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MG Midget and Sprite General - Wireless cycle computer for car use (NMC)

Does anyone have good experience of using a wireless bike 'computer' for accurate speed readout in a car? Where to position sensor and how to fix etc.
Specifically; I am setting up as an independent ADI driving instructor, and will be using a car that, because of the dash shrouding, has a speedo that's impossible to read from the instructor's seat.
I thought wireless might be the way to go for ease of installation, but not sure if 'range' would be adequate, so would consider a 'wired' one.
Thoughts, please!

Steve
Steve Clark

why not use the speed screen on a SatNav?
N Atkins

My wired one uses a bracket hanging off the spring mounting platform near to a Araldited on magnet on the brake drum outer

The wire follows the axle, then runs at the top of the axle arch into the car via a hole near the pump wiring

The small hole that the pump wiring goes in with is a tad small for three wires to use

I cut the short wire that comes with the kit and extended the wires with thin speaker cable to the inner wire and the co-axial outer

same at the dash end too

My Sigma cost me about twelve quid

It is very accurate too, we have several roadside Nags near here "You are doing thirty one miles an hour" on a LED screen

My cycle speedo always tallys with the sign boards
Bill 1

hmph Bill's is almost exactly the same as mine :p

Sigma BC1600L is the computer part, mine uses a bracket joined to the very edge of the drum backplate with the magnet araldited to the drum..

then there's some speaker cable, though mine's not posh coax, just twin wires. Made my own hole in the rear 'floor' and araldited the wire into it with enough slack so the rear axle can go up and down.

mine was only 9 quid :p It's clipped into the old gearbox hole, lovely and accurate and goes up to and over 100 mph, unlike the last 4.99 tesco job. Commented on by my sanguine MOT man, but just 'cos he wanted to know what it was, he seemed happy with it. It's very useful as the main speedo is currently not working. Brill for mpg and average speed things.
Rob Armstrong

Hell of a bike rider to get over the ton,

I haven't used the wireless one, but if it's anything like my heart rate monitor it's not that reliable and affected by other radio signals. For instance while running on the treadmill, my heart rate can register on the one alongside which gives the incumbent a scare! Imagine you suddenly read the speed for the bike alongside you.

Stick to the wired one then you won't get interference from passing cyclists, your car radio, telephones etc. Also battery life is inconsistent.

Max max-at-midgetmax-dot-com

GPS speedos not accurate when doing sharp turns (e.g. roundabouts) and on steep gradients; in both cases they read low.

Does anyone know if they are accepted by the law as a substitute for a normal speedo?

A
Anthony Cutler

I don't think that they are Anthony - at least,they don't count for the MOT, and that's the usual staple for the police to start whinging at!

Suppose you can take the "it just happened a few minutes ago" argument .....
rachmacb

I didn't know that a working speedo was mandatory, I just thought that it was an offence to exheed the speed limit.
I use the sat nav.
Gary & Gaps

Steve

Mine was similar to Bill's , sensor was mounted on the rear brake back plate, and a magnet bonded to the brake drum. It worked well until the magnet decided to part company with the brake drum.

But anyway now I use an old Sat Nav for a speedo as Nigel suggests, although not as discreet as the cycle speedo it has other adavantages.

Ian
Ian Webb '73 GAN5

Road Vehicles (Con and Use) Regs 1986

Reg 35(2) (h) permits the use alone of a Tachometer (The Spy in the Cab) instead of a speedo providing it is marked with the Approval Mark and complies with the Community Recording Equipment Regs.

Until such time as it is fitted then a Speedo is required and which must be maintained in good working Order.

Journeys with a defective speedo are permitted when the defect occurred during the current journey, or as a result of the defect it has ceased to be in good working order and steps have been taken to have the vehicle equipped with all reasonable expedition, by means of repair or replacement, with an instrument which is in good working order. (Reg 36 (2))

Sadly, speeding is also illegal :P
rachmacb

I've not used a SatNav for at least 6/7 years but even then I think the refresh rate was only about 3 seconds

I'm guessing, don't know and not researched it but the SatNav would probably be more accurate than even modern speedos, my Midget speedo used to be more accurate that my wife's car new car until I had the g/box changed

as my mate's speedo was away for 6 weeks being repaired and he wanted an MOT he checked and told me you must have a speedo with 30 mph marked on it - but he's not the best at getting accurate details, no mention of accuracy either
N Atkins

Rach you meant tachograph not tachometer, very different!
David Smith

yet again I was typing as rach was posting so my last post was already outdated

and yet again my mates appear not to have got the full details - and he deals with legal matters (frightening isn't it)
N Atkins

Sorry - you're right David, apologies for any confusion caused.

LOL Nigel - think it's like the cobblers children ... ;)
rachmacb

Rach... interesting.

AIUI an approved speedo must never under-read - hence most are set to around 5% fast. So I can't see a GPS 'speedo' ever being legal unless made more intelligent (maybe by using an accelerometer)...

A
Anthony Cutler

But is there any definition of what a speedometer is? Does it matter if it is a device that is powered by cable or wireless from e car, or by calculation of the car's position in time and space and comparing it with the next one? Which is after all how Gatsos, VASCARS and even good old fashioned radar works.

Max max-at-midgetmax-dot-com

:)

I'd hate to be thought of as posh, the speaker cable I use isnt co-ax, the original Sigma cable was the co-ax I meant

As for losing magnets, been there, went back for the missing magnuss

I managed to get a replacement from a local cycle shop, cost nearly as much for that as the orignal computer. Some bike shops are very good at "distress purchasing"

(No not Halfords either, Halfords always look after me well with my trade card :) )

Anyway, when I took off the wheel to fit the new magnet (Araldite works well if it can be left long enough to cure off nicely) I found the "lost" magnuss stuck on the wheel rim, it had flown off centrifingally and landed on the steel of my Rostyle's rim.

Still needed another later, lost magnets seems to be the price to pay for accuracy.

Steve, get a wired one so there is no chance of inaccuracy
Bill 1

I have been using a SigmaSport BC1200 for years on my Midget (to say nothing of the BC1606L and BC1609L units on my bicycles). I would not expect the wireless senders to do a very good job of talking through multiple layers of grounded metal, so I haven't bothered to try. Why have more batteries to die on you?

Dunno why one would go to a cycle shop for a replacement battery, as any local hardware store here has them by the job lot.

My units not only go over the ton, they read to 199 (run out of digits there and I have never bothered to see what happens next). OTOH, I have found that the BC1200 has issues with pulses per second (might be fixed in the later units, SS could not tell me). The speed readout is fine, but the "calculated" functions, including odo, come up short. Using a magnet JBWelded onto my brake drum, I have no trouble at any legal speed here in the USA (for that matter, it seems to work fine up to 85MPH). However, when I tried to outsmart myself and use a pickup that watched the driveshaft, I found that any speed over 50 or so would "lose" a lot of miles on the odometers. A trip that I know was in the neighborhood of 750 miles only registered as 400, although speed readouts were apparently fine. I attribute it to the CPU not being able to keep up.
David "my mileage DID vary" Lieb
David Lieb

This thread was discussed between 14/07/2011 and 16/07/2011

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