By-passing k-series inertia switch

[MartinWoodham]

we're trying to use G to distinguish between a kerbing (don't want to trip the fuel pump) vs crash (do want to trip it).

There may be situations that are low-G but you'd want it to trip eg car does a fairly gentle roll and ends up upside down.

 

For road use you obviously would want significant protection, and for track use you'd presumably take the risk since there are plenty of marshalls about and the risk exposure is very low. Plus the emerald controlling the fuel pump relay anyway.

 

I don't see any problem with a hard-wired switch as originally proposed, to switch between track and road mode. It's simple and reliable.

 

Could the existing inertia switch be resonating with "rapidly alternating, mainly vertical g" from a rumble strip, and hence be seeing a higher peak than really exists?

 

In which case the accelerometer solution might allow more discrimination? (BTW Colin, keep going on the water fuel guy, we've nearly got him!)

 

 

Martin

supersported ex-Roadsports B

[henry21p]

I'm sure Adam will crash test it for you if you want? 😬 😶‍🌫️

[Colin Mill]

I suspect that there may well be some resonance effect with the existing switch that could account for the rumble strips triggering it. I also wonder if the switch is directional and perhaps, as mounted, more prone to vertical g than horizontal g. Perhaps someone who has taken one apart could comment on that.

 

I'm concerned that an accelerometer based unit should not have any loop-hole in the strategy and I would like to see an easy way of checking it periodically.

 

The accelerometers themselves have a self-test pin so the micro can check if the accelerometer thinks its OK. Since they are used in safety critical applications this self test is supposed to actually apply some force to the accelerometer element so a proper front to back check is involved. So, in principle it could have a fail safe action with suitable flashing light warning so you don't end up stripping the car to its component parts trying to get it started when the switch has tripped 😬

[Simon.Rogers1]

I'll drive it over some rumble strips.

 

I seem to drive over them every other week end anyway 😬 😬 😬 😬 😬 😬 😬

[Colin Mill]

as for zero g... I guess the biggest/longest jump is The Snake @ Longcross... and I should think that is in reality only a tenth or so of a second. THough feels longer!!!

Well, I guess you could be doing 120 mph up a 1 in 4 and go over the brow to a minus 1 in 4 the other side in which case the zero g would last about 3 seconds but I reckon the fuel switch tripping at this point might be worthwhile in anticipation of the crash - the CAA would approve I'm sure 😬