Anatomy of a drum spinner

[Danny B]

So after a great time at Manchester (thanks for all the positive reception Road Bump received!), and spending a bit of time talking to Jamie McHarg at the event, I think the time has come where I'm ready to build a spinner.

My plan is to go for a drum spinner, approximately 100mm diameter by 150-200mm width. I have already bought what I feel is a suitable motor: https://hobbyking.com/en_us/turnigy-...___store=en_us

The main area I'm struggling to work out myself is what goes into a suitable mounting system. Basic stuff I could really do with some pointers on:

• Shaft material and diameter
• Bearings/bushings
• Pulley ratios
• What style of drum is easiest to make for someone with limited resources and connections?

Any help would be hugely appreciated!

[team death]

I wondered who's the Road block featherweight replica belonged to-
I was thinking of building a replica of piece de resistance feather-
maybe we could have a replicas event, I know theres a beheamoth
somewhere too

[Maxamuslead]

although i have not built a spinner at all i could help answer a few things.

Shaft material. high grade Alu (7075) Or Titanium

Bearings are better (less rolling resistance = More RPMs = More KE) but more complex ( correct bearing, preloading etc)

Bushing cheaper and simpler but higher rolling resistance.

I would suggest reading 360 build log, Team Eventorizon build log. Really any spinner build log

[typhoon_driver]

For a drum spinner, a fixed shaft is generally the better option as it aids the structure of the machine better than a rotating shaft.

For materials, I'd look at silver steel. around 20 to 25mm dia should be a good starting point. Titanium is another viable option. I wouldn't recommend aluminium.

Both bearings and bushings are viable options and have been used successfully. Bearings are a little more forgiving if things aren't quite 100% accurate.

Ratios are entirely dependent on what speed you want to achieve.

What tooling do you have available to you?

[Danny B]

Ratios are entirely dependent on what speed you want to achieve.

What tooling do you have available to you?

I'm not sure what speed would be considered adequate for a drum, but the lowest I dare gear it is 1.8:1, any less reduction than that and I'm worried there won't be enough torque. Assuming mechanical and aerodynamic drag knocks 20% off the output speed, that ratio should be good for around 11,800rpm and a tip speed of 150-160 mph.

I personally only have access to hand tools at this point, and I don't really know much about CAD software. I did ask around a few local CNC places, but none of them were very interested in doing one-off parts. If anyone here knows anyone who can help on this sort of thing, it would be enormously appreciated.

[Eidg]

I normally use tappered roller bearings.