Missing mechanical specs for DIY projects

I’m a retired electronics design engineer building RC aircraft and am designing a launch trolley. I need 4 wheels. Do you have them? If so, what axle diameters? Do you have axles to suit?

I then need a powered rear axle. A simple brush motor is fine. Shaft diameter? I’ll need two chain sprockets if I’m using chain drive - one for the motor, one for the rear axle. AND DIY chains for them. Do you have suitable components? Otherwise a right-angle pinion drive using two spur gears. Do you have them to suit the axles and the motor?

At the front I’ll need a standard parallel link steering setup. Same questions, but more of them.

In my boyhood I built heaps of stuff like this using Meccano and Ezy-Built. Seems simple and obvious to me. Why isn’t this stuff still listed and available?

Not trying to be nasty - just in a hurry and frustrated at what seems to be a complete lack of obvious info - unless you only buy over-the-counter stuff - but then I thought you guys were into the “Maker Revolution”.

Hey Carl,

Here are some good places to start so you can start form a shape/direction for your project (these are parent category links, you should click on the “view all” link on each category to explore in more detail):

For structural gear, take a look at Makeblock products. Search “Makeblock beam” or “Makeblock shaft”. We haven’t categorised them very well yet, but they will most certainly be discoverable by search and suit your needs.

There is no such thing as a free lunch with bespoke mechatronics projects - it’ll take some diving and exploration if you’re not familiar with what parts are accessible these-days.

Thanks for the prompt reply, and the links. What annoys me is that we seems to be reinventing the wheel - mech specs, and most particularly standards, should pretty much be set in concrete by now, yet, the shaft diams I see are all over the place, as just one example.

I realize that, as an Ozn, you’re at the mercy of the Chinese manufacturers, and those guys don’t even know what a cutting facet on a drill bit is, to judge by what I’ve bought.

I also acknowledge that you’re a commercial organization, and customer education can’t be more than a side issue, but there’s a heap of work needs doing here with the younger generation.


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I hear you! Hardware is a fast moving market in the maker realm and is tough to lock down (in a reasonable way). Often it’s best to know what’s accessible and work backwards from there.

Tamiya 70100 Track and Wheel Set: relevant but inappropriate.
Metal ball casters: Completely irrelevant.
Skate Wheel: Completely irrelevant.

ALL stainless steel!!! Have you EVER tried to work stainless steel, other than in your dreams?

Mounts & Hubs:
The less said. the better.

Sigh! Looks like it’s back to Aliexpress, Gearbest and Banggood. At least, eventually, I get what I need, and at a decent price.

When I click on the “View all Products in Wheels” link, I am taken here

I can see in general wheels, it’s getting closer to what you need. Clicking on the view all link for that category takes me here

Where I see products such as POLOLU-1420 which we’ve used for our own “just for fun” launcher in the past for what sounds like a similar project.

Similar user experience for the other cats. I could get a “build in mind” within two minutes of clicking around.

Worth mentioning as well @Carl13454, if you build a project you can share it here

Include the details of the build, a wishlist of parts, and in the event someone has a similar need in the future, you/us/others can share your project with them.

Better still, you get paid for sharing it.

what sounds like a similar project

Polulu wheels are 60x8mm and look … well, kindly, toy-like. I’m looking for solid 80x20 with thick rubber treads - 80x30 to carry the load, with at least 3mm steel axles. Maybe vaguely similar, but nothing like my intended trolley.

I could get a ‘build in mind’ within two minutes of clicking around.

Not sure what a “build in mind” is. I’m presently building this IN my mind, but eventually it’s GOT TO WORK in physical reality.

And the chain drive or pinion gears for the rear end?

can share your project with them.

Well, I’d be happy to if it were of use to them. But this is ONLY of interest to someone who’s building an experimental aircraft, can’t be bothered with wheels or U/C, needs to get it off the ground safely and reliably, and is the only person present.

Normally, you toss a model aircraft into the air if you don’t want a ground take-off. But if you’re holding the transmitter and not sure just how it’ll behave, it’s much better just to sit it in a fast trolley, run it down the strip a few times until the trim is OK, then let it go!

Got an Arduino Nano taking care of the trolley - stops it, turns it around, and trundles back home afterwards. It’s only the mechs that are now a confounded nuisance.

Sounds like a serious upgrade to our launcher! I hope the build goes well Carl, and please do keep us posted!

Hi Graham

I hope the build goes well Carl, and please do keep us posted!

Thanks for the interest. This looks promising:


… and getting closer:


Given away the steering - too much hassle. Instead, powered rear axle,
single caster nose-wheel, and - the coup de grace - a long length of
fishing line with a motor-powered take-up reel to wind the thing back
in. NOT elegant, but much more do-able.

And might toss the Nano in favour of a pair of soon-to-arrive ESP32s to
Bluetooth link the plane throttle with the trolley throttle.

Looking much easier, but probably still too specific for your
readership. Probably near year-end, so I’ll post something before I
crash it.


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Sounds like there is momentum building, thanks for the update Carl!

Keep us posted with how you go - no such thing as too specific!