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Overdrive in 2nd gear and logic switching (moved from "miss-fire over 4000 rpm"))


Hamish
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9 hours ago, Escadrille Ecosse said:

So then, going back to this circuit from Andy

Would it be possible to achieve the clutch dropout function by filing a slot at the neutral position of the 3rd/4th interlock cam?

I don't see why not. If you wire the interlock switch in place of the clutch switch in Andy's circuit (and just take the relay 1 contact 86 direct to earth), it would drop the OD out as soon as the switch opens. If you can make the switch open when changing between 3rd and 4th then you're in business.

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7 hours ago, rogerguzzi said:

Hello All

             I have done that on a single rail gearbox I made a new cam and it works on 2nd as well and fitted an extra switch

I have also done it on a 3 rail gearbox but just for 3rd and 4th (can not find photo will look later)

Thanks Roger, I was hoping that if it wasn't a daft idea then someone on Sideways would have trodden the path before me.

Pete, yes. Thinking about Andy's wiring drawing then my thought was that adding a third relay off the 3rd/4th switch instead of the clutch switch would do the job.

This work??? Presumably adding a second gearbox switch for 2nd gear in parallel as in Roger's pic if wanted.

580114804_IMG_20210912_0002small.thumb.jpg.b95da7a3749afcd69bd7d1d69f904849.jpg

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1 hour ago, Escadrille Ecosse said:

This work??? Presumably adding a second gearbox switch for 2nd gear in parallel as in Roger's pic if wanted

Potential problem there is your 12v is shared across relay coils 1 and 3, so they'd need to be 6v units. You'd be fine to wire the 3rd/4th switch (and parallel 2nd switch) in directly where you've got the R3 output contact - it won't be taking much current so doesn't need to be on a relay, I don't think.

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Ah wait, that would mean that if the OD button got stuck or held on you'd have no inhibit, so isn't a great idea. Maybe leave the 3rd/4th switch where it is but also take another pair of cables off it for the latching part of the circuit. The inhibit switch has got two pairs of spade terminals hasn't it?

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Are you over-thinking this? I can't see what you are trying to achieve with the third relay.  If you have the interlock opening between 3rd/4th the circuit automatically drops out as you go through neutral without the need for another relay, since power for RL1 is removed when the interlock opens.  What you don't have without the clutch switch or an equivalent on the dashboard, is any means of turning off the overdrive yourself except by changing gear. 

(By the way, the TR/saloon box already has interlock opening in neutral between 3/4 AFAIK - at least, the  ex-2000 box in my '3A does) 

 

 

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2 hours ago, Hamish said:

My inhibit switch wiring is switch to switch 

od on 2, 3, 4 

don’t know what the nonwired switch is?

i guess reverse light switch ?

it’s a tr6 box

 

D98EDDB9-CC21-4CC9-ACB0-50C6F4B53C25.jpeg

Hamish, TR box three rails go - reverse, 3/4, 1/2 from left to right so the unused switch is reverse and the other two are wired in parallel to give you OD 2,3,4.

@PeteStuppsgot with the relay voltage. Took me a while to work out the rest as I tend to think in pictures rather than text, especially with the difficult stuff like electrical logic!

1 hour ago, DeTRacted said:

(By the way, the TR/saloon box already has interlock opening in neutral between 3/4 AFAIK - at least, the  ex-2000 box in my '3A does)

Yes, that's right as the switches act directly on the selector rods in the extension.

1 hour ago, DeTRacted said:

Are you over-thinking this? I can't see what you are trying to achieve with the third relay.  If you have the interlock opening between 3rd/4th the circuit automatically drops out as you go through neutral without the need for another relay, since power for RL1 is removed when the interlock opens.  What you don't have without the clutch switch or an equivalent on the dashboard, is any means of turning off the overdrive yourself except by changing gear.

Overthinking??? Moi? Quite probably Rob :laugh:

However the primary requirements for the overdrive for me is that is it user selectable up and down shifts. Switching between OD 3rd and 3rd is a good B road combination. Which is what the standard switch arrangement gives.

Adding in operation on 2nd is a nice to have but that is relatively simple to do 'mechanically'.

The only real nice to have here for me that I can't do without some logic of sorts is a way of knocking off the OD automatically when changing gear. With the column switch I find it no problem coordinating the two physically but if one forgets then 2nd to 3rd with the OD on is a big jump with the small engine.

So it is only a nice to have for me but not at the expense of losing any of the existing functionality. And out of my comfort zone mentally so an interesting challenge

Therefore the circuitry would need to allow for switching off the OD without a gear change and I would want to do this through the same column switch so it effectively replicates the existing control.

