CitroJim's AX, C3 Picasso, Cycling and Running Tales

[mickthemaverick]

I'm finally starting to begin to recover from what it is that's been ailing me for almost a week. It's not Covid but it's felt like it... Turns out a close friend of mine had a virulent strain of 'flu a fortnight ago and we did, 'erm... have close contact

That's good to read Jim, especially in view of forthcoming plans!

[CitroJim]

That's good to read Jim, especially in view of forthcoming plans!

Exactly! Hugely looking forward to that Mick I'll be 100% by then

[Stickyfinger]

She's running beautifully and getting better with every drive...

Only because you are becoming deaf (by association) to all the rattles and creaks

[CitroJim]

She's running beautifully and getting better with every drive...

Only because you are becoming deaf (by association) to all the rattles and creaks

Speak up Alasdair! I didn't quite hear what you said there

[CitroJim]

Bringing the heater box into the warm and heating the clips did the trick

Disassembled with nothing broken...

Now to do the necessary repairs...

[CitroJim]

Pop rivets holding the motor and fan to the base of the housing drilled out to expose the speed control resistor pack...

The pack close-up...

I tried to carefully release it from its clips but it fell to bits as soon as I touched it...

The commutator looks good and there's lots of length on the brushes

I got some oil in to the bearings and on a test run the fan now runs nice and quietly... I used clock oil as I know this stuff is good for lasting a long time and being resistant to attracting too much dust...

With my AVO I determined it takes 6A on full speed... 72 watts!

As far as I can determine, measuring what was left of the old resistor windings the slow speed resistor total is made up of 1.8 ohms in series with 0.5 ohms, the mid-speed resistor...

A quick back of an envelope calculation suggests that on slow speed the resistors are dissipating getting on for 18 watts. I've ordered some 20W wirewound resistors to make a new pack and will put two in parallel for the slow speed so that they will run nice and cool.

There's loads of room to accommodate them, either in this convenient recess..

The wires visible are those that originally went to the old resistor pack...

Or I could even mount them in the outflow area where they can lay flat and take advantage of some forced-air cooling!

The pop rivets will be replaced with M5 setscrews, nuts and washers secured with a dab of Loctite...

[CitroJim]

Rather than use speed control resistors in Bluebell's blower I thought about doing it a bit differently... Maybe a little more elegantly than a bunch of crude wirewound resistors...

I have a few MJ11015 power Darlington devices left over from when I used to repair Xantia blower speed regulator modules... I still have a few of the complete modules in my spares stash too...

These devices can pass, with a decent heatsink, 30A so adequate for the job...

On this rainy morning I knocked up a very rough Proof of Concept controller using a little pot to vary the speed of the blower...

It works well and I can choose the intermediate speeds, measure the pot resistances and then substitute fixed resistors in the final design...

It'll need a decent heatsink and like in the Xantia, if I mount it in the blower outflow it can enjoy a bit of forced-air cooling...

Now to build it properly and soak test it...

[myglaren]

Elegant solution Jim.
Why not keep the pot, just use a prettier one.

[CitroJim]

Elegant solution Jim.
Why not keep the pot, just use a prettier one.

It's a lovely thought Steve and I think that may be possible as the blower speed knob has the right 'D' profile to fit a pot shaft...

The big issue is to get behind the dash to swap the original switch for the pot... S1 AX dashes are best when disturbed as little as possible...

They usually object to being disturbed by cracking and falling to bits

[CitroJim]

I've made a bit of a prototype this afternoon to try and assess heatsinking requirements and potential mounting options within the blower housing...

Initial tests suggest the heatsink can be a bit smaller...

I need some heatsink compound and don't have any... eBay here I come...

[CitroJim]

I procured some heatsink compound from Amazon for my AX blower regulator project...

I was intrigued to see they sent me a pair of what looks for all the world like miniature condoms with it

Condoms for Audi drivers perhaps

[mickthemaverick]

Condoms for Audi drivers perhaps

Surely your logic is reversed there Jim, Audi drivers would need giant ones!!

[CitroJim]

Condoms for Audi drivers perhaps

Surely your logic is reversed there Jim, Audi drivers would need giant ones!!

Indeed you are absolutely right Mick

[CitroJim]

Due to how the blower speed switch works on the AX I've gone for a little redesign of my blower speed controller...

Using a PNP Darlington in the negative side of the circuit was going to cause a problem so I've swapped to an NPN Darlington, an MJ11016, the complementary partner to the MJ11015...

I had a couple lurking on a Chinese copy Xantia/XM speed regulator... Ages ago I bought an XM withy a baffling blower issue. It had a brand new speed regulator module fitted but still wouldn't go...

A quick inspection showed this beautifully built module had a pair of NPN MJ11016 Darlingtons fitted rather than the correct PNP MJ11015...

It was never, ever going to work... On that XM I replaced it with one of my rebuilt genuine regulators and it was then all good...

How such a fundamental mistake could be made amazes me to this very day

I've reworked my AX prototype using the MJ11016 and now I have some heatsink compound under it the whole thing is running as cool as a cucumber at half-speed

And I found no need to wear those little condoms when applying the compound Not that they'd fit anyway

I've not had a lot of time today due to a lot of parkrun admin and necessary domestic work but I'm hoping to have the blower back in and working after parkrun tomorrow so that I can join Zel and his R25 at the Stony New Year's Day classic car meet...

Fingers crossed

[NewcastleFalcon]

...and there was me thinking Darlington Co Durham had another claim to fame, but no some bloke called Sidney Darlington invented The Darlington transistor in 1953 according to this...

https://www.electrical4u.com/darlington-transistor/

Regards Neil