Rewanui (1940 NZR in 1:64 and other distractions)

Lawrence Boul

Lawrence Boul

Western Thunderer
Yesterday's courier was exciting for 375's progress as the tyres arrived. Rather nice in stainless steel.
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My collaborator is quite fussy about these things, so the We needs #55 truck tyres and #65 on the drivers. The tyres do not have the step on the front edge so the centres will be smaller to suit - but visually the appearance will be correct (for a new tyre). In reality We375 will be modelled very much end of life, but worn tyres are not something I'm going to get into this time around!
Y7600-sml.jpg
 
Chris Veitch

Chris Veitch

Western Thunderer
I’m curious to know more about the ordering of the process, although the quality of the work is well beyond what I could achieve so please don’t take this as informed comment!

The casting must have been skimmed to diameter between the crankpin machining and the tyre fitting. How was it held (presumably on a mandrel?) and if you’re using split axles wouldn’t it be easier to fit the half axle first then machine it to diameter in a collet?

However it’s done, it’s splendid work on a very appealing prototype.
 
Lawrence Boul

Lawrence Boul

Western Thunderer
Chris Veitch said:
I’m curious to know more about the ordering of the process, although the quality of the work is well beyond what I could achieve so please don’t take this as informed comment!

The casting must have been skimmed to diameter between the crankpin machining and the tyre fitting. How was it held (presumably on a mandrel?) and if you’re using split axles wouldn’t it be easier to fit the half axle first then machine it to diameter in a collet?

However it’s done, it’s splendid work on a very appealing prototype.
Click to expand...
I'm feeling my way here a bit. It's the first time I've done an engine in 9mm, and while the process is familiar, none of my materials, products or tools seems to suit. Basically you are correct. It was held in a mandrel and yes my normal practice is to fit half axles first. I don't have a collet chuck (and if anyone has one for sale or can recommend for the Unimat 3 I'd be interested).

I'll post the mandrel at some point. I'm pretty happy with it, but another iteration is needed.

In 1:64 North Yard sell 3mm male/female half axles with an insulating bush. I've printed bushes that work just as well so I'm tempted to the same approach here as well, which is convenient to set up. But I need to make the half axles accurately. Or use the process Paul Berntsen described in MRJ to make the axles first and then fit everything up. Wheel bore is press fit, so I'd need to be careful with that or ream them out.
 
Chris Veitch

Chris Veitch

Western Thunderer
Lawrence Boul said:
I'm feeling my way here a bit. It's the first time I've done an engine in 9mm, and while the process is familiar, none of my materials, products or tools seems to suit. Basically you are correct. It was held in a mandrel and yes my normal practice is to fit half axles first. I don't have a collet chuck (and if anyone has one for sale or can recommend for the Unimat 3 I'd be interested).
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I have an ER25 collet chuck from (I think) ARC Eurotrade which has now closed down but I’d imagine that other similar Far Eastern clones are available - I don’t know what’s available in NZ but assume you have a similar selection of suppliers. It’s rather large and chunky for the Unimat but I got it because the ER25s were fairly cheap and I could also get chucks for my mini mill and Chinese 7x12 lathe. They work well in the mill but I’ve actually never used it on the 7x12. In hindsight I think an ER16 would be a far better choice for the Unimat, but again there are others here much better qualified than me to comment. That said, what I’ve got has served me fairly well and does the job for the relatively small number of tasks I’ve used it for so far.
 
simond

simond

Western Thunderer
Chris Veitch said:
I have an ER25 collet chuck from (I think) ARC Eurotrade which has now closed down but I’d imagine that other similar Far Eastern clones are available - I don’t know what’s available in NZ but assume you have a similar selection of suppliers. It’s rather large and chunky for the Unimat but I got it because the ER25s were fairly cheap and I could also get chucks for my mini mill and Chinese 7x12 lathe. They work well in the mill but I’ve actually never used it on the 7x12. In hindsight I think an ER16 would be a far better choice for the Unimat, but again there are others here much better qualified than me to comment. That said, what I’ve got has served me fairly well and does the job for the relatively small number of tasks I’ve used it for so far.
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Same here, ER25, and I think it was bought from Arc Eurotrade.

Apropos of nothing closely related, M14 x 1 is a standard spark plug thread and taps are easily available.

image.jpg

a 3D printer (FDM in this case) is a useful asset.
 
Lawrence Boul

Lawrence Boul

Western Thunderer
simond said:
Same here, ER25, and I think it was bought from Arc Eurotrade.

Apropos of nothing closely related, M14 x 1 is a standard spark plug thread and taps are easily available.

View attachment 269037

a 3D printer (FDM in this case) is a useful asset.
Click to expand...
Would be nice to find something similar. I would use it, and for the 5mm axles for the We it would be useful right now.
A tap would not be hard to get but such things tend to be expensive locally. I'm not averse to paying for my toys, but I like to be sure I'm going to play with them before shelling out - in the case of the M14x1 tap I've survived for 30+ years without. The printed threads seem to be working extremely well.
 
Overseer

Overseer

Western Thunderer
I bought a good ER16 collet chuck from Chronos UK quite a few years ago, I haven't seen them available recently but worth keeping an eye out for. As well as a good collet chuck you need to be careful to buy accurate collets. Cheap collets can be fine for holding milling cutters but may not be concentric enough for use on a lathe.
er16 collet chuck1.jpg
er16 collet chuck2.jpg

M14x1mm taps and dies are readily available from gunsmith suppliers at reasonable cost. It is apparently a common size for the barrel muzzle thread in European rifles.
 
Lawrence Boul

Lawrence Boul

Western Thunderer
Overseer said:
I bought a good ER16 collet chuck from Chronos UK quite a few years ago, I haven't seen them available recently but worth keeping an eye out for. As well as a good collet chuck you need to be careful to buy accurate collets. Cheap collets can be fine for holding milling cutters but may not be concentric enough for use on a lathe.
View attachment 269047
View attachment 269048

M14x1mm taps and dies are readily available from gunsmith suppliers at reasonable cost. It is apparently a common size for the barrel muzzle thread in European rifles.
Click to expand...
Spark plugs and silencers! Cartridge start?
 
Lawrence Boul

Lawrence Boul

Western Thunderer
Here's the wheel mandrel for turning the casting to OD.

The 3D printed mass of the thing has a printed M14x1 thread to suit the Unimat spindle. OD is 28mm or so.
There's also an M5 thread and recess in the front. Into this is fitted/loctited a suitably faced and threaded bit of 3/8" brass.
The whole assembly is then faced and the spigot reduced to suit the wheel bore (reamed 4.99mm). It's also tapped M3 to retain the casting. An M2 screw fitted to the crankpin bore acts as a dog.

This approach seems to work well. In my workshop something of this size is large. While the Unimat can handle it, it's not that much fun. Doing it this way is much easier and seems quite adequate. Now that the fixture is drawn I can print a small stock for similar tasks, or if something bespoke is needed I can draw and print that in a few hours.



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