TOPIC:

The new 35 & 15 T gears arrived yesterday... there's really not a lot of meat on them

The best I can come up with so far is to take a little of the height off the boss of the larger gear, glue/press the boss of the small gear into that, bore the centre out to 5mm, then make spacers to control the sideways position in the gearbox.

eddrick wrote:

Cool Jonny! There'll be no stopping you with what you can make soon!
No critisism over the lathe here, the Unimat is supposed to be really good for what it is, & should be more than capable of hacking up plastic & ally for toy car bits! When it turns up, let me know what the story is with the tailstock & maybe between us we could come up with a chuck for it.

I could've sworn the final gear was identical to the SRB... I wonder what it was I hacked up for my XR311 then...

Best option for joining gears together is to bore a hole in the larger gear, machine a "nose" on the smaller one that is say 0.05mm larger than your hole, then press them together. For maximum non-fall-aparty-ness, drill & tap (Say M2) at the interface & threadlock a pair of grubscrews in. Or weld it, or CA glue it.

Motor plates - I drew up both 380 & 540, but can't for the life of me remember what topic I posted them on - do you want them emailing?

Thanks eddrick - I seem to have ended up with two original Holiday Buggys & two Sand Rovers (as well as a re-re of each, I'm not quite sure how that happened ), IIRC one of each has the 380 setup & the others are 540's, so I don't really need any motor fittings

Re the tailstock, looking at the Unimat manual (which the thing is a clone of), + the photos it looks like the tailstock "should" be assembled with a 3.5mm collet, collar & pin spike ... but I can't see any reason why I couldn't put any one of the other different size collets in there (1, 2, 2.5, 3, 3.5, 4, 5 & 6mm) & an appropriate size drill bit in it ... this seems so obvious to me I don't know why it's not shown as a feature

Other option is to get a chuck with a plain spindle, & use your tailstock collet chuck to grip that spindle. - I'm actually looking at something similar for my mill, & have to warn you that so far I haven't managed to find a tiddly keyless chuck that ISN'T absolute cowpat! I'm currently looking into how good the Proxxon keyless chuck is, with a view to making a spindle to suit it (They come as just the chuck, without spindle), then I'll move on to looking at the Dremel version.
Collet chucks are ok, but they've only got a limited gripping range for a given size (Usually).

Thinking about the motor bracket, er, didn't you supply me with the details to draw it?

Yes, the SRB final gear is 0.6m (As is the spur/pinion), so that must be what I hacked up for the XR311! (Used spurs on my F2)

The distance between centres is pretty small (I'm guessing about 125mm) ... I'd like to stock up on cutting tools & nylon bar too, but I think I'll wait for the thing to turn up - according to Hobbyking, airmail will take 7 to 45 (! ) days

Directplastics online for plastic bar (They deal with privateers)
rdgtools.co.uk for small tooling, chronos engineering are helpful too.
If you're just gonna be chopping up fairly soft stuff, high speed steel is fine - comes in cheap bars, will happily do up to mild steel & is easy to grind to the tool shape you want with a normal bench grinder.
Brazed carbide tipped tools are also really cheap & should last forever on soft stuff, (Will do stainless ok) but they're difficult to re-grind when dull.
Don't bother with indexible carbide tooling, you're unlikely to ever need it (Will do really hard stuff) & tips are expensive.
Might be worth looking at RDG's brazed carbide lathe tool sets, I think they do one small enough for Unimat - check the distance from the bottom of your toolholder to centreline of chuck, this is the maximum tool height/thickness you can have without a lot of grinding back. Lees than is ok, you just put beercan packers under the tool to get the centre height right

Thanks eddrick - even if websites where you have to register & fill your basket up before they'll tell you what the postage will be really wind me up ...

I was leaning towards Nylon 6-6, but seeing that prices for Nylon 6 are about 25% lower, I'm wondering if the lower melt point is really a problem ... I mean, if anything is getting to 200 degrees C, then I'm in trouble anyway

What are you doing with nylon? Would a different material be better anyway? (Nylon can be a pig to machine & get a good finish)

Spotted a used set of gears on eBay:

Another (cleaner) set from the same seller:

It'll be interesting to see what they go for, there can't be many good sets left