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#1 Mark Onofri

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Posted 10 February 2023 - 09:26 PM

Is there any reason why, after the finish line,a separate section of braid couldn't be wired to a variable break? It could use a separate power supply and,be wired to a single or, separate break control?
By separating the braid, like a lap counter only longer,it seems very feasible.




#2 Bags

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Posted 10 February 2023 - 10:03 PM

Might hurt the motors running into something like that.

 

Sometimes the braid in the shutdown is put together to make the motors go into dynamic brake mode.


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#3 chasbeeman

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Posted 10 February 2023 - 10:12 PM

I believe Mike Swiss experimented with dynamic break and said it didn't really make much of a difference.
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#4 Paul Menkens

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Posted 11 February 2023 - 01:23 AM

Are we talking about a drag strip here?



#5 Bags

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Posted 11 February 2023 - 07:39 AM

Are we talking about a drag strip here?

Yes


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#6 Paul Menkens

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Posted 11 February 2023 - 07:45 AM

I saw a video the other day where they had a huge amount of goop at the end of the strip to bog the cars down



#7 jamfanwp

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Posted 11 February 2023 - 07:52 AM

The fastest slowdown you will get is for the motor to just loose power. Dynamic braking would only take longer to come to a stop. The only possible way, short of cutting power to the motor, to bring a car to a stop faster would be to reverse the leads so that the motor spins backwards. This is not a good thing for slot car motors or gears. You would throw tire compound all over your car as it spun and hopped after crossing the finish line. It would likely rip teeth off gears on occasion, and possibly take LONGER to slow down at the end of track....

 

The setup at my local track is large amounts of tire glue, to the point it forms a layer over the track surface. From an engineering standpoint, I cannot imagine a more perfect way to slow cars down.... that said, we still do have cars hammer the pillows at the end of the track. Fundamentally stopping the car in a matter of 1-2 feet is GOING to cause damage. It's like trying to slow a bullet down without damaging it, you can only absorb so much energy from the car without damaging it... no matter what  you do.


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#8 MSwiss

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Posted 11 February 2023 - 10:29 AM

All the drag tracks I know of has the power cut at the end. Mine cuts of a few inches after the finish line sensor.

I originally experimented with and without having the left and right braid connected/shorted out in the shutdown.

With some of vintage cars I originally ran, with weak magnets, it didn't make much of a difference.

With current drag cars, using modern motors, shorting the braid, definitely will stop a car a little sooner(a few feet?).

I played around a bit with reverse current from a power supply, not because I was looking to slow the cars down faster, but because I was experimenting with a light system at the finish line that was activated by a car in the shutdown, because we were having guys leaving their cars in the shutdown after passes, when they would be writing down their times,otherwise getting distracted, etc., etc., and then the next racer was running into them.

My choices were to either run 3.5V - 4V reverse, or flip the polarity and run 3-5V - 4V anti-brake.

Using the reverse power didn't dramatically slow the car down or upset it in the shutdown.

But depending on the motor, if left in the shutdown, it would creep backwards.

And the same culprit who would leave his car in the shutdown, that I mostly created the system for, left it in creeping in the shutdown glue for about a minute, and it smoked the motor.

I replaced the motor, a PS S16D, and didn't use the light system the next big race.

He promptly left his car in the shutdown, in morning practice, and 2 nice hardody cars got badly damaged.

I since figured out I could reduce the amperage on the power supply to where it would just power the warning light.

With the low amperage, the motor would not creep backwards but of course, it would also reduce it's braking.

Luckily, AFAIK, I have the longest shutdown in the country, approximately 44 ft.

But even with that long of a shutdown, heavy cars with fast motors get to the end regularly.

With the long shutdown, guys have gotten lazy regluing it.

But when you clean off the old glue, which gets filled with tire rubber, and reglue, if you get too carried away, it's just tears the teeth off the crowns, especially the 64P aluminum ones, or launches the car out of the slot, especially bar cars that don't have a lot of nose weight.

Best advice for running on a short shutdown, use a slow motor.
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#9 Mark Onofri

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Posted 11 February 2023 - 10:39 AM

Ok, it's just that the local track can't utilize the full 1/4 mile. I was hoping to find a way for them to use it. Cutting a hole through the wall isn't a option. I wonder if they might go for a door? LoL

#10 Bill from NH

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Posted 11 February 2023 - 10:54 AM

Does Dan have a drag strip? Or are you drag racing at another shop? Not all 1:1 drag strips are 1/4 mi.. Some are 1/8 mi. or 1000'.


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#11 MSwiss

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Posted 11 February 2023 - 11:20 AM

That's always a dilemma for guys with limited space.

Run a long race with a marginal shutdown length, or a shorter race with adequate shutdown.