Which I realise now thinking about what you have said my circuit doesn't do. :pinch:

So I'm off to do more sketching :biggrin:

Edited by Escadrille Ecosse
stet
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Here is a way of having sequential on/off switching with a single momentary switch (in this case on the gear-stick but it could be anywhere). It uses a bi-stable relay and was designed for a J type but is easy to adapt for an A or D type. The two transistors shown could be replaced by a single TIP120 : 

1303932843_singleswitchODcct.jpg.38fa07230922a9dab06ce0b27ab637b7.jpg

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Ho, ho. Cheers Rob.

I had been thinking that the only way of doing this was with a changeover circuit using a latching relay. I realised I would need a diode in the system to stop backflow but I assumed the latching relay would take care of the switchover logic without needing transistors.

The LED on the solenoid is a nice fault fining touch.

This was my mechanical engineer's 'hydraulic' logic circuit

IMG_20210913_0001R.jpg

Am I way off the mark?  :biggrin:

Edited by Escadrille Ecosse
finished post!
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The problem with the latching relay is you need a pulse to re-set it when the interlock opens, for the 'logic' function - which is what the transistors do. I don't think there is any other way to do that. You also need to find a way to automatically ensure it always starts in the 'off' position, because as-is it stays where it was last set.   That circuit is for a TR 'box with the off-in-neutral function. 

In your sketch, if the latching relay is ON and the interlock kicks RL1 off because you change gear, the next time you operate the switch it turns the latching relay off again so you don't get OD. You would have to push the button twice to get overdrive on again.  I think you might soon find that irritating - sometimes one push needed, sometimes two. 

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7 hours ago, DeTRacted said:

Here is a way of having sequential on/off switching with a single momentary switch (in this case on the gear-stick but it could be anywhere). It uses a bi-stable relay and was designed for a J type but is easy to adapt for an A or D type. The two transistors shown could be replaced by a single TIP120 : 

1303932843_singleswitchODcct.jpg.38fa07230922a9dab06ce0b27ab637b7.jpg

Thanks for that diagram Rob. And for you explanation as to why my 'hydraulic' analogy can only take me so far.

This is bringing back vague memories of my Dad trying to teach me this sort of stuff when I was very young and solid state devices were 'new'.

31 minutes ago, mpbarrett said:

starts to make a PiC processor seem like a good option :)

mike

You say that Mike but with a wiring diagram it's just a bit of soldering and hey presto. Stick it in a wee box with a heat sink for the transistor and some potting compound and it's job done. Pretty much a mechanical activity that I can cope with.

With a processor I essentially have to create my own wiring diagram and then work out how to code logic it to make it work. Both of which are skills I think I have successfully failed to demonstrate :laugh:

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Unfortunately I'm in the wrong place to put pictures up (currently sailing up the Med) but "Shacktune" sells a momentary logic box for the A-type O/D's on the saloons. I haven't looked into it in great detail yet, although I have one sat on the shelf waiting for me to do so.

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43 minutes ago, thebrookster said:

Unfortunately I'm in the wrong place to put pictures up (currently sailing up the Med) but "Shacktune" sells a momentary logic box for the A-type O/D's on the saloons. I haven't looked into it in great detail yet, although I have one sat on the shelf waiting for me to do so.

This is on his ebay site. Says J type in the title but description is for any of them

https://www.ebay.co.uk/itm/143845471843?mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338722076&toolid=10001

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On 9/13/2021 at 7:42 PM, Escadrille Ecosse said:

Thanks for that diagram Rob. And for you explanation as to why my 'hydraulic' analogy can only take me so far.

This is bringing back vague memories of my Dad trying to teach me this sort of stuff when I was very young and solid state devices were 'new'.

You say that Mike but with a wiring diagram it's just a bit of soldering and hey presto. Stick it in a wee box with a heat sink for the transistor and some potting compound and it's job done. Pretty much a mechanical activity that I can cope with.

With a processor I essentially have to create my own wiring diagram and then work out how to code logic it to make it work. Both of which are skills I think I have successfully failed to demonstrate :laugh:

quite understand, nothing wrong with relay logic. Some of the PLC (programable logic controller) use a programming language that is based on relay logic.
The nice thing about simple relay cct's is that they can be quickly hacked to get them to work if something breaks (think dark wet night on RBRR).

