted and ran well and I’m fairly sure the plates remained flat after I’d drilled and countersunk the holes for the rivets because the other plate I haven’t riveted yet has the countersunk holes ready, and is still flat.

However, when I added the decorative rivets, the once flat horn plate has now a pronounced 1/8” bow in it away from the rivet heads (convex on the inside of the plate), mostly from the double line of rivets across the middle of the plate.

2020-02-28 18.30.00.jpg

On the outside, the rivets look good, it's just that the plate is now bowed.

2020-02-28 18.28.13.jpg

When installing the rivets, the plate was drilled and then countersunk on the inside. Each round head rivet was then inserted into the hole, the head placed on a rivet snap and the inside was riveted over until flat and filling the countersink.

2020-02-28 18.36.00.jpg

2020-02-28 18.36.35.jpg

My questions are:

  1. Why would adding decorative rivets cause the plate to bow like this
  2. What might be the best suggestions for correcting the bow
  3. How to I prevent the other plate bowing in the same way

Any suggestions and ideas would be truly welcome.

Many thanks


Thread: 20 degrees vs 14.5 degrees pressure angle for gears
06/12/2019 18:28:32

I brought myself a 24" length of 1" precision ground EN1A from College Engineering Supply. I guess it is a little expensive, but on the other hand, in comparison to other parts it's not too much, and I knew it would fit well when the bearings were reamed. I didn't put bronze bushes into the hubs, so they are cast iron on the steel shaft, but I do have bronze bushes in the final drive tube, mostly because that was fairly easy to do with the castings I have from Bridport Foundry.

Thread: Issue 286 Spot drills
30/09/2019 18:46:07

Interesting article Ian. However, I'm struggling slightly to see why the small angle spot drill is bad because it must have a similar effect to a centre drill or pilot hole in that the first contact will not be the centre of the drill?

Thread: 20 degrees vs 14.5 degrees pressure angle for gears
29/09/2019 17:51:37

Hi Stephen, I went for the specified 20 deg PA in the end. Steve Holder at was able to supply the cutters I needed second hand at a reasonable price.

Here are some of the resulting gears:20190521_101833.jpg

2019-09-02 10.56.07.jpgHi Stephen, I went for the specified 20 deg PA in the end. Steve Holder at was able to supply the cutters I needed second hand at a reasonable price. Here are some of the resulting gears:2019-07-14 19.31.31.jpg20190521_101833.jpg

Thread: What hand protection do you use?
01/08/2019 17:04:32

The wonders of the internet supplies almost everything that I need (want?). The only problem is working out what I need, and funding it.

In this case, ebay came up with


01/08/2019 13:15:06

Following on from the thread about deburring, I was wondering what hand protection people tend to use in their workshops?

I've been using Rath's PR88 cream for general protection from oil and dirt having given up on latex gloves as they would split/tear on sharp edges, but do people use tougher gloves?

Thread: What Did You Do Today 2019
21/05/2019 22:04:05

Today I cut the final tooth on the final drive gear of my 3" Burrell.


I was really chuffed when it fitted with the drive pinion, right up until when I tried to turn it all the way around and found one tooth that didn't fit! Turns out I missed one on the final pass.


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