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TR2/3/3A Speedometer is off by 10 mph??

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I've been running the Classic Speed gps mod for about 18 mos and several thousand miles in my TR6. My original problem with speedometer accuracy was similar to the OP's....at 70 mph indicated I was actually travelling 81 mph while at 40 mph indicated, the error was only 7 mph, i.e., I was actually travelling 47 mph. With the installation of the Classic Speed, my maximum error is -3 mph at an indicated speed of 70 mph. In other words, when the speedo says 70 mph I'm actually travelling 67 mph. Between 35 and 55 mph, the speedo is spot on. Certainly acceptable for me.

I have not encountered any gps drops while travelling under long overpasses, alleys or on roadways covered by overhead foliage. One place I have not tried is in a tunnel, although the software in the Classic Speed is supposed to maintain the gps readouts when driving in tunnels.

Installation is easy. For me, they hardest part was removing the original speedometer cable from the gearbox connection. If the thought of removing the speedometer and either sending it out for a recal or fiddling with it yourself is too daunting, the Classic Speed is a great alternative.
 
To clarify, this is a never seen before, patent device that drives your original mechanical speedometer regardless of any changes made to the vehicle (tires, transmission, etc). GPS tech has come a long way since my days in aerospace R&D years ago. I've programmed solutions to the various scenarios mentioned and it's much less susceptible to dropping signal than your cell phone (or other hand-held GPS) as it uses an active remote antenna. It's used in any make / model, in any country, and makes your classic complete.
 
So what aspect, exactly, is patented? Just the fact that it drives an old mechanical speedometer head instead of electric?
https://www.summitracing.com/parts/izl-s9020

What's the patent number?

And perhaps you could explain exactly how it compensates for old, worn speedometer heads that are non-linear, and the trip meter/odometer readings no longer match the speedometer?

Or for when the only signal path is no longer a straight line to the satellite (like in a tunnel or in a narrow alley). Your web site already describes (kudos to you) how it fakes the speed reading when it can't track enough signals. Of course there is no indication to the driver as to when you are displaying how fast he was going a minute ago instead of now.

We used to do a torture test that revealed how much our competitors concealed information like that. Had a little train track setup, with a long straight and a 90 degree turn at the end. Get the unit rolling along the straight at a constant speed, then clap a cookie tin over the antenna just before the curve. Almost every unit we tested would swear it was sailing along in a straight line, even after the car was stopped.

Then there's the potential for someone to be deliberately distorting the GPS signals. I couldn't find a link just now, but there was an article published a few years ago where some college kids were permanently disabling high end commercial GPS units just by letting them collect a bogus almanac. This article only talks about jamming (preventing the reception of GPS), but spoofing (causing the unit to get a false result) is also fairly easy and often done. One of the US drones was stolen by spoofing it's GPS receiver, so it thought it had gone "home" instead of into enemy territory.
https://www.theguardian.com/technology/2010/feb/22/car-thieves-using-gps-jammers
 
An industrial GPS speedometer I know of reverts to a backup inertial system to keep the display relatively accurate during GPS lapses.

Ed
 
All great questions Randall! First, let me stand corrected - Patent Pending. U.S. Patent Application No. 15/044,791 entitled SPEEDOMETER DRIVE SYSTEM AND METHOD
And yes, this patent covers the driving of a mechanical speedometer via GPS technology. The link you sent was for driving an electronic speedo as you said. My intention was keep the original speedometer to the car, or at least the correct speedo to the YMM.

As you have indicated, the mechanical speedo is prone to issues. We stress the need for the speedo to be in good working order, but honestly, the majority of issues we've seen with needle bounce and non-linearity stem from bad speedo cables. We have a great source for those, made to much better quality that you generally find from distributors.

As for jamming, yes I recall this was an issue years ago but technology has come a long way in just a couple of years. We are using a pretty standard GPS chip with anti-jamming technology, supporting 210 PRN channels with 66 search and 22 simultaneous tracking channels. I agree, the external antenna does need a fairly good view of the sky but my testing, and our beta testers, have found it to work very well under fiberglass and canvas, as well as under seats and tucked behind bumper over-ridders . Of course, the better view it has of the sky the better signal it receives.

