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  #16  
Old 04-08-2011, 07:25 AM
Al's slotracing Al's slotracing is offline
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Quote:
Originally Posted by RichD View Post
Provided that there are no breaks in the braid it is easy to get uniform power all around the track. Connect all of the positive leads in one spot and connect all of the negative leads half way around the track. When you do that you will always have the same amount of braid and wire between the car and the power supply. Another thing to remember is that the voltage drop through both the wire and the track braid will vary as the load varies. Since the combined resistance of the wire and braid should be very low that is not a very important factor.
Compared to a single connection to each rail at the same point in the track, that wiring trick does reduce the variation of resistance round the track. However there is still a variation of around 25% round the track (exactly how much depends on the resistance of the cable used to hook it up)
It does that at the cost of increasing the average resistance, so power taps are often used as well.

In fact current is flowing both ways round the lap of braid , so it's not simply a case of always having the same amount of braid and wire between the car and the power supply.

With the higher powered cars which would typically be run on raceway type tracks the combined resistance of the wire and braid is quite important. International rules require extra power taps to reduce the impact of this problem.

While the currents on plastic tracks are generally much lower, the resistance is correspondingly higher so power taps are still often needed.
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  #17  
Old 04-08-2011, 12:56 PM
bibbster bibbster is offline
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This may seem kinds caveman, but here is what I did to see if I needed more than one power tap...

Hook up one power feed to the track (which would need to be completely setup), set your controllers to full on (i used masking tape), set a car in each lane with the rear elevated so they don't go anywhere, and go around the track with your multimeter and test voltage. If you are doing digital use as many cars as your setup will allow, making sure they are at full power.

You may find that you don't need as many power taps as you think. If one does the trick add an extra at the farthest point for redundancy and failover.

I'm not a pro racer nor am I an electrician, but this worked for me...YMMV.
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  #18  
Old 04-08-2011, 02:40 PM
Al's slotracing Al's slotracing is offline
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Quote:
Originally Posted by bibbster View Post
This may seem kinds caveman, but here is what I did to see if I needed more than one power tap...

Hook up one power feed to the track (which would need to be completely setup), set your controllers to full on (i used masking tape), set a car in each lane with the rear elevated so they don't go anywhere, and go around the track with your multimeter and test voltage. If you are doing digital use as many cars as your setup will allow, making sure they are at full power.

You may find that you don't need as many power taps as you think. If one does the trick add an extra at the farthest point for redundancy and failover.

I'm not a pro racer nor am I an electrician, but this worked for me...YMMV.
Very sensible way of doing it, in fact that's pretty close to the way the experts do it - except they use a resistor rather than a car.
That's about the best way for finding faults, and of course theoretical calculations only tell you what the resistance should be if it's done perfectly, not where the faults are.

Using a resistor gives more repeatable reading which can be handy for figuring out where the faults are, it also saves wearing a car out and there's no risk of a resistor driving off and crashing if you don't chock it up right.
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  #19  
Old 04-08-2011, 03:49 PM
RichD RichD is offline
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The trick only works if all of your connections are perfect, so it mostly applies to braided tracks. Sectional tracks will often need jumpers. When I am testing a track I use a light bulb as as a load. A 200 watt bulb uses about 400MA at 12 volts.
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  #20  
Old 04-20-2011, 12:37 PM
Mike- Mike- is offline
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Al's -

As far as the power calculation I posted.
Your "not so good for slot car tracks" comment is not entirely correct.
power loss is power loss.
Feet...even inches will cause power loss, whether it's in your house, in your car (full size), high power or low power....extened length wiring causes power loss.

And while that calculation page I posted isn't exact, it IS a very good reference to go by.

I've discussed this with two different track builders (one building a track for me now), both agree, it is a very good starting point. And can very easily be used as a method to wire a track..!

This is from two different people that do this for money...and to keep customers happy..!

Mike
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  #21  
Old 04-20-2011, 10:10 PM
scrjon scrjon is offline
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I have a 4 lane carrera 185 feet long analog I use the pyramid 26k, it has a fuse and on all of my drivers stations I used fuses and a directional switch
I have 30 power taps and that ain't enough, but i painted the track joints with a circuit writer pen it has conductive bits in it and that helped, for wire I used 12 gauge 4 wire flat like in truck trailers it worked great and a dob of hot glue sticks it good hope this helps
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  #22  
Old 04-20-2011, 10:19 PM
speedyspyder speedyspyder is offline
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Quote:
Originally Posted by Ponderwilu View Post
Hi All, I've already read thru the many threads here at SCI covering track wiring and power taps.
http://slotcarillustrated.com/portal...light=zippydog
I'm a "newbie" and would like you guys to "sign-off" on my plans to provide track power to "Project Talladega" (see my thread in the Carrera section).
I have a Pyramid PS26KX 22 amp power supply, 250 feet of 4 conductor 16 guage stranded wire and four heavy duty 8 lug terminal blocks from Slot Car Corner.

