As the boys and I were trundling through the 50 limit on the A1 recently, I was asked by the elder (nearly 21) what "overdrive" was. His boss had referred to son being in overdrive as son stacked pallets with the fork-lift. I thought I knew, my dad having been a Motor Engineer and owner of the village garage, but talking to someone with their attention span limited by recent late nights made me struggle. Checking with online dictionaries and Wikipedia brought no enlightenment; I thought their definitions were rubbish.
So I'm inviting the collective brains of the Backroom to give me a succinct definition of "overdrive" in its motoring context.
Over to you ...
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Overdrive:
1. A gear ratio where the output shaft spins faster than the input shaft
2. A person driving beyond the speed at which they guardian angel is flying
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3) A 1970's rock(ish) band....
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In a lorry, Aberdeen Overdrive is coasting downhill out of gear!
Something we never do now, of course :)
Pat
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>>In a lorry, Aberdeen Overdrive is coasting downhill out of gear!
When I was a kid my dad and his mates used to call that 'using silent fifth'.
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In a lorry Aberdeen Overdrive is coasting downhill
As in that big hill leading down to the roundabout with the junction to the river bridge on the main road from the south? Eeek!
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An in-between gear ratio, usually on third and top gears, giving the sequence: third, overdrive third, fourth, overdrive fourth. (20 words)
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A lazy person that is noted as doing some thing faster than his/her usual pace.
Cruise control for the under 25's is the new 'overdrive'
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Half the title of the song "Interstellar Overdrive"on the first Pink Floyd album 'Piper at the gates of dawn'
20 exactly
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A system of sun and planetary gears operated by an electrical switch, giving extra gear ratios in 3rd and 4th.
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Additional gearbox, mechanically or electrically operated, giving a step-up ratio on 4th or sometimes lower gears, even reverse on LandRovers. (20 words)
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My dad had overdrive on his Wolseley 6/110. A sort of toggle thing . Looked a like an extra choke control. ( 20 words )
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Switch on mates triumph dolomite gearstick that gave him electric shocks and put HIM into overdrive....
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Humph, it was a small "T" handle on the 6/110, and said "Push for overdrive" on it. There was also a "kick down" switch under the throttle pedal, this dropped out the overdrive so you could rev a bit faster for overtaking etc. the big Wolseley was one of my favourite cars during apprentice days in the 60's.
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Interesting so far (apart from the musical references). According to what I remember from dad's aged tome "Motor Car Design" with a broken spine and yellowed pages, overdrive gear is one that allows a cruising speed to be maintained for fewer engine revs. No surprises so far but the key point was that because the engine turns slower and therefore can't reach maximum power before friction and air resistance overcome it, maximum speed for that vehicle could only be reached in a lower gear.
Overdrive; any gear that is too high to allow the engine in the vehicle to develop maximum power. 17 words.
What do you think ?
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That sounds pretty correct to me. I had an Opel Monza auto with 3 speeds and an overdrive top. I couldn't pull up motorway gradients in overdrive and had to kick down to 3rd, but then it revved too high. There was too big a gap between 3rd and 4th.
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>> Overdrive; any gear that is too high to allow the engine in the vehicle to develop maximum power. 17 words. What do you think ?
cjehuk has it above, top gear ratios were historically 1:1, "Overdrive" defined a ratio that was higher than 1:1.
Of course the actual engine to road speed ratio was also defined by the final drive ratio, wheel size and tyre profile.
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overdrive : to hit a golf ball too hard :)
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Further explanation of o/d operation. The switch operated an electrically operated valve in the o/d gearbox such that the internal oil pump generated approx. 400 psi to push the internal double cone clutch from 'normal' to 'o/d' position bringing those planet gears into operation. O/d operation gave much more relaxed cruising at 70+ in my Dolomite 1850. But if it got stuck in o/d you couldn't reverse the car......
Sorry for exceeeding the word limit.
All the best for 2010!
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>>Overdrive; any gear that is too high to allow the engine in the vehicle to develop maximum power. 17 words
Hawkeye you have answered your own question I think.
The only other sense I think in which in might be technically be used, in relation to a gearbox, is where there is a direct drive or 1:1 gear, and a higher gear 'overdrive' gear is provided, sometimes by an add-on gearbox. If a separate box is used, then it can also be used as a 'splitter' for the two top gears.
Incidentally, the 4 speed auto on my 2002 CRV would only use 3 gears unless a button on the end of the lever marked "O/D" was pressed. Sure enough, top speed was reached only in third, so that complied with Hawkeye's definition above. Whether 3rd was 1:1 at the gearbox I can't recall - I suspect not - but it's academic really given the use of a final drive reduction gear.
EDIT - just noticed Cheddar also referred to this usage.
Edited by Manatee on 31/12/2009 at 17:40
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