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Topic: Bike Chain Clock: how would you do it? (Read 1 time) previous topic - next topic

CowJam

Has anyone here made a bike chain clock likes this:
http://scienceblogs.com/sciencepunk/2010/09/bicycle_chain_clock.php

I like the look of it but the price tag is a little high.  How would you go about doing it?

fdufnews

#1
Sep 03, 2010, 12:53 pm Last Edit: Sep 03, 2010, 12:54 pm by fdufnews Reason: 1
Take any mechanical/electrical clock mechanism.
Remove the hour hand. Replace with some gear. The size of the gear gives the space between two digits on the chain. Multiply by 12 (or 24 if you want) this is the chain's length.
No need of an arduino to do that.

sciguy

#2
Sep 03, 2010, 01:07 pm Last Edit: Sep 03, 2010, 01:08 pm by amacmullen14 Reason: 1
What he said, but you probably want to put the wheel on the minute hand, and the distance on the chain between numbers is the circumference of the gear.  So every rotation of the minute hand, a new hour moves.

If the gear were on the hour hand, you would need the chain with no slack around the gear.
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CowJam

Ah, but the chain is going to be far heavier than your clock mechanism is designed to cope with.  I suspect a standard clock mechanism wouldn't move the chain.

I thought arduino (because I always do), RTC, stepper motor.  That then leaves you plenty of scope for making it do interesting stuff on the hour, etc.

sciguy

He could install some sort of support, could he not?
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CowJam

Could he?  I might have a go, I've got a spare clock mechanism.  It's used to moving very small bits of plastic though, I dont think it'll manage to move a chain even if it's supported.

Graynomad

#6
Sep 03, 2010, 02:50 pm Last Edit: Sep 03, 2010, 02:52 pm by graynomad Reason: 1
Yes the chain is heavier than clock hands but it's balanced, in a perfect world it would take hardly any energy at all to move, in the real world it will depend on the flexability of the links etc. but still be naf all I reckon.

The numbers aren't balanced because 12 will weigh more than 1 etc, but that could be adjusted if found necessary.
Rob Gray aka the GRAYnomad www.robgray.com

Kool-lites

How about using a stepper motor.  Won't be very energy efficient.

I got to get me one of those!

Osgeld

ditch the bike chain, use a chainsaw blade
http://arduino.cc/forum/index.php?action=unread;boards=2,3,4,5,67,6,7,8,9,10,11,66,12,13,15,14,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,86,87,89,1;ALL

darudude

#9
Sep 04, 2010, 03:27 pm Last Edit: Sep 04, 2010, 03:28 pm by darudude Reason: 1
@Graynomad: I feel like I'm missing something but why is this the case? Looking at the center of the gear in the picture of the clock linked to in the description, if the chain is balanced there will be no moment in the Z and Y direction (using right hand rule), but there will still be a huge one in the X direction correct? So in a perfect world, unless the gear box was designed so the moving gear was equally balanced by the gear box (i.e. was in the middle of a double gear box), there would always be a significant moment? And even if it was in the middle, there would be significant shear stress that would have to be taken into account?

Graynomad

Yes you're right, I was only thinking of the torque required to turn the chain, not any sheer effects or moments in the X direction caused inside the mechanism. With proper bearings on the main drive shaft that holds the cog this wouldn't be an issue unless the shaft broke/bent, but it's fair to assume that a clock mechaism wouldn't be constructed in that manner.

Makes you wonder then what he has done, stepper motor as mentioned or maybe the clock mechanism but isolate it from the load with a coupling and properly supported shaft and hope the startup doesn't strip the nylon gears.

I only wish I had the brass to ask $2338 for something like that.
Rob Gray aka the GRAYnomad www.robgray.com

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