Tortoise Auxiliary Switches

Discuss the prototype and how to model it.
andrew jukes
Posts: 211
Joined: Thu Mar 05, 2009 4:15 pm

Re: Tortoise Auxiliary Switches

Postby andrew jukes » Thu Sep 10, 2009 10:41 pm

How not to develop a product!

I did finally get a batch of replacement pcbs made and have upgraded 8 Tortoises so far. What I'm doing is swapping the pcb (which takes a very few minutes), securing the wipers to their arm with one 12BA nut and bolt on each and bending the wipers so they are all of a similar shape and pressure.

An interesting discovery is that one of my Tortoises is clearly Circuitron's second attempt to get the pcb right (Rev B being their third). The pcb is labelled just 'Rev' and is as poorly aligned as Rev B but in the opposite direction. Goodness knows what their first attempt was like.......

Something else to be unhappy about in this earlier Tortoise is that the idler gear stub axles are barely long enough to engage in their bearings. The Rev B ones are a sensible length.

So my plan is to re-engineer all my Rev B Tortoises as described above, not use the earlier 'Rev' Tortoise (keep it for some spares) and probably only re-engineer Rev C Tortoises when used on running lines. Incidentally, label colour is not a good guide to which Rev a Tortoise is - go by the pcb which, outside the case, should have only the number '1' on it if it's Rev C (or later).

Andrew

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grovenor-2685
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Joined: Sun Jun 29, 2008 8:02 pm

Re: Tortoise Auxiliary Switches

Postby grovenor-2685 » Thu Sep 10, 2009 11:19 pm

Something else to be unhappy about in this earlier Tortoise is that the idler gear stub axles are barely long enough to engage in their bearings. The Rev B ones are a sensible length.

I have not had any contact trouble with my tortoises but I have had two failures of the idler gear bearings.
The last idler gear that engages with the output rocker has the highest torque and hence is first to fail. I don't know what rev they are but the idler shaft has hemispherical ends that only just enter the bearings, the bearings just being half depth recesses in the side walls. In both cases the bearing was chewed away enough for the axle to be displaced. They were repaired by adding brass bearings.
I do think I contributed to the problem by having an installation with a lot less spring in the drive than the original tortoise wire, this increased the reaction at the end of stroke, but the design is certainly poor.
The Hankscraft motors, just to be different the final drive shaft just sheared off leaving no way to repair it except with an unavailable spare part.
Regards
Keith
Now convinced that Servos are the way to go, better in just about every respect including cost.

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Martin Wynne
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Joined: Mon May 14, 2012 4:27 pm

Re: Tortoise Auxiliary Switches

Postby Martin Wynne » Sun Dec 14, 2014 11:38 am

Update to this topic -- Gordon S reports that the circuit boards have now reached Rev.D at least, with much better alignment between the tracks and wipers:

tortoise_rev_d.jpg
tortoise_rev_d.jpg (188.16 KiB) Viewed 1435 times

Thanks to and © Gordon S

Discussion here: http://www.rmweb.co.uk/community/index. ... try1701125

Martin.
40 years developing Templot. And counting ...

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jim s-w
Posts: 1708
Joined: Wed Jul 30, 2008 5:56 pm

Re: Tortoise Auxiliary Switches

Postby jim s-w » Sun Dec 14, 2014 12:00 pm

I've operated several layouts with tortoises and must have used well over 200 in exhibition conditions by now. Not had any failures yet.

Cheers

Jim


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