Spigot bearing clearance

[DeTRacted]

There is no inrush current peak when applying a DC voltage to an inductive load. As the magnetic field builds the inductor produces a back-emf which opposes current flow, so current increases asymptotically from zero to finally reach the maximum value determined by the coil DC resistance.

When you remove the supply from an inductive load the magnetic field collapses suddenly and produces a large back-emf 'spike'. That can arc across a relay contact as it opens, causing burning and failure of the contact in time. A diode connected across the inductor  so that it is reverse biassed to the normal supply polarity will be forward-biassed by the back emf, and so effectively shorts out the spike. The diode does need to have a suitable surge-current rating.

[rogerguzzi]

Hello All

               Thank's both for the information(still not sure I understand it!) I am thinking I may just use my home made logic box to drive a large relay(I have a Lucas one on the shelf) a bit over kill I know! or even a modern type fitted to a plug in base?(I have a few of those)

At least the gearbox/overdrive is back in and bolted down(I am Kn****d)

I think I will fit the rebuilt diff I bought at Stoneleigh before I fit the prop shaft and refit the exhaust system.

Still not bad for a 73.5 year old?????(but it all seems to take a lot longer now!)

Roger

[rogerguzzi]

Hello All

               I fitted a 1N4002 diode which is rated at 100v @ 1 amp

I have a 1N5406 which is 600v @ 3amp

would this be a better choice?

Roger

Ps I have various capacitors what would be the value I would need to put across the contacts?  

[DeTRacted]

Those currents are the continuous ratings Roger.  The 1N4002 will take 30A non- repetitive surge current which would be fine . The reverse voltage rating though might be considered a bit marginal as it's possible that spikes exceeding its surge rating of 120v could possibly happen.  I think I would use the 1N5406 just to be on the safe side - as its surge ratings are considerably higher. 

The  exact value of capacitor to use if you go that route instead (you don't really need to do both) is a bit less easy to determine as it really depends on the other circuit parameters but as a rule of thumb  0.1 microfarad should be adequate. Again, it needs to have a suitable voltage rating to handle possible voltage spikes so perhaps 250v. 

[rogerguzzi]

Hello Detracted

                           I will change it for the 1N5406 I did not want to fit another relay(there is enough extra wiring on the car with Microsquirt etc!)

Roger

[Nick Jones]

Sounds like we have someone on board who really knows about electronics rather than my bodgit and hope version...... this is good!

[122344]

if you a happy with a rely box with lights have you considered a a momentary switch to engage a latching circuit that will de-energize the OD circuit if you shift out of 4th gear. The OD will not re-energize with out the momentary switch being reapplied.

[rogerguzzi]

21 hours ago, 122344 said:

if you a happy with a rely box with lights have you considered a a momentary switch to engage a latching circuit that will de-energize the OD circuit if you shift out of 4th gear. The OD will not re-energize with out the momentary switch being reapplied.

Hello

        My home made box drops it out when I come out of 2nd,3rd or 4th but I have to reset the O/D switch(I thought about that when I built it but could not find a circuit drawing I understood)

It did not drop out between 3rd and 4th before but I have modified the actuator in the gearbox so it does now 

I can not even find the one I built now!

Roger