Why do antique auto tachs do this?
I have looked at a bunch of websites with no luck. But someone here is
sure to know. All the mechanical tachs I am familiar with work the same, with an eddy current disc and a spinning magnet. I figured this out when I fixed a speedometer in a VW Bug way back in 1980. But I have seen several antique race cars with tachs that don't seem to work this way because the needle moves in a jerky fashion. It will swing fast to a position and then stop. The rpm will then audibly change and there will be a time lag before the needle quickly swings to another position and stops dead. It's as if the needle can only move in discrete steps. I can't figure out why this is, if it's done on purpose, or if it's desirable. I have seen this type of action on several different makes of race cars. So, who here knows about this? If you want to see this in action search Youtube for the TV show "Victory By Design". If you like cars at all, and race cars in particular, and have never seen any of these shows then by all means look it up. A retired race car driver, Alain de Cadenet, does a wonderful job driving and showing off the cars. His obvious joy driving the cars and his obvious skill driving the cars makes for a really enternaining show. He talks about brakes, engines, suspensions, frames, superchargers, carbs, etc. But he never says anything about the tachs. Eric |
Why do antique auto tachs do this?
On Monday, January 30, 2017 at 6:00:50 PM UTC-5, wrote:
I have looked at a bunch of websites with no luck. But someone here is sure to know. All the mechanical tachs I am familiar with work the same, with an eddy current disc and a spinning magnet. I figured this out when I fixed a speedometer in a VW Bug way back in 1980. But I have seen several antique race cars with tachs that don't seem to work this way because the needle moves in a jerky fashion. It will swing fast to a position and then stop. The rpm will then audibly change and there will be a time lag before the needle quickly swings to another position and stops dead. It's as if the needle can only move in discrete steps. I can't figure out why this is, if it's done on purpose, or if it's desirable. I have seen this type of action on several different makes of race cars. So, who here knows about this? If you want to see this in action search Youtube for the TV show "Victory By Design". If you like cars at all, and race cars in particular, and have never seen any of these shows then by all means look it up. A retired race car driver, Alain de Cadenet, does a wonderful job driving and showing off the cars. His obvious joy driving the cars and his obvious skill driving the cars makes for a really enternaining show. He talks about brakes, engines, suspensions, frames, superchargers, carbs, etc. But he never says anything about the tachs. Eric I don't really know about what you're talking about, but really old tachometers had centrifugal weights and displaced according to the force on the weights. I started sports car racing in 1966, and my first tach was a Sun Tach that was all-electronic and very smooth -- aftermarket, on my John Fitch Corvair. -- Ed Huntress |
Why do antique auto tachs do this?
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Why do antique auto tachs do this?
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Why do antique auto tachs do this?
On Tuesday, January 31, 2017 at 1:08:32 AM UTC-5, Bob Engelhardt wrote:
On 1/30/2017 6:12 PM, wrote: I don't really know about what you're talking about, but really old tachometers had centrifugal weights and displaced according to the force on the weights. ... 3:16 here https://www.youtube.com/watch?v=VMP7fW7tj3w Oh, man, what a cool car. I don't know how that one passed me by -- or maybe it didn't and I just forgot about it. In 1966, the only things I cared about were girls and sports car racing. Thanks, Bob. -- Ed Huntress |
Why do antique auto tachs do this?
On Tuesday, January 31, 2017 at 1:08:32 AM UTC-5, Bob Engelhardt wrote:
On 1/30/2017 6:12 PM, wrote: I don't really know about what you're talking about, but really old tachometers had centrifugal weights and displaced according to the force on the weights. ... 3:16 here https://www.youtube.com/watch?v=VMP7fW7tj3w BTW, I caught that jerking tach. I just got caught up in the car. g -- Ed Huntress |
Why do antique auto tachs do this?
