While awaiting the opportunity to make a start on cutting the gears. In spare moments, I have been having a play with the Gear Generator add in, in Fusion 360.

I decided to create myself a working drawing of the Shogun gear replacements that I need and I was quite pleased that Fusion came to the same conclusions about size etc. that helpful fellow modellers (who are far more experienced in the subject than I,) had already worked out.

A friend and fellow Guild member fell soft and offered to have a go at 3D printing my 29 hole division plate.

It turned out really well with all the indexing holes fitting perfectly and the main bore just requiring a little scraping with a 3 cornered scraper to enable it to ease onto the shaft.

Had I been quicker on the uptake I might have added the numbers to the STL file before sending it but it only occurred as I was fitting it to the Spin indexer.

For those that don’t know what a Spin Indexer is, this is mine fitted with the 29 hole division plate.

The eagle eyed will note that the label says ‘5C’ 5C is the type of collet what these indexers come equipped to accept as standard. I don’t have any 5C collets nor am I likely to make use of any so when I saw the Spin Indexer offered at a discount price already fitted with a 5C to ER32 collet adapter I decided that I could make wider use of ER32 collets so I bought the indexer and a set of ER32 collets. Since then, I have added an ER32 collet chuck for my lathe so now I can use the ER32 collets in both the lathe and spin indexer alongside my more often used ER25 collets

This means that I am now set up to have a go at cutting the 2 x 29 tooth gears that I need for the Shogun gearboxes. I am still doing carer duties and Chris doesn’t have her stitches out until next Wednesday. So it will probably be later next week before I take the plunge and have a go.

Discussion over on my gear cutting thread on Western Thunder has had input from several members who are experienced in cutting their own gears and part of the discussion was around worm and wheel gear sets. 

We discussed that it is possible to use a length of say M6 x 1.00 threaded stud to make the worm and use an M6 x 1.00 tap in the lathe chuck to cut a wheel with at least one member having done this in the past. having seen this done in a video sometime ago it was of interest. Then I used a thread gauge to check a Roxey Mouldings Worm and Wheel gear set which came with one of their fold up gearboxes. The metric 1.25 thread gauge fits perfectly but the diameter of the worm is 6.3mm so I think that it’s actually more likely to be 1/4″ x 20TPI rather than M6 x 1.25

We also discussed that using a BA profile of 47.5 degrees would be better than using the standard 60 degree of a metric or US imperial thread. Having checked my BA thread chart I was a little surprised to find that 0BA is 6mm and has a 1.0mm thread pitch. The key difference between Oba and M6 is the angle of the teeth being 47.5 as opposed to 60 degrees. I have lots of 6mm bar recovered from scrap printers and toner cartridges so some trials are in order.

I have been asked if I will do a ‘gear cutting 101’ for those with little understanding of gearsand gear cutting (I count myself amongst them… ) So I will endeavour to share what I have determined so far.

Gear sizes/measurements come in two flavours (as you might expect) Imperial and Metric. The descriptions for these are:

Involute DP Gear Cutters ( DP standing for Diametral Pitch inch size) These come in two pressure angles 14.5 degrees and 20 degrees

Metric Module (MOD) have a declared pressure angle of 20 degrees.

Each Involute DP or Module set is made up of 8 cutters which perversely, the number for each type is reversed from each other

Having determined with help that the missing final drive gears were MOD 0.3 and that MOD 0.3 is a bit fine for 7mm models I bought from Chronosa set of MOD 0.5 gear cutters.

I also bought a single MOD 0.3 No5 cutter which will cut 26-34 teeth from a company in Japan called Gavan Tools but no great surprise that once despatched and I started tracking it, it was coming direct from Shanghai China. That said, the tracking information provided was excellent and it arrived safe and sound.

This is the same image with a little more contrast to all you to better read the details

In my last post I mentioned that a fellow Guild member had a couple of new boxed examples off the Shogun units. He kindly shared some photos of them which with his permission I will share here so that you can see what we are aiming for in the end.

This is the accompanying data sheet

You will note the bit about a ‘special’ axle. I checked mine and the bushes are under the standard 3/16 axles that we traditionally use so I plan to drill and ream mine out to 3/16 making the drive gear to suit.

At Guildex (Stafford) I bought a couple of Tower Models 7mm O Gauge ‘Tower Power’ Shogun 5-Pole Canon Motor w/ Multi-stage Gearboxes. Although I didn’t know that’s what they were at the time, the price was right but I did note that they were each missing their final drive gear. In my view, the Canon Motors and fly wheels alone were worth the £25 each that I paid for them.

Enquiries on Western Thunder and the GOG forums, identified the product as described above and subsequently contacting Tower Models confirmed that there are no spares available.

One member of both forums happened to have a couple of the same gearbox units new and boxed he was very helpful in confirming that the gearboxes or at least his boxes were 25:1 ratio he also counted the number of teeth and confirmed that there were 29.
From further discussion it also revealed that San Cheng who produced them for Tower also used the same gearbox side frames for an 18:1 version of the gearbox using slightly different idler gears.

We ultimately came to the conclusion that the final drive gears are 29 tooth the Module is 0.3 and the diameter of the gear is 9.26mm