Clutchless shifting a dog gearbox.
Clutchless shifting a dog gearbox.
(OP)
this question is kinda related to thread78-142609: Clutchless shifting a dog gearbox.. basically we are looking to install a jerico dog box in our circuit race car and are looking to incorporate a flat shift device so we can shift at full throttle on upshifts. From what i understand i will need a microswitch on the shifter and so as soon as the shifter moves the ignition will cut to reduce the load and enable the shift to take place. We have a 2 stage msd ignition on the car so i can wire this microswitch into the 2 step limiter to provide the ignition cut.
my question is firstly where can i source a suitable microswitch to detect shifter movement i.e has anyone setup something to this.. also obviously as we'll be clutching on down shifts i don't want this shifter movement to cut the ignition so i figured by wiring a clutch switch in to the circuit if the clutch is depressed it would bypass the shifter microswitch... just wondering whether anyone had a similar setup and could advise .....
cheers....
my question is firstly where can i source a suitable microswitch to detect shifter movement i.e has anyone setup something to this.. also obviously as we'll be clutching on down shifts i don't want this shifter movement to cut the ignition so i figured by wiring a clutch switch in to the circuit if the clutch is depressed it would bypass the shifter microswitch... just wondering whether anyone had a similar setup and could advise .....
cheers....





RE: Clutchless shifting a dog gearbox.
Here's a common one.
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If you are using an automotive H pattern shifter, things are a bit more complicated ...
RE: Clutchless shifting a dog gearbox.
RE: Clutchless shifting a dog gearbox.
With an external rail, for sure you can put force transducers in both shift rails, detecting both compression and tension - no other choice. If you want to do full throttle shifts you'll probably also need to know if the transmission is in neutral between gears because of different time to shift between 2-3 (between gates) and 3-4 (same gate). Clutch pedal switch to disable the system should work. Beyond that, can't help, never seen it done.
If the base of the shift linkage is tied to the transmission with a locating rod (many rod-shifted transverse gearboxes are like this) then you might be able to cut the number of switches in half by putting the switches on that rod instead of on each rail, since whatever force is going through each rail is going opposite through that rod. If there's no such rod but you can get access to where the base of the shifter is mounted, you might be able to do something similar.
RE: Clutchless shifting a dog gearbox.
I do have a little experience with the dog-rings, from using a 4th-gear-only Jerico as a foolproof IN/OUT box in my blown-alky mini pulling tractor. I wanted to avoid the hassle of an input-shaft-brake for when the slipper clutch drags, and it works well- makes it easy for me to believe the "clutchless" upshifting claims.
RE: Clutchless shifting a dog gearbox.
One thing I learned the hard way, when I pull an upshift, just 'blip' the throttle and on downshifts, use the clutch...I've never broken a box using this method (knock wood), at least not yet. Full power shifts are tough on equipment. I did a few on my drag cars back in the late 50's, early 60's. I also rebuilt a lot of drive trains.
Rod
RE: Clutchless shifting a dog gearbox.
In drag racing the small fraction of a seconds gain and the very short required service life makes full power shifting viable in drag racing, but for any other forms of racing, the extra weight of the stronger components needed to withstand full power shifts for the duration of a race meeting will negate the small time savings.
Regards
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RE: Clutchless shifting a dog gearbox.
RE: Clutchless shifting a dog gearbox.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Clutchless shifting a dog gearbox.