Admittedly, this is not warmly received by everyone, but for those who have been looking for a solution like this for years (as I had been), Classic Speed is it. As @arcom says, it works extremely well, is easy to install and set up. Thanks BTW! ;-)

I really don't want to turn this in to a defensive rant. I simply wanted to let members know Classic Speed exists and they have this option. We starting shipping in July 2016 and our sales are going very well. We have great interest from magazines and well known members of the classic car space, and hope to grow this to a well recognized product.

Thanks for the great engagement!
 
TR3driver said:
Been around for quite awhile. I guess you don't really need to know how fast you're going in areas without decent GPS coverage, like tunnels, parking garages and narrow alleys. But it would make me crazy, just wondering every time I looked at it whether it was being affected by multipath or poor DOPs. (I used to help write GPS receivers, so I'm rather uncomfortably aware of how many different ways they can go wrong, and how poorly written most cheap receivers are.)
Click to expand...

But a free speedometer download to my IPhone does make checking the speedo a lot easier than a following car or trying to hold a speed for a roadside radar sign to give a readout.
Tom
 
Hmm, I wonder if there would be a market for a similar device, that could be calibrated to compensate for non-linearities in the speedo head? It would be easy enough to build, with the plethora of tiny embedded processors on the market today. The hard part (for me) would be a smart phone interface (instead of physical pushbuttons) for entering all the calibration constants, but even that looks easy enough.

Of course, the odometer/trip meter would still be off by however badly the speedometer is off (which is also a problem with the product above); but maybe most would be more interested in accurate speed rather than accurate distance?
 
Neat patent...but it seems to be about 2 decades late, in that it's been that long since a cable has been used on a car or boat. All its got is the resto-mod market, and pricing for a small market might be a problem.
 
If Miky is back (that was funny John) if you look close at the speedo head in the glass you will see a very small white dot down by the zero. The dot is there for the preload on the needle; there is this small amount tension on the needle so it does not flop around. When the need is removed then reinstallation it goes on that dot past the zero. Once on the dot, then you carefully move the needle back to the stop post. At least that is what I was told by the old owners of MO MO. Another way is to drive at a set speed and push the needle back on. I like the GPS speed idea for speed plus I bet a real speedo shop as some equipment to calibrate it correctly.


The way I do it is trial and error with the white dot. If I need more speed I do not go all the way to the white dot when I reinstall. Like Randall said be delicate with the needle, but sometimes you have to pull pretty hard to get it off; back in the day they were a lot of speedos around so I did not worry so much about damaging one either. Another trick is when the glass is off take a very fine dry artists brush and dust of the dial and be careful of oily dirt on your hands because the flat black dial just sucks it right up.
steve
 
The white dot and the GPS alternative both depend on the hair spring and magnets being at their original strength.

As either the magnets or the spring weaken the speedo reads high and the error is non-linear so the solution becomes more complex - repositioning the spring attachment &/or modifying the power of the magnets. Both are doable by the brave and crafty though many just move the needle to get 45 mph about right and live with a mental adjustment for the rest.
 
TR3driver said:
Well, I thought so, but the Wikipedia article only says "including Jaguar, Aston Martin, Ferrari, Austin-Healey, Jensen, Bristol, AC, Armstrong Siddeley". Of course, it also says that TR6 quit using them at the end of 69, which isn't correct.

But apparently the early Volvos only got D-types, later followed by LH, J and P. Sorry about that.
Click to expand...

You were right in the first place. I have an A-type from New Zealand which is believed to be from a Volvo. I checked Wiki which includes Volvo:

"In Europe[edit]

The vast majority of overdrives in European cars were invented and developed by a man called de Normanville and manufactured by an Englishcompany called Laycock Engineering (later GKN Laycock), at its Little London Road site in Sheffield. The system was devised by Captain Edgar J de Normanville (1882–1968),[SUP][2][/SUP] and made by Laycock through a chance meeting with a Laycock Products Engineer. De Normanville overdrives were found in vehicles manufactured by Standard-Triumph, who were first, followed by Ford, BMC and British Leyland, Jaguar, Rootes Group and Volvo to name only a few. Another British company, the former aircraft builder Fairey, built a successful all-mechanical unit for the Land Rover, which is still in production in America today."
 
My first car was 1954 Ford Victoria with overdrive. I did not give that car the love it deserved because it was very clean and straight and I just thought OK it will due.
 
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