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Author Topic: instrument location on motorcycle, M/PG  (Read 736 times)
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speedrattle
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« on: September 06, 2018, 04:55:48 PM »

hey folks

i've been running an old triumph 650 in modified production at ECTA and LTA for several years now. in 2020 i'm planning on taking it to BNI. i have a question on SCTA rules interpretation for the modified class, 7.F.11:

Quote
Motorcycles using non-OEM instruments, or OEM instruments not using OEM mounts, must be mounted within an area defined as no farther forward than 6 inches in front of the leading edge of the upper triple clamp nor more than 4 inches above the top of the upper triple clamp nor more than 2 inches below the top of the upper triple clamp nor wider than 1 inch outside of each fork tube.

on my machine the riding position puts my field of view to the left of the tanks, below the top triple clamp and above the bottom triple clamp:



in order to be able to see my tach, i mount it right in the center, level with my face. when i do this, the centerline of the tach falls below the point not more than 2 inches below the top of the upper triple clamp . . .



however, significant portions of the mounted instrument are contained above the point 2 inches below the top of the upper triple clamp:



there isn't anywhere else to put it that will allow me to see the tach during a run, so my options are to leave it where it is, or run without a tach.

question: what is the intent of the rule? does my instrument position comply?
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mergatroyd
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« Reply #1 on: September 06, 2018, 11:52:57 PM »

I have taken this to mean that any dimensions that exceed those listed are not legal. The intent (as I understand it, as just some guy) is to limit drag reducing opportunities.
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Lemming Motors
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« Reply #2 on: September 07, 2018, 03:05:47 AM »

What about a 2.1/16" digital tacho with shift light?
Single wire to the coil and small enough to mount elsewhere?
Speedhut.com have a sort of trad one with white on black face though that can be customised; GR2-TACH-02 or similar.
I would mount it to the vertical upright (don't know what that's called on a bike - steering head?) between the triple clamps on the inside (i.e. tank side) if it doesn't get caught out by the steering angle which I assume is minimal if you are only going in a straight line?

No association with Speedhut; just aware of their range as I was rootling around on the site for a speedo and tacho for the Lakester build and they were super helpful- I couldn't find anything suitable in the UK but will be in California in October for work so hopefully they will be built by then.

You could mock it up with a piece of wood and see if it fits / interferes - less drag than the current one too (okay, that's probably not true).

John
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speedrattle
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« Reply #3 on: September 07, 2018, 01:50:48 PM »

I have taken this to mean that any dimensions that exceed those listed are not legal. The intent (as I understand it, as just some guy) is to limit drag reducing opportunities.

i didn't think of it that way. if that's the way the rule is to be interpreted, there's no point in running a tach at all, because the only time it would be visible is idling at the start line.
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speedrattle
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« Reply #4 on: September 07, 2018, 02:03:46 PM »


Single wire to the coil and small enough to mount elsewhere?
Speedhut.com have a sort of trad one with white on black face though that can be customised; GR2-TACH-02 or similar.


i'm running a magneto ignition without a battery, at the moment, so i can't fit any electrical systems to the bike. i do have a 3.5-inch speedhut tach for it already, though, if i switch to a battery-coil ignition system, but the mounting question would be the same. 

Quote
I would mount it to the vertical upright (don't know what that's called on a bike - steering head?) between the triple clamps on the inside (i.e. tank side) if it doesn't get caught out by the steering angle which I assume is minimal if you are only going in a straight line? . . . What about a 2.1/16" digital tacho with shift light?

that might be doable. interestingly, the rules specify upper, lower, and forward limits of the space available for the tach, but don't say anything about how far to the rear it can be.
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Mangold
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« Reply #5 on: December 02, 2018, 06:50:02 PM »

The rule stating that instruments have to be mounted "within an area defined as..." i've interpreted it to mean the instrument needs to be entirely within that area.  Would love to see it interpreted by officials differently, or redefined if this is the correct interpretation.  My tach sticks up higher than I'd like, but that doesn't mean it can't be seen in a riding position, just that I can't see it in my preferred riding position.
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wobblywalrus
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« Reply #6 on: December 02, 2018, 10:47:59 PM »

The rev limiter is set at the shift point rpm on my Triumph.  It is also the highest rpm that I want the engine to run.  This way, shifting is done when the rev limiter kicks in and there is no need for a tach.
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