Banging gears kart style!
Discussion
In a shifter kart, the gears are shifted with a lever mounted right behind the steering wheel. Pull towards it to upshift, push away to downshift.
Why aren't passenger cars like that? Why haven't they always been that way? I can reliably change gear in 50 ms which is a quarter of the time for an H-pattern transmission.
You'd have to have a pattern like R-N-1-N-2-3-4-5-6 and an indicator on the dash.
Why aren't passenger cars like that? Why haven't they always been that way? I can reliably change gear in 50 ms which is a quarter of the time for an H-pattern transmission.
You'd have to have a pattern like R-N-1-N-2-3-4-5-6 and an indicator on the dash.
You're essentially describing the operation of a conventional sequential gearbox - motorbikes behave the same way (although obviously it's a foot peg rather than a hand lever) as do many racing cars. The problem with that sort of gearbox for a road car is that they typically have straight-cut gears which, whilst more efficient than the helical gears in a normal car gearbox, tend to be very loud and suffer from more wear, hence having a shorter service interval. Especially if you change gear without disengaging the clutch (which is half the time saving).
Edited by kambites on Thursday 16th March 07:39
A helical gearset could be used but you'd have to have 3 full sets of dogs (and maybe even 6 synchronizers) because you couldn't just slide 3rd and 4th gear back and forth like a motorcycle's. The helical gears would "point" the same way so that a single thrust bearing could be used on each shaft, 1 deepgroove floating bearing and 1 angular contact bearing to take the thrust. Spur gears are a lot louder than helicals, and suffer fatigue failure earlier!
americancrx said:
Why aren't passenger cars like that? Why haven't they always been that way? I can reliably change gear in 50 ms which is a quarter of the time for an H-pattern transmission.
Because 99.99% of people don't care about the time to change gear.They care about PCP, reliability and 19" rims.americancrx said:
American column shifters used an H-pattern. They were notably awful, with linkages that had to transmit both twisting and pulling motion around several bends to get to the gearbox, well before modern geometry and materials made that workable.
I remember driving cars with column shifts and as you say the play was immense. Of course none of those vehicles were exactly new at the time I was driving them and probably slack had crept in over time. There again stick shifts of that era weren’t exactly precise either.Modern cars would be much better but I doubt if you could eliminate play altogether especially after a few years. Maybe instead of linkages you could use servos. It’s only one more thing to go wrong.
Anyway that’s going to be academic in a few years when everyone is driving autos.
The main reason is that it prevents you from 'block shifting' (eg. going directly down from 6th to 2nd when you're approaching a junction.
With a sequential, you have to go through each gear in turn, briefly engaging it before the box will let you engage the next. If you come to a stop in 4th, you have to shuttle through to neutral before it will then let you select 1st and move off again.
With a 6-speed sequential in stop-start traffic, this can turn into a major pain in the arse.
With a sequential, you have to go through each gear in turn, briefly engaging it before the box will let you engage the next. If you come to a stop in 4th, you have to shuttle through to neutral before it will then let you select 1st and move off again.
With a 6-speed sequential in stop-start traffic, this can turn into a major pain in the arse.
kambites said:
The problem with that sort of gearbox for a road car is that they typically have straight-cut gears which, whilst more efficient than the helical gears in a normal car gearbox, tend to be very loud and suffer from more wear, hence having a shorter service interval.
It's not the straight cut gears that are a problem (there's no reason you can't use helical cut gears on a sequential box), it's the dog engagement.This causes very 'clunky' engagement (especially if you make the dogs big and robust enough for road use), means you often have to slip the clutch a bit at standstill before the box will 'find' a gear, and the dogs wear too rapidly for most peoples' tolerance in road use (you might end up having to rebuild the box every 10K miles with new dog rings).
It's less of a problem with bikes, because they weigh much less (hence put less load on the dogs, wearing them slower) and typically do less mileage.
Edited by Equus on Thursday 16th March 08:42
Drawweight said:
I remember driving cars with column shifts and as you say the play was immense. Of course none of those vehicles were exactly new at the time I was driving them and probably slack had crept in over time. There again stick shifts of that era weren’t exactly precise either.
Modern cars would be much better but I doubt if you could eliminate play altogether especially after a few years. Maybe instead of linkages you could use servos. It’s only one more thing to go wrong.
Anyway that’s going to be academic in a few years when everyone is driving autos.
Out of interest recently I checked the PH Cars for Sale. 70% of the 2022 cars were automatic.Modern cars would be much better but I doubt if you could eliminate play altogether especially after a few years. Maybe instead of linkages you could use servos. It’s only one more thing to go wrong.
Anyway that’s going to be academic in a few years when everyone is driving autos.
Equus said:
It's not the straight cut gears that are a problem (there's no reason you can't use helical cut gears on a sequential box), it's the dog engagement.
You're probably right, but (slightly off topic) why is it never done in practice? Obviously it's rare to use sequential boxes in situations where refinement is a concern, but "rare" isn't the same as "unheard of". I'd have thought a helically cut sequential box would have had a place in some older supercars before DSGs became the norm? kambites said:
... but (slightly off topic) why is it never done in practice?
It is.Quaife for example give the option of both straight cut and helical cut gears on some of their products.
Trouble is, the overlapping portion of the Venn diagram for owners who want the ultimate in high-speed gearchanging, don't care about the clonks and shunting of dog engagement, don't care about the extra power loss, but do care about the whine of straight cut gears is almost vanishingly small.
americancrx said:
In a shifter kart, the gears are shifted with a lever mounted right behind the steering wheel. Pull towards it to upshift, push away to downshift.
A little threadrift if that's ok - IIRC the reason it it is this way round is because of the forces of acceleration / braking i.e it is easier to push the gearstick away when braking and vice versa.And if anyone ever gets the chance to drive a proper 250 shifter / superkart on track they should grab it with both hands as it is an experience you will never forget.
Equus said:
It is.
Quaife for example give the option of both straight cut and helical cut gears on some of their products.
Well you learn something new every day! Cheers. Quaife for example give the option of both straight cut and helical cut gears on some of their products.
LimmerickLad said:
…And if anyone ever gets the chance to drive a proper 250 shifter / superkart on track they should grab it with both hands as it is an experience you will never forget.
A 125 Gearbox Kart is more than enough to frighten lads who think they can drive after spending too much time down the local Teamsport.gazza285 said:
LimmerickLad said:
…And if anyone ever gets the chance to drive a proper 250 shifter / superkart on track they should grab it with both hands as it is an experience you will never forget.
A 125 Gearbox Kart is more than enough to frighten lads who think they can drive after spending too much time down the local Teamsport.https://www.youtube.com/watch?v=TCtz209gjYc
americancrx said:
In a shifter kart, the gears are shifted with a lever mounted right behind the steering wheel. Pull towards it to upshift, push away to downshift.
Why aren't passenger cars like that? Why haven't they always been that way? I can reliably change gear in 50 ms which is a quarter of the time for an H-pattern transmission.
You'd have to have a pattern like R-N-1-N-2-3-4-5-6 and an indicator on the dash.
What am I missing... why do you need two neutrals?Why aren't passenger cars like that? Why haven't they always been that way? I can reliably change gear in 50 ms which is a quarter of the time for an H-pattern transmission.
You'd have to have a pattern like R-N-1-N-2-3-4-5-6 and an indicator on the dash.
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