Re: [DML] Re: Speedo gear rpm.
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Re: [DML] Re: Speedo gear rpm.



Hello

Believe it or not, but our cars are metric. This means that the speedo is 
calibrated for 1 m = 1 turn. This gives us 100km/h = 1000rpm. This explains 
why your speedo was off by 2mph... 100km/h is 62mph ;)
The angle drive has the gears at such a ratio that for every one meter 
traveled the cable makes one revolution.

Hope this helps

Tom Niemczewski
vin 6149 (in Poland!)
Google earth: 52°25'17.30"N 21° 1'58.00"E
dmctom@xxxxxxxxx
www.deloreana.com

----- Original Message ----- 
From: "Elvis" <elvisnocita@xxxxxx>
To: <dmcnews@xxxxxxxxxxxxxxx>
Sent: Monday, May 05, 2008 1:29 PM
Subject: [DML] Re: Speedo gear rpm.


>
> I love the DMCNEWS.com website, some years ago I found
> a great information there....which said 60mph = 1000rpm....
>
> yesterday we swapped speedos and my self calibrated speedo
> which shows 60mph @ 1000rpm was only 1-2 mph off compared
> to GPS !
>
>
>
>
>
> --- In dmcnews@xxxxxxxxxxxxxxx, Joe Angell <jangell@...> wrote:
>>
>>
>> I don't know what it is officially, but I did the math out and got
>> ~2030 RPM @ 85 MPH.  I'm assuming that one turn of the tire is
> equal
>> to one turn of the speedometer cable, but I'm not entirely sure if
>> that's the case (there might be some kind of gearing at the angle
>> drive that I don't know about; I'd appreciate it if someone could
>> confirm this):
>>
>> Here's the math, based on the diameter of the front tire:
>>
>> Tire Circumference:        43.98" = 14" diameter tire * pi
>> Tire Revolutions per Mile: 1440   = 63360" per mile / 43.98"
>> Miles per minute @ 85 MPH: 1.41   = 85 miles per hour / 60
> minutes
>> per hour
>> RPM of front tire:         2030   = 1440 * 1.41
>>
>> You can get the RPMs at any speed with this formula:
>>
>> RPM = (MPH / 60) * 1440
>>
>> Obviously this value will vary based on the amount of air in your
>> tires at any given time, but hey.
>>
>> -- Joe
>>
>> > Does anyone know what RPM the speedo cable operates at?
>> >
>> > Bob

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