Mike

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2 hours ago, mpbarrett said:

nothing wrong with relay logic

Indeed! But it can get a bit ridiculous, for example:

2017-08-31_InterfacePanel_DSC_8595.thumb.JPG.f15e1cf7919582e5da79735240b06b73.JPG

DSC_7948.thumb.JPG.25c7ca5ae4ce6044e1188d06aaea028d.JPG

Around 180 relays used to control some 750V DC switchgear at a Network Rail site in London, the cabinet is 1.8m tall (tripod device is recording electro-magnetic output). This was designed and installed in 2018 believe it or not; was great fun to stand next to it and hear everything clunking away, with all the lamps blinking.

The following year I went back and added some similar functionality using a PLC the size of a sausage roll...

Personally I love clockwork stuff but if it's going to be a bit complicated, I'd go for a programmable controller. So much easier / cheaper to tweak the logic in software compared to re-wiring.

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1 minute ago, PeteStupps said:

The following year I went back and added some similar functionality using a PLC the size of a sausage roll...

Personally I love clockwork stuff but if it's going to be a bit complicated, I'd go for a programmable controller. So much easier / cheaper to tweak the logic in software compared to re-wiring.

Yes. I spent a large part of my working life taking out the old electro-mechanical and electro-pneumatic control systems as part of processing plant refurbishments.

I know what they can do, but like a flat screen TV or heart surgery, I prefer to leave the actual construction to the experts in the field :biggrin:

I did become slightly concerned about security when the shift from PLC to PC based network systems began but the experts told me I was being ridiculous and what did I know just being a 'clanky' and a dinosaur :ninja:. Hey ho!

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4 hours ago, Escadrille Ecosse said:

I did become slightly concerned about security when the shift from PLC to PC based network systems began but the experts told me I was being ridiculous and what did I know just being a 'clanky' and a dinosaur

...and your concern was correct as witness the Iranian centrifuge plant full of Seimens PLCs, sabotaged by the Stuxnet virus.  The problem isn't necessarily the system itself either but the daft b*****s who insist on it being connected it to the internet, though even an air-gap doesn't help there is an unprotected USB socket.  

 

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4 hours ago, DeTRacted said:

The problem isn't necessarily the system itself either but the daft b*****s who insist on it being connected it to the internet, though even an air-gap doesn't help there is an unprotected USB socket. 

Yes, any system requires lots of people to do exactly the right thing all the time, every time is guaranteed to fail at some point.

Witness the case of U-1206. Forced to the surface by flooding arising from incorrect use of the toilet operating system, it was attacked and sunk by British forces on it's first patrol off Scotland. :blink:

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Hi Folks,

this is my version of the OD Logic Box. As you can see based on relays and works eually as well as any on the commercial market.

A 12v momentary pulse goes in at #2

This finds its way to the OD relay and supplies power to the solenoid.

At the same time the OD relay supplies 12V back into the relays to switch over Rly1 AND to hold the OD relay in the ON position.

If you activate the On/Off momentary switch again it shuts off power to the the OD relay coil so OD drops out.

Or - if you change gear the earth circuit for the OD relay is broken (as normal) and the system goes into OFF mode.

It all fits nicely on Vero board and in a small box.

For the real dinosaurs there is an optional relay for a night time dimmer circuit for the warning LED.

The 12v momentary input could be swapped for a negative pulse by using another real (win/win situation)

I can supply these ready for action at £25.  The momentary switch I use is from the steering column on a stalk (I like it that way)

 

Roger

image.thumb.png.0516dd549d8ff2e760b1b1c930cf98dc.png

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2 hours ago, Escadrille Ecosse said:

@RogerHSold. I'll give that a go :thumbsup:

I'll PM you later

Hi Colin,

before you get too excited the above circuit is for an A type OD.  It would power a J type but needs the A type relay fitting. I don't know about  other OD's.

The momentary switch could be a push button (as  have) or a toggle switch - it only needs the shortest possible pulse (1/2 second or less).

 

Roger

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1 hour ago, RogerH said:

Hi Colin,

before you get too excited the above circuit is for an A type OD.  It would power a J type but needs the A type relay fitting. I don't know about  other OD's.

The momentary switch could be a push button (as  have) or a toggle switch - it only needs the shortest possible pulse (1/2 second or less).

 

Roger

Roger, no worries. I have a J type in the car and so didn't bother with the relay but fitting one isn't a big issue and probably safer anyway. I've got realys for pretty much everything else :biggrin:

I am impressed as always with those who can work out this sort of thing

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I wanted a two-way centre-biased momentary toggle switch for my J-type box, flick down for OD on , flick up for OD off, plus the logic from the interlocks. That way I don't need a warning lamp as operation is obvious, so this is what I did:

2020370421_myODlogic.jpg.794bf26b89fbc2115179635d6f279a60.jpg

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