Julian Roberts wrote:Despite Martin's warning I did try the pair of larger capacitors (the right way round) on the circuit of two motors - the effect was quite dramatic, the motor threw at an alarmingly fast speed - but the good news is that the return throw seemed to be the same speed (I wasn't going to investigate by repeating the process for fear of damaging the motor). Nigel (who is out of the country just now) when sending them to me suggested just one small one might do the trick but wasn't clear which one in the diagram that would be.
If you use capacitors then they will charge up to the peak voltage, likely around 20V, the size won't make much difference (unless really very small). Tortoises are usually to fast at 12V, best at about 9V which is why the half wave circuit is quite good for them. If you use capacitors it has to be two, just using one will give the motors a smooth 20V in one direction and leave them with the half wave 10V in the other. I doubt he meant that.
He sent this diagram in case it was needed
You can add more diodes like that to reduce the voltage, each diode in the chain dropping about 0.7V, so to drop from 20V to 10V you would need a chain of 14 diodes! IMHO accept the speed variations or can the half wave system and get two small PSUs, ideally 9V ones as as has been suggested.
Regarding flux etc, Noel thanks for your answer too, here are the options from one place. I've found that solder tags, microswitch terminals, etc, take the solder very easily, acting as though they are already tinned - is that likely? I assume that a tin of "Fluxite" isn't what I should be after.
Definitely not fluxite. Usually component leads, solder tags etc. are pre tinned, microswitches not always as some are intended for push on connectors. But clean copper will solder well with cored solder, no need of extra flux.
Regarding electrical solder I have got one of those packets of Carrs that contain sufficient for someone of a more anorexic approach than mine. None of these say "electrical"
In an earlier post you did say you had used electrical solder, was that the Carrs? I didn't think he did any cored solder.
For any electrical wiring I would recommend old fashioned lead 60%/tin 40% solder with rosin flux core. eg.
https://cpc.farnell.com/duratool/d01681/solder-wire-sn60-pb40-0-7mm-100g/dp/SD01535?st=60/40%20100gh