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Old 05-30-2007, 08:24 AM   #16
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This weekend I'm trying fiber concrete tubing that I'll cut down so the bridge fit's into it then drop a sandbag into it where the vertical pole of the bridge resides.

http://www.helixgate.net/AO/ao5.jpg
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Old 06-26-2010, 03:19 AM   #17
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Old thread revival...

I'm interested in any pics y'all have or descriptions of timing loop bridges (like the ones in the BPS Series pictures above).

Or if you have a link to a better thread for information on timing bridges. I am considering trying it at our track but would rather avoid others' mistakes.

In particular I would like to keep it from sagging. I'm also considering camouflaging the loop as a track design element such as the Dunlop arch

http://farm2.static.flickr.com/1295/...16acf9.jpg?v=0

that crosses the 24 Hours of LeMans track.

Or like this one

http://www.roadcarvin.com/sites/defa...nish%20Now.JPG

We have 2x4 boards as barriers and I would like to minimize or better yet eliminate the amount of the loop that stands on the track surface as many times the lanes run back to back sharing one board.

Ideas? What do y'all run at your track with a non permanent loop? I am totally open to out of the box solutions!
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Old 06-26-2010, 05:53 AM   #18
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Here's a pic of our old beloved nitro on-road track that's long gone. You can see the basic shape of the timing bridge, It's made entirely of PVC tubing (I'm pretty sure it's 1 1/2" or 2" OD). The curved sections at the top are what keeps the bridge from sagging in that they are under tension slightly pulling the bottom of the bridge upwards. These pipes are connected in the middle with a Tee. The bottom of the bridge is a two beam construction about a foot wide(long rectangle) with a crossover in the middle connected to the tension pipes with a tee. Basically the whole assembly is constructed with PVC pipes, tee's and 90's. The "Bridge" is pretty solid and resisted sagging through many seasons even through the intense Hawaiian summer.
The timing loop/wire is threaded inside the pipes through holes with electricians fish tape.

I'm sure you could install a fiberboard panel in the open sections under the curved pipes to emulate a real bridge by placing sponser and club decals etc. but keeing it open allows drivers to see their cars as they pass under and beyond the bridge
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Last edited by FREAKAH; 06-26-2010 at 03:39 PM.
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Old 06-26-2010, 10:14 PM   #19
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Quote:
Originally Posted by FREAKAH View Post
Here's a pic of our old beloved nitro on-road track that's long gone. You can see the basic shape of the timing bridge, It's made entirely of PVC tubing (I'm pretty sure it's 1 1/2" or 2" OD). The curved sections at the top are what keeps the bridge from sagging in that they are under tension slightly pulling the bottom of the bridge upwards. These pipes are connected in the middle with a Tee. The bottom of the bridge is a two beam construction about a foot wide(long rectangle) with a crossover in the middle connected to the tension pipes with a tee. Basically the whole assembly is constructed with PVC pipes, tee's and 90's. The "Bridge" is pretty solid and resisted sagging through many seasons even through the intense Hawaiian summer.
The timing loop/wire is threaded inside the pipes through holes with electricians fish tape.

I'm sure you could install a fiberboard panel in the open sections under the curved pipes to emulate a real bridge by placing sponser and club decals etc. but keeing it open allows drivers to see their cars as they pass under and beyond the bridge

Very nice. Thank you. I may have to PM you when I get this started...
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Old 07-06-2010, 11:59 PM   #20
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Quote:
Originally Posted by andrewdoherty View Post
Very nice. Thank you. I may have to PM you when I get this started...
http://www.rctech.net/forum/7638010-post4.html

OK, thanks to Freakah the bridge is complete and looking great.

I have a new issue now...

Our current loop is laid about a half inch below the carpet we race on. It is buried in a concrete slot and is connected to an AMBrc decoder (no lcd and no adjustment for squelch/sensitivity that I can find). The decoder is about 100' away. Currently our cars read fine as all of the PT's pass within 3 inches above the loop. If the PT is raised past 4 inches though the current loop doesn't detect the PT or house transponders. I tried a bunch of different configurations changing all kinds of parameters with the loop in the new bridge but none of them allow a car to pass under the bridge and trip the loop. I have added another 100' of coax to get the new timing bridge in position but none of it is kinked.