I get the impression, after enough cars get wrecked, most go to the shorter run.
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#12 Brian Czeiner

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Posted 11 February 2023 - 12:56 PM

In addition to dynamic braking, we ran light glue the first 12-16 inches then heavy glue after that. Instead of covering the whole track, I used a modified womp chassis with a guide flag front and rear to spread glue in the tire patch area. It had 800 wide tires front and rear. The front had no spacers making the glue patch 1 1/2" - 3 1/4" wide.  We had less mess and used less glue.

We also routed the shut down braid a little deeper than the track surface. This drops the rear tires fully into the brake glue if the car has wheelie wheels. On an outlaw 1000' track, most cars shut down in 6 or less feet. Even our faster 75 MPH cars still stopped in 8-10 feet.


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#13 MSwiss

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Posted 11 February 2023 - 01:11 PM

Cars that run 75mph on 1,000 ft. stop quickly because they are light.

Mike Swiss
 
Inventor of the Low CG guide flag 4/20/18
IRRA® Components Committee Chairman
Five-time USRA National Champion (two G7, one G27, two G7 Senior)
Two-time G7 World Champion (1988, 1990), eight G7 main appearances
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Note: Send all USPS packages and mail to: 692 Citadel Drive, Westmont, Illinois 60559


#14 Tom Thumb Hobbies

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Posted 11 February 2023 - 05:42 PM

Before I sold my raceway I was in the final stages of planning for an 1/8 mile strip. In fact if not for Covid it would have been up and running by June 2020. I was planning on using dynamic braking as an assist for stopping the cars. Since the amount of brake effect you get from dynamic breaking is determined by the motors wind / magnets etc I designed and was testing an adjustable system using a 50 watt potentiometer that the drivers could tune to their liking. Don’t remember the exact value right now. Without a drag track handy I did the best I could simulating one and I think it was worth refining the idea had I continued.


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#15 Mark Onofri

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Posted 11 February 2023 - 07:58 PM

Billnh,yes, Speedies has a 1/4 mile. And,yes, they run a 1/8. I was sceptical at first but, I like the idea of not having rules or, having to turn. A friend who lives a block away texted me, the parking lot is full and so are the side street. It's been a savior for the rest of us!!!

#16 Brian Czeiner

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Posted 11 February 2023 - 11:10 PM

I expect weight was part of it. Proper prep of the shut down area is always a plus.


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#17 Brian Czeiner

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Posted 11 February 2023 - 11:11 PM

Cars that run 75mph on 1,000 ft. stop quickly because they are light.

I expect wieht was part of it. Proper shut down prep didn't hurt either.


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#18 John Luongo

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Posted 12 February 2023 - 05:18 AM

many years ago an intrepid drag racer attached a small estes rocket motor to his funny car chassis. incredibly fast and smokey. caught the foam pillows on fire at the shut down area, went through those. then penitrated the wallboard and started a small fire in that too. wasnt a track record because he didnt back up his time. not recommended.


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#19 Tim Wood

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Posted 12 February 2023 - 10:56 AM

many years ago an intrepid drag racer attached a small estes rocket motor to his funny car chassis. incredibly fast and smokey. caught the foam pillows on fire at the shut down area, went through those. then penitrated the wallboard and started a small fire in that too. wasnt a track record because he didnt back up his time. not recommended.

:dash2:  :sarcastic_hand:  :laugh2: Sorry I am still Laughing.


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#20 Mark Onofri

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Posted 13 February 2023 - 08:09 PM

Wow! I hope your laughing as hard as we did when we read the warning:
"DO NOT LAUNCH HORIZONTALLY"
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#21 Bags

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Posted 14 February 2023 - 07:35 AM

I was in the raceway years ago when a guy did the same thing with a rocket powered car.

 

The track owner installed a fan in the wall to the outside of the building…I know why he did that now!

The whole room filled with that nasty rocket smoke! Took a little while to clear out.


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#22 Mark Onofri

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Posted 14 February 2023 - 04:49 PM

Lost sight of it when it cleared the gole post,ahhha, my misspent youth .
So, I'm guessing that a breaked shut down is a no-go?

#23 Crazy8s

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Posted 03 July 2023 - 06:45 AM

i hav an 1/8 mile track with only 9 feet of shutdown and cars have been .400 @ 62 down it AND stopped in about 3 feet now if the car weighs 200 grams and runs mid 6s that will take you to the very end cutting it close i also have mine goin up hill in the shutdown about 1 inch...nothing crazy just a small lift to slow them a little more and it works well just a thought


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#24 slotcar64

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Posted 08 December 2023 - 01:24 AM

My track , Greenbrier Raceway Dragstrip, is a 1/4 mile HO track. I have return lanes so you need to remember to switch off the return lane (which cuts power and automatically engages Dynamic Breaking) for the 10' shutdown area. I should mention, however, I have a back-up system should you forget to turn off the return lane... a REAL SAND TRAP. :D  Here is info on Greenbrier Raceway's Dragstrip - http://slotcar64.fre...w.com/drag.html


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