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Maximum Reverse Speeds.


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#1 Manic Moran

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Posted 05 July 2012 - 2048 PM

Wondering where to find a list of maximum speeds in reverse for varous tanks. Almost every source has max speed forward, but reverse is more complicated.

The simple way seems to be to take the maximum speed, and multiply/divide by gear ratios, on the basis that top speed is ultimately governed by a redline. eg M4A3 does 26mph in top gear, so multiply by 4th gear ratio (0.73) and divide by reverse gear ratio (5.65) to get about 4mph top speed in reverse. Of course, this assumes that top speed forward is limited by the redline / engine governor, which is by no means certain.

#2 Colin

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Posted 05 July 2012 - 2359 PM

You could get Tim to test the theory on his M5

#3 Old Tanker

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Posted 06 July 2012 - 0044 AM

I always thought it was the same as low gear forward which was 9 MPH on the M-48s.

Since the speedometers don't register reverse speed you would have to a companion vehicle next to you to clock your speed in reverse as they drive forward side by side.

#4 Max H

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Posted 06 July 2012 - 0442 AM

Wondering where to find a list of maximum speeds in reverse for varous tanks. Almost every source has max speed forward, but reverse is more complicated.

The simple way seems to be to take the maximum speed, and multiply/divide by gear ratios, on the basis that top speed is ultimately governed by a redline. eg M4A3 does 26mph in top gear, so multiply by 4th gear ratio (0.73) and divide by reverse gear ratio (5.65) to get about 4mph top speed in reverse. Of course, this assumes that top speed forward is limited by the redline / engine governor, which is by no means certain.


I think you'd be better off comparing the difference between first gear ratio & top speed in that gear and reverse gear ratio - at high speed in top gear, wouldn't friction from moving parts be much higher, so it might not be redlining at top speed

I always thought it was the same as low gear forward which was 9 MPH on the M-48s.

Since the speedometers don't register reverse speed you would have to a companion vehicle next to you to clock your speed in reverse as they drive forward side by side.


Some reverse gears are lower than first. Measuring gets rather impractical when you need to clock the speed of, say, a maus. And why not just use a GPS receiver as a more accurate speedo that doesn't need co-ordination between 2 vehicles?

#5 Manic Moran

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Posted 06 July 2012 - 1057 AM

I think you'd be better off comparing the difference between first gear ratio & top speed in that gear and reverse gear ratio - at high speed in top gear, wouldn't friction from moving parts be much higher, so it might not be redlining at top speed


That's my worry, but 'top spead at first gear' isn't commonly advertised either. Sometimes the TM has it.

#6 istvan47

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Posted 06 July 2012 - 1309 PM

AFAIK, the M2 Bradley was criticized in mobility during DS as, in reverse, it could go up to 11 kmh, while the M1 Abrams was capabel of 32 kmh(!).

Tactical vs tactical, the M2 was however always with a lot of fuel reserve (atleast 50%) when M1s needed to be refuelled (with a lot of fuel, also: the documents available around 20 years ago talked about 16 l/km as average, of course the war is not the same thing of a theorical driving test, especially as the M1 lacked an APU, or atleast, it was not standardized on all the tanks).

Edited by istvan47, 06 July 2012 - 1320 PM.


#7 Kensuke

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Posted 06 July 2012 - 1601 PM

The Type 10 is easy. 70km/h max speed. Forward and reverse. CVT transmission. No gears.

Probably handy for those times you simply have to get the fuck out of Godzilla's way.

#8 Arminius

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Posted 06 July 2012 - 1610 PM

I was always impressed with the German Rec Vehicles :

with a reverse driver they could go backwards as speedy as forward.

The 8 wheeled WW II Vehicles ( SDKfZ 234 Series ) as well as the Luchs ( an expensive vehicle )

Hermann

#9 Ssnake

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Posted 06 July 2012 - 1840 PM

IFV Marder has a theoretical max reverse speed of 65km/h, but as it can't even reach that velocity while going forward (having grown overweight with the various uparmoring programs) about 30...35 is probably realistic. Same as Leopard 2 (where the theoretical and practical limits are the same).

#10 rmgill

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Posted 06 July 2012 - 1914 PM

For tracked vehcicles, I'll bet that the Stridsvagn 103 has the best reverse speed given the layout and the crew setup with the wireless operator/rear facing driver.

For wheeled vehicles, it'd probably be a race between the spahpanzer luchs and the WWII Daimler Dingo.

The dingo had a 55mph forward speed with a wilson self changing gearbox. Reverse was accomplished through a transfer box. The Luchs has the advantage of the rear facing driver/RTelo and more modern power plant. The Luchs probably has the reverse speed advantage with a driveline designed to go that fast in reverse.

#11 Kensuke

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Posted 06 July 2012 - 2033 PM

IFV Marder has a theoretical max reverse speed of 65km/h, but as it can't even reach that velocity while going forward (having grown overweight with the various uparmoring programs) about 30...35 is probably realistic. Same as Leopard 2 (where the theoretical and practical limits are the same).


The Leo 2 must have a really tall second reverse gear since, like most modern MBTs, it only has two.