I varied the width of the loop from 2" to 14"
I made sure none of the loop was coiled or doubled back on itself
I tried a resistor our track owners say works
I have NOT yet tried the original AMB resistor
I tried no resistor
I tried using the yellow AMB loop wire
I tried using just the white section of servo wire
I tried connecting all three servo wires

We are running RCSP and if I lay the loop on the ground and run a car over it with a PT in it, the loop trips and I get good signal strength (both the H and S are something like 120 and 180). But if the loop is any farther than 4" from the ground, the PT won't read. I ran out of time tonight, but next time I go out I'd like to get our timing bridge working. Any suggestions? I see so many outdoor tracks with timing bridges I know someone out there has experience with this . . .

How can I increase the loops sensitivity?

If it matters I just realized we are using this connection box

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Last edited by andrewdoherty; 07-07-2010 at 12:53 AM.
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Old 07-07-2010, 12:22 AM   #21
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http://www.mylaps.com/kb/en/b2b/Manu...r%20Manual.pdf

http://www.mylaps.com/kb/en/b2b/Inst...-rc_MYLAPS.pdf

For those interested...
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Last edited by andrewdoherty; 07-07-2010 at 12:52 AM.
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Old 07-07-2010, 01:19 AM   #22
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I found this as well but lots of the info went way over my head.

http://www.rctech.net/forum/electric...need-help.html
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Old 07-08-2010, 12:10 AM   #23
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Alright: Update.

I made it back to the track today and tried the following. I disconnected our off-road loop and attached the connection box to the off-road run of RG-59 coax. I then connected the amb yellow loop wires sans resistor and layed it over the bridge. This actually worked correctly and allowed the bridge to pick up a transponder slid though on the ground 14+ inches away. So it looks as though the problem is the fact that I used the wrong coax to extend the on-road loop 100'. All of this is getting confusing. The amb manual specifies 75 ohm dual shielded coax, which from all I can read on the internet can be dual sheilded RG-59 or dual sheilded RG-6. The manual also specifies that not more than 330' of coax be used between the decoder and connection box, which I am well within even with the 100' RG-6 extension I tried.

Could someone look at their loop and tell me what type of coax is running between their decoder and connection box and how many feet apart the decoder is from the connection box? Even if you could just list the numbers/letters etc on the jacket. I am curious to know if both RG-6 and RG-59 are compatible as long as they are not used in combination perhaps?
The presence and number/type of connectors involved would be nice if you notice as well...
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Last edited by andrewdoherty; 07-08-2010 at 01:36 AM.
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Old 07-08-2010, 12:08 PM   #24
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Quote:
Originally Posted by bvoltz View Post
Over here in Jackson we use PVC, 2" inside, 4" outside. But we have heated and bend the pipe for corners.... We run 1 a month at the local Bass Pro.... Next race is June 9... Come over for some run and racing...
Sure hate i missed that. im from jackson.
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Old 07-08-2010, 12:49 PM   #25
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Check list... hope you have a simple/cheap meter.

1) Most tracks don't have this option, but all my loops are detached from the COAX... so when I set-up I check the value of the resistor... should be 470ohms. .99 at Radio Shack for a pack of 5.

2) Check the background noise. Never been able to get my hands on RCSP, but it must show it somewhere. In the software I use, its in the transponder test window. Its usually between 20-25... 50 and higher and you will have problems... 80-100 forget it. I check this right after everything is set up.. better then starting a race and having half the cars not counting.

This problem is "usually" tied to the COAX or that box (matching transformer). Test the box with a meter... should read 100k ohms across the thumb screws, and also across the center pin to the outer shell of the BNC connector... the same thing goes for the yellow AMB cable with the box molded on.

I have one of those old TV matching transformers... has a value of something like 5 ohms. Will it work??? haven't had time to play with it.

Also could be bad/dirty BNC connectors.

The AMB COAX is "I think" around 70'.... but I have longer and shorter ones. Nothing on it... they whiped it clean. You will find COAX in both 50 and 75 ohm... does it make a difference??? I've always used 75... cause the spec it.
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Old 07-08-2010, 01:52 PM   #26
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Thanks for the details about how/where to test the components. I'm headed tro Memphis this weekend, but when I get back I will be knee deep in getting this to work. I'm wondering how significant the difference between 75 ohm RG-6 and 75 ohm RG-59 is when it comes to scoring systems . . .
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Old 07-12-2010, 10:03 PM   #27
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It turned out that the problem was the quantity/quality of connections we had in line between the decoder and the loop. I ran a fresh 250' line of RG-6 straight from the decoder to the loop and it works awesome now. In fact I can raise the loop another foot or two and still get good reception. Bottom line is use RG-6 or RG-59 and use up to 100 meters (~330 ') with no connectors. Perfect reception!!
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