http://www.slotcarcorner.com/product...nal-Block.html

Here's the game plan...
1. Cut the wire that connects the Carrera supplied power supply to the BB. Plug the connector end (of the wire I just cut) into the BB as usual but the "cut" end will now go to the Pyramid output instead of the factory wall transformer. I plan on inserting an "in-line" fuse on the positive lead of 7 amps. I remember reading here with six cars you may approach a 6 amp current draw...Yes/No?
2. Go underneath the main piece of power track and connect four wires. Each wire will be run to one side (jumpered together) of an 8 lug terminal block. From those four terminal blocks I will connect eight 4 wire "trunk-cables" that will feed current to different sections of my 186 foot layout.
3. I may (if you think I should) insert another "in-line" fuse on the power side of each lane between the terminal block and the underside of the power track. Lets say 3 amp each lane. Yes/No?
4. Each of the eight "trunk cables" will be run out to different sections of the layout. I will "splice" the end of each "trunk cable" with two more 4 conductor 16 guage wires and use these to "branch-out" 12 feet in either direction thereby giving me a total of 24 power taps.
5. I will strip each end of the 16 guage wire (that is color coded for proper connection points) about 2 inches, fold it over and tuck it into the underside of the Carrera tracks. Then duck tape the area for a secure fit.






If you guys would please let me know what changes or additions I need to make to these wiring plans before I goof up I would really appreciate it. Thanks for any input.
side note...dry wall?
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  #23  
Old 04-21-2011, 12:07 AM
Al's slotracing Al's slotracing is offline
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Quote:
Originally Posted by Mike- View Post
Al's -

As far as the power calculation I posted.
Your "not so good for slot car tracks" comment is not entirely correct.
power loss is power loss.
Feet...even inches will cause power loss, whether it's in your house, in your car (full size), high power or low power....extened length wiring causes power loss.

And while that calculation page I posted isn't exact, it IS a very good reference to go by.

I've discussed this with two different track builders (one building a track for me now), both agree, it is a very good starting point. And can very easily be used as a method to wire a track..!

This is from two different people that do this for money...and to keep customers happy..!

Mike
Mike
OK, lets see what needs correcting
power loss is power loss.
We are both saying power losses exist, the question is how much.

Feet...even inches will cause power loss, whether it's in your house, in your car (full size), high power or low power....extened length wiring causes power loss.
Agreed, as I correctly said in the previous post "you never get 0 voltage drop (except at zero amps" - this was in response to your until you get "0" voltage drop. point.

And while that calculation page I posted isn't exact, it IS a very good reference to go by.
As I said previously, that calculation page is good for a single wiring run from point to point.
To calculate what happens in a slotcar track with power taps is a more complicated, that calculation page can be used to do a very simple step in this calculation.
Simply using that calculation page without a understanding of what is really going on will very substantially over estimate the resistance in a slotcar track with power taps.
This will lead to too much power tap redundancy. That works well (unlike not enough). The downside is that extra wiring costs money. The extra cost may be unimportant for the wiring needed for lower powered cars, but can be a important for tracks intended for higher power cars where more and thicker wiring is need

I've discussed this with two different track builders (one building a track for me now), both agree, it is a very good starting point. And can very easily be used as a method to wire a track..!
The professional track builders I've come across work from experience of what wiring is needed rather than doing calculations. Experience such as learning where extra taps were needed on previous tracks that had a power problem. Once they have the necessary experience, it is an entirely satisfactory way producing a track that works well, they don't need a detailed theoretical understanding of what's going on in the wiring.

This is from two different people that do this for money...and to keep customers happy..!
It's good for business to agree with your customer whenever you can. Unwise to risk making the customer unhappy by pointing out their mistakes if you don't need to in order to get the job done.

Al

Last edited by Al's slotracing; 04-21-2011 at 12:09 AM.
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  #24  
Old 04-22-2011, 05:46 PM
slotcardaniel slotcardaniel is offline
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I was reading this thread and I believe this data will be useful here.

I have a Carrera track with all the new digital toys. I setup a 10 AMP variable supply with a 5 AMP and a 6 AMP fuse in line (positive line) between the CU and the power supply. Carrera digital can not take more than 7 AMP.

The track is wired like an analog track. I had not idea that it was no necessary to do it in that way.

When the CU and all the accessories in the track are on, 1,5 AMP is used. Running 1 car with modified magnets (bigger than the factory magnet) another 0.5 AMP is used (top 2 AMP).

With 5 autonomous cars plus the car I was driving (total 6), all the cars with more powerful magnets than the originals, the Maximal use was 3 AMP (with all that load !!!).

Those are the values I am reading in an MG 10 AMP variable power supply set-up at 18 V .

I believe I am cover with my 5 AMP fuse plus the 6 AMP just in case.

Comments ?

Some pictures of my track.

Daniel
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