This kinda begs the question if it's ever necessary for a tank to back up that fast.

#12 TTK Ciar

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Posted 06 July 2012 - 2252 PM

And why not just use a GPS receiver as a more accurate speedo that doesn't need co-ordination between 2 vehicles?


Stopwatch and two landmarks a known distance apart also works. When you're talking about speeds on the order of 15 feet per second, they don't need to be very far apart to get decent accuracy.

#13 Froggy

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Posted 07 July 2012 - 0311 AM

AMX30B2: 65km/h forward and reverse (inverter).
Leclerc: 72km/h forward and 38km/h in reverse (2 reverse gears).

#14 DougRichards

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Posted 07 July 2012 - 0326 AM


IFV Marder has a theoretical max reverse speed of 65km/h, but as it can't even reach that velocity while going forward (having grown overweight with the various uparmoring programs) about 30...35 is probably realistic. Same as Leopard 2 (where the theoretical and practical limits are the same).


The Leo 2 must have a really tall second reverse gear since, like most modern MBTs, it only has two.

This kinda begs the question if it's ever necessary for a tank to back up that fast.


there was an old joke, at least 60 years old, about a certain country that shall remain nameless whose tanks in WW2 had three reverse gears, and one forward gear in case of sneak attack from behind.....

#15 JW Collins

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Posted 07 July 2012 - 0542 AM

AMX30B2: 65km/h forward and reverse (inverter).


Jokes regarding France aside, was this a design requirement? I'm not familar with French armored strategy during the Cold War, but I see how such a feature could be useful against Warsaw Pact forces.

#16 shep854

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Posted 07 July 2012 - 0859 AM

Considering the friends of the people you just killed are likely to be quite annoyed (and lethal), the quicker you can be someplace else, the better--even when it's just to get another shot. With practical back-up cams for drivers, a fast reverse speed can be better utilized tactically.

This reminds me of King of the Killing Fields, where XM1 drivers realized that they could instantly go from forward to reverse with a flick of the wrist, which measurably reduced the time the tank was exposed when it unmasked to fire. The only problem was that this practice trashed transmissions. Engineers 'solved' the problem by modifying the system so that the tank had to come to a complete stop before reverse could be selected--which of course slowed the tank's ability to quickly back to cover

#17 Ivanhoe

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Posted 07 July 2012 - 1939 PM

Don't forget to consider incline capability. It would really suck to descend a 20 degree or whatever grade, encounter an obstacle, minefield, or whatever, and have too tall of a reverse gear to be able to reverse back up the hill. Might also impact the ability of one AFV to yank another out of a bog. If an armored column loses the point man into a bog, it would be a lot easier if the #2 vehicle could merely hook up and pull the #1 vehicle rearward without having to turn around and work via backup cam.

#18 dejawolf

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Posted 20 July 2012 - 0643 AM


IFV Marder has a theoretical max reverse speed of 65km/h, but as it can't even reach that velocity while going forward (having grown overweight with the various uparmoring programs) about 30...35 is probably realistic. Same as Leopard 2 (where the theoretical and practical limits are the same).


The Leo 2 must have a really tall second reverse gear since, like most modern MBTs, it only has two.

This kinda begs the question if it's ever necessary for a tank to back up that fast.


can't really speak from life experience, but at least in SB pro PE, the fact the T-72 only has a 4kph reverse gear is a serious drawback that severely limits your tactical options.
for example it's more or less impossible to take up efficient battle positions in the defense.
it also means that anything you do you have to commit fully to, because there is no turning back.

#19 dejawolf

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Posted 20 July 2012 - 0655 AM

Wondering where to find a list of maximum speeds in reverse for varous tanks. Almost every source has max speed forward, but reverse is more complicated.

The simple way seems to be to take the maximum speed, and multiply/divide by gear ratios, on the basis that top speed is ultimately governed by a redline. eg M4A3 does 26mph in top gear, so multiply by 4th gear ratio (0.73) and divide by reverse gear ratio (5.65) to get about 4mph top speed in reverse. Of course, this assumes that top speed forward is limited by the redline / engine governor, which is by no means certain.


gears for T-72A (kph/h):

1st: 7.32
2nd: 13.59
3rd: 17.16
4th: 21.47
5th: 29.51
6th: 40.81
7th: 60
reverse: 4.18

gears for T-80 (kph/h):

1st: 15.6
2nd: 31.6
3rd: 47.0
4th: 68.5
reverse: 10.8

BMP-1 (kph/h)
high-gear:

1st: 10,6
2nd: 19,6
3rd: 29,1
4th: 43,3
5th: 65
reverse: 10,6


low-gear:
1st: 7,3
2nd: 13,6
3rd: 22
4th: 30
5th: 45
reverse: 7,3

Edited by dejawolf, 20 July 2012 - 0709 AM.


#20 DKTanker

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Posted 20 July 2012 - 1034 AM

I always thought it was the same as low gear forward which was 9 MPH on the M-48s.

I believe that is correct for the M48A3-M60A3. Selecting reverse just reversed the direction of low range giving them a theoretical reverse speed of 9 mph. The M1 does the same for 1st and 2nd gears giving it a 20 mph reverse speed.




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