Transponder question

[SZRacer]

Just a quick one - can a transponder be mounted inside a car, or does it have to be outside/underneath the bodywork?

Regards,

James W

[Tim Falce]

It depends what the car is made of. I have mine mounted in the passenger side of the car but the body is fibre glass. I am not sure if the signal would be read through metal.
We have a Fiesta with the transponder mounted at an angle (45deg) on the engine bulkhead and that also seems to work OK even though it doesn't have the recommended straight line to the road.

[Barry Pomfret]

Our Formula Ford transponders are mounted on a top chassis rail above the drivers legs, have worked fine like this and never any complaints from the timekeepers.

[R59]

I was going to mount mine on a 20ft pole out the front of the car.

On a serious note, it should be mounted with clear view of the track beneath it, ie: no metal below it.

You should also mount it as far forwards as you can (hence the pole joke)

Rob.

[dtype38]

Funny you should mention mounting it as far forward as poss Rob. I know some of the cars I race against have them mounted just behind the driver, but mine is in the nose of my bonnet. So..... If I crossed the line a bonnet length behind another car, but my transponder was in front of his, would the MST system of using a light beam and the transponder for ID only allocate his time to my car?

[graham bahr]

several saloon car racers i know including my self strap the transponder to the main uprights of the roll cage so you can see it through the rear quarter windows, it seems to work just as well irrispective of if your windows are plastic or glass.

i talked to MST about this and they said it works because the transponder sends out its signal in a big arc not just out its base.

not sure how the location will effect the position allocation though, i once had a dead heat at snet, the system gave us a dead heat with identical times, but the win went to the other guy because from about he looked to be in the lead!

[Al Weyman]

Naw its no good just having it on a long pole out front Rob, it needs to be on a moving track so it can slide from one end of the car to the other as you cross the line:-)

[greenamex2]

As far forward as possible. It might just make the difference in a 'dead heat'.

[GordonG]

AIUI the transponders are not used to determine times, only to identify cars. Silly, eh? The MSA demands human timers, so it doesnt matter where in the car (from a performance perspective) you mount the transponder. This amazes me as we have to fork out for hte technology but it's not being used to its full effect. There have been plenty of words written on this in other threads so let's not restart that one. We were specifically told that it doesnt matter where on the car its mounted from a timing PoV.

The destructions on my transponder recommended that it have a clear view of the track unimpeded by metal or CFRP. Glass, wood etc is fine.

G

[Chris Y]

Originally Posted by graham bahr

several saloon car racers i know including my self strap the transponder to the main uprights of the roll cage so you can see it through the rear quarter windows, it seems to work just as well irrispective of if your windows are plastic or glass.

Same here. Our championship actually did some signal tests (along with some Caterhams I believe) with MST, and found that the best signal actually came from having the transponder on the main hoop just behind the driver!

Currently transponders aren't used for timing, and never used to determine finishing positions, so you don't need to worry about having them stuck on your front bumper just yet.

[Tim Falce]

One other point on location, if it doesn't transmit the signal properly first time out, you will still get timed but asked to get it working.
I re-wired one on Sunday for a chap who's transponder didn't work. He had wired it into the side-lights connector on the fuse box and also didn't realise the transponder has a tally light to show when it is or isn't working.

[zefarelly]

mines wired to the soleniod so it goes on when the cars on, its bolted to the inner wing behind the front wheel, never had any problems, and to be honest forget its there !

[SZRacer]

Thanks, all for the comprehensive replies.

I now am deciding whether to go for the roll hoop mount, or front of engine bay. I may try both!

Luckily, since I went for the rechargeable model, at least I don't have to worry about wiring so much....

Cheers,

James

[Larry J-Croft]

Originally Posted by GordonG

AIUI the transponders are not used to determine times, only to identify cars. Silly, eh?

This has been discussed elsewhere on the forum, but as I advised the MSA on the feasibility on using them for timing a couple of years ago (I worked for a company that made similar technology) I will just explain what the problem is.

The transponders work on a very low magentic frequency (125 Khz for all you anoraks) and so the field generated by the receive aerial in the track is about 1.2 metres wide. Unfortunately it is affected by water, atmospherics and time of the day. Also how far the transponder is in to the field before its code is read can vary depending on the location, distance, mounting etc. Take these variables in to account and the MSA requirement to measure time to one thousand of a second and, if I remember correctly, you have to be going at least 700 mph to reduce the variations to acceptable limits !!!

To accurately time cars you would need to use a microwave system - and it would not be cheap, especially after we have all had to fork out for these perishing things. Of course you might ask why the MSA need such accurate timing, but then you will start me off talking about why we need to replace seat belts after a few years when the aircraft industry don't and why we need all these different competition licences and why the inside of my crash helmet now needs ot be flameproof etc etc etc.

[dtype38]

Originally Posted by Larry J-Croft

This has been discussed elsewhere on the forum.... and the MSA requirement to measure time to one thousand of a second and, if I remember correctly, you have to be going at least 700 mph to reduce the variations to acceptable limits !!!

and clubbie racers need 1/1000th accuracy? What would be the speed if we only wanted 1/10th?

[Larry J-Croft]

Good question D type, in theory only 7mph. That would give you acceptable lap time but you will still have the problem of judging dead heats, unless the transponders are all mounted in exactly the same place, there are no puddles on the track, the transponder batteries are all performing the same etc etc.

More to the point when did the MSA ever relax rules to make things better/easier for club races ???

[Chris Y]

Why don't we all have a little alloy sheet affixed to the bottom of our cars with a barcode printed on it, and then when we cross the line, there's a gurt big scanner under the track like at Tesco

[MGDavid]

...I supose I'm flogging a dead horse, but how do the karting fraternity manage to do all their positions and timing with just transponders then?

[Larry J-Croft]

Much closer to the ground, in a similar position on vehicles that are all the same shape and I expect they may not time to 1000th. Also are they similar frequency? The ones we use could not be on a worse one for accuracy!!!