Well knowing the series30 has a low ratio of 2.7:1
I just added a hair of safety margin and raised that to 2.6
(since as soon as the belt is fully engaged it wants to raise on the driver)
that times the chain ratio gives us a
final ratio of 15.6:1
with 3100 rpms (full lock rpms) and 18" wheels that means we talk 10.64 mph
Or if you want it the other way around:
take the 2.7:1 low ratio completely to get to 16.2:1 overall ratio
and add the safety margin to your rpms (+100 rpms)
and with 3200 rpms on 16.2:1 and 18" wheels we get to a calculated speed of 10.58 mph
both round to be roughly 11 mph.
any slower than that and the clutch might want to start disengaging again (burning the belt/shoes)
Wheel size is an essential part of the gear ratio, most people forget about that.
since in the end you want the engine to push you along a road not just spin a wheel, right?
If you alter the wheelsize of an existing setup you mostly want to adapt your ratio to that.
And in such cases it's fairly easy to do..
take the ratio you got and divide by the wheeldiameter you got
then multiply with the wheeldiameter you want (6/18)* 15
and you end up at 5:1
So 6:1 on 18" wheels behaves almost the same as 5:1 on 15" wheels
(acceleration, top speed etc. all calculate to the same values)
here some generic kart/engine setup with 18" on 6:1 and 15" on 5:1 for comparision
(keep in mind clutch engagement here is assumed to be 2200 rpms)
KartInfo by kartcalc.net:
Code:
[FONT="Verdana"]
[B][U]KART[/U][/B]
[INDENT][I]RW diameter[/I]: [B] 45.72 cm | 18 in[/B]
[I]Total weight[/I]: [B] 200 kg | 440.92 lbs[/B]
[/INDENT]
[B][U]ENGINE[/U][/B]
[INDENT][I]Original HP[/I]: [B] 7[/B]
[I]Asummed HP[/I]: [B] ~7[/B]
[I]Torque[/I]: [B] 13.85 Nm | 10.21 ft lbf[/B]
[I]RPM[/I]: [B] 3600[/B]
[/INDENT]
[B][U]TRANSMISSION[/U][/B]
[INDENT][I]Final ratio[/I]: [B] 6:1[/B]
[I]TC type[/I]: [B] series 30 6" driven[/B]
[I]Lowest ratio[/I]: [B] 16.2:1[/B]
[I]Highest ratio[/I]: [B] 5.4:1[/B]
[/INDENT]
[B][U]PERFORMANCE[/U][/B]
[INDENT][I]Max Wheel Torque[/I]: [B] 224.37 Nm | 165.49 ft lbf[/B]
[I]Min Wheel Torque[/I]: [B] 74.79 Nm | 55.16 ft lbf[/B]
[I]Acceleration[/I]: [B] 2.79 m/s² | 9.15 ft/s²[/B]
[I]Top Speed[/I]: [B] 57.45 km/h | 35.7 mph[/B]
[/INDENT]
[/FONT]
KartInfo by kartcalc.net:
Code:
[FONT="Verdana"]
[B][U]KART[/U][/B]
[INDENT][I]RW diameter[/I]: [B] 38.1 cm | 15 in[/B]
[I]Total weight[/I]: [B] 200 kg | 440.92 lbs[/B]
[/INDENT]
[B][U]ENGINE[/U][/B]
[INDENT][I]Original HP[/I]: [B] 7[/B]
[I]Asummed HP[/I]: [B] ~7[/B]
[I]Torque[/I]: [B] 13.85 Nm | 10.21 ft lbf[/B]
[I]RPM[/I]: [B] 3600[/B]
[/INDENT]
[B][U]TRANSMISSION[/U][/B]
[INDENT][I]Final ratio[/I]: [B] 5:1[/B]
[I]TC type[/I]: [B] series 30 6" driven[/B]
[I]Lowest ratio[/I]: [B] 13.5:1[/B]
[I]Highest ratio[/I]: [B] 4.5:1[/B]
[/INDENT]
[B][U]PERFORMANCE[/U][/B]
[INDENT][I]Max Wheel Torque[/I]: [B] 186.98 Nm | 137.91 ft lbf[/B]
[I]Min Wheel Torque[/I]: [B] 62.33 Nm | 45.97 ft lbf[/B]
[I]Acceleration[/I]: [B] 2.79 m/s² | 9.15 ft/s²[/B]
[I]Top Speed[/I]: [B] 57.45 km/h | 35.7 mph[/B]
[/INDENT]
[/FONT]
Side note:
Wheel torque here is the torque the wheels are driven by (engine->chain->wheel);
the torque the wheels pushing against the road with - again is identical
224.37Nm (doesn't matter which one you pick really)
times 15 divided by 18 turns out to be 186.975 (some rounding involved
)
same mathematical concept as above
that's why acceleration doesn't change..
'sid
