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Did you ever hear of the 80:20 rule? You know, the one where you get 80% of the product with 20% of the effort (and, of course, the remaining 20% of the product from the last 80% of the effort!).
We're nearly there.
We're nearly there.
Honestly, this weekend we'll see it walk...okay, maybe next weekend...or the next...or the next!
1/7:
In search of alternatives to speed controllers for starter motors (200 quid or so!): relays. We want a complex
relay which has two double position switches in it as follows:
John looked for these in the catalogues in vain. The 30Amp ones they had were over £50 each. His Toyota's starting relay is rated at 100Amps, so John thought 'Get a couple of scrap ones'. This he did, at the nearby Japanese car scrappers. He got two FO(translation: Fairly Outrageous...or something like that!)-sized ones for XXX (cheap!!!), which are the relays which power the glow-plugs in a diesel car. John says: "I thought I had it sorted, but my tiny mind had overlooked the fact that the solution used a two-switch-two-way relay. This effectively acts like four single switches. So what we need is two more relays to give the following configuration:
"I'll test the two I have got to get the motor to go one way, then go back to the scrappers for two more. Simon, we need some ideas on how we will supply the four switches with the 12v trigger voltages. What we need to power only two of the relays at any one time and to have on 'off' position where none of the relays are powered. Probably some form of light-weight three-way switch which the radio-control can actuate would be ideal?"
6/7:
John has wired up the large starter motor. All it needs are a few ventilation holes drilling in the end cap. He was going
to do it last night, but his new drill (previous one a victim of STOMP!) was faulty, so it goes back tonight. It will then
need to be re-united with the armature, (if Carl actually gets it to Tim to weld!).
In the continuing search for cheap (free!) components, John goes diving in the local skip:
8/7:
Tim has welded another sprocket onto S.M. - I'll be picking it up tonight. Haven't heard, but Geoff should have sprockets
ready for W. Ms.
Dodgy switch that nearly cost John his life probably not suitable (you're right, John - definitely NOT worth scrabbling
around in skips for). I took it apart and the internal springs are an intrinsic part of the switching mechanism - so it
looks to me altogether too well sprung for a servo. I think we need to spend a couple of quid on a proper one.
I plan to fiddle around with relays (possibly a better swoop than the switch) and motor mountings tonight. Anyone care to
join me?
Reg Rads
Carl ~#:)#
9/7:
The way that the power side needs wiring up:
The control side needs to be wired such that Relay 1A and 1B are powered OR 2A and 2B.
John
12/7
There are 10 more photos, but I have not managed to get them scanned in yet. I did get the sprocket ground down to the
correct thickness on the large starter motor. However, I found that the chain still kept coming off if the chain were out of
alignment by more than a few degrees. I think that the problem is that there are very few teeth on that sprocket. On a
bicycle, the minimum number of teeth I have seen is 15, and on the lawn mower, the two sprockets were perfectly in-line.
Anyway, I have made a couple of collars for the shaft which fit either side of the sprocket. They seem to work even though
they are held on with a couple of jubilee clips. Perhaps we need to weld a couple of steel washers on instead? I have wired up the relays and modified a car window switch to give us the three-way switch we wanted, all I need to test it are some
more spade terminal connectors. Carl, could you bring these in with you tomorrow?
John
14/7:
I connected it all up last night and it works. It's a bit noisy, I don't think that the big starter motor is as smooth
running as the small one. I've got it in the office for Carl to collect.
John (x35236)
22/7:Website live