On Tue, 31 Jan 2017 08:45:10 +0700, John B.
wrote: On Mon, 30 Jan 2017 15:05:47 -0800, wrote: I have looked at a bunch of websites with no luck. But someone here is sure to know. All the mechanical tachs I am familiar with work the same, with an eddy current disc and a spinning magnet. I figured this out when I fixed a speedometer in a VW Bug way back in 1980. But I have seen several antique race cars with tachs that don't seem to work this way because the needle moves in a jerky fashion. It will swing fast to a position and then stop. The rpm will then audibly change and there will be a time lag before the needle quickly swings to another position and stops dead. It's as if the needle can only move in discrete steps. I can't figure out why this is, if it's done on purpose, or if it's desirable. I have seen this type of action on several different makes of race cars. So, who here knows about this? If you want to see this in action search Youtube for the TV show "Victory By Design". If you like cars at all, and race cars in particular, and have never seen any of these shows then by all means look it up. A retired race car driver, Alain de Cadenet, does a wonderful job driving and showing off the cars. His obvious joy driving the cars and his obvious skill driving the cars makes for a really enternaining show. He talks about brakes, engines, suspensions, frames, superchargers, carbs, etc. But he never says anything about the tachs. Eric I believe that you are talking about a Cronometric tachometer. Smith's cronometric speedometers and tachometers were common on both automobiles and motorcycles at one time. See http://tinyurl.com/h6n8m47 for some details. Greetings John, That's it! Thanks! I went to that site already but only saw the eddy current type. It has bugged me for a long time why the jerky motion tachs were used and no I know. Cool. Thanks again, Eric |
Why do antique auto tachs do this?
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Why do antique auto tachs do this?
On Wednesday, February 1, 2017 at 9:56:23 AM UTC-5, Bob Engelhardt wrote:
On 1/31/2017 1:22 AM, wrote: BTW, I caught that jerking tach. I just got caught up in the car. g Ha! Me too - I went to YouTube for the "Victory By Design" that Eric referenced, saw the Jag, and got lost down a rabbit hole. Like you, I don't know how I missed that back in '66, but career had displaced cars, I guess. I'm glad that Eric didn't get us started on that series before I retired, or during trout season. I know now where I'm going to be spending some spare time this month. Many of those are cars I've always loved and those videos get my heart racing. -- Ed Huntress |
Why do antique auto tachs do this?
On 01/30/2017 06:12 PM, wrote:
On Monday, January 30, 2017 at 6:00:50 PM UTC-5, wrote: I have looked at a bunch of websites with no luck. But someone here is sure to know. All the mechanical tachs I am familiar with work the same, with an eddy current disc and a spinning magnet. I figured this out when I fixed a speedometer in a VW Bug way back in 1980. But I have seen several antique race cars with tachs that don't seem to work this way because the needle moves in a jerky fashion. It will swing fast to a position and then stop. The rpm will then audibly change and there will be a time lag before the needle quickly swings to another position and stops dead. It's as if the needle can only move in discrete steps. I can't figure out why this is, if it's done on purpose, or if it's desirable. I have seen this type of action on several different makes of race cars. So, who here knows about this? If you want to see this in action search Youtube for the TV show "Victory By Design". If you like cars at all, and race cars in particular, and have never seen any of these shows then by all means look it up. A retired race car driver, Alain de Cadenet, does a wonderful job driving and showing off the cars. His obvious joy driving the cars and his obvious skill driving the cars makes for a really enternaining show. He talks about brakes, engines, suspensions, frames, superchargers, carbs, etc. But he never says anything about the tachs. Eric I don't really know about what you're talking about, but really old tachometers had centrifugal weights and displaced according to the force on the weights. I started sports car racing in 1966, and my first tach was a Sun Tach that was all-electronic and very smooth -- aftermarket, on my John Fitch Corvair. The OP is describing a chronometric tachometer. I had a Royal Enfield and an Atlas that had them. http://www.mg-tc.de/articles/JaegerC...struments.html http://www.chronometrics.co.uk/Tacho...chometers.html |
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