Help troubleshoot inconsistent timing system

Late_nite_racer Friday, 1/19/2024

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Hi all, newbie here. 

I've been racing with my kids since around 2017. We started with stunt tracks and then got a super 6 lane raceway. Drag racong is what really got me hooked into the hobby.

I recently completed my first custom drag racing setup. Its been in the works since 2022. The final piece was a digital timing system, the Slanman Customs dts-2. 

I already had a functioning start gate with wireless release so I opted to only use the finish gate. I fabbed a bracket to mount the micro switch from Slanmans start gate to my existing setup. 

I was so excited to finally be able to accurately compare my cars and establish time based rankings. 

Unfortunately,  from day 1 I've gotten a lot of variance in the times. As much as +/- 50 thousandths on back to back runs. I originally thought it must be shortcomings of my start gate or track and set about improving anything I felt was a weak point. After covering all my bases I tried it again last night with the same results. 

I contacted Slanman and he has been responsive, but we havent figured out the issue.  Hopefully someone here can help.

I recorded 3 consecutive runs last night. The first two races I used  the pro circuit funny cars as my test mules. I got 2.111 (King Kenny lane 1) and 2.119 (John Force lane 2). Then  2.140 to 2.145 no lane swap.  The last race I swapped John Force for the Back to the Future 3 time machine. This time King Kenny ran 2.097 in the same lane.

I can't understand how its varying by 43 thousandths on back to back runs, same car, same lane. This is using a spring loaded drop gate with a door lock actuator pulling the release trigger.


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Hey there !

Welcome to RLD! Great to see you are racing with your kids and progressing to more!

Gee, I can imagine the frustration, of doing "all the right" things and having inconsistancies that make you go ?!!

Hard to analyse from a far, other than knowing I spent a lot of time trying to work out all these issues, and keep to a minimum.

If I were having the issues you described, my investigation would go straight to one of two issues; The trigger point and the micro switch, and the relationship between the actual moment of trigger. As you have a consistant start mechanism, this "should" be ok. It does not take much for operation of the "on/off" part of the microswitch to be slightly off, or slightly slow at times. It is probably where I would look first. Usually the easiest test is to substitute. (But after you checked actuating limits etc)

Again, hard to call from a far. I hope this somewhat assists. Wish you the best.


Thanks for the reply CutRockR. The switch and trigger interface is something I had considered.  In fact, the last thing I did was to make a stiffer mounting bracket for the switch as my first one flexed a little when the trigger depressed the switch.  The new bracket is much stiffer. I can still see the slightest of movement while setting the trigger, but once set it doesn't budge. I guess I'll make a brace so its rock solid but it looks inconsequential.  Pics and video to follow.

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dr_dodge 1/20/24

this is a possible source
remember that tiny time error requires only tiny inconsistancy


That switch arm should not be compressed against the switch body. If you press the switch arm down, you should feel the switch trip and it should trip well before the switch arm contacts the switch body. Your sweet spot will be where the lever moves and releases the car and the switch makes/breaks to start the timer. Adjust the switch bracket or linkage to acheive that. The good news is those micro switches actually have good repeatability when properly set up!

I do not know that system in particular, but as the Dr. says... you are dealing with thousandths of a second and every bit of slop or play with the linkage and the switch will be part of your error.

Hopefully others will chime in with their experiences...

Good luck with it!

  • I agree with fred, the micro swith tip should be doing all contact with the arm — dr_dodge
  • I also prefer roller tip micro switches over the flat tab. It is made for the movement across the tip. flat tad arms should only push 90° to the switch — dr_dodge

I've recieved some good advice. Thank you guys again.  I decided to relocate the switch above the drop gate. There's just enough space between the bottom of the base board and the top of the gate. That should eliminate variance due to play/slop in the arm to actuator linkage. The timer will start closer to when the cars are actually leaving. I'll update once that's done.

Got it done and tested. Times are still all over the place. I'm about ready to go back to the Super 6 finish line.

  • thats a bummer, try a different switch? — dr_dodge
  • Yeah i guess they're cheap enough. I'll give that a try — Late_nite_racer
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TuxMcBea 1/21/24

What is the track (and the switch) mounted onto? Is it foam board? Any "give" in that?

  • 5/16" thick pvc trim board. No flex that I've noticed. — Late_nite_racer
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Chaos_Canyon 1/22/24

I would also have said the microswitch would likely be the issue. On my track (being open track) it is hard to get consistent times because even a small deviation on a wide track can have large differences by the bottom but I did have issues with my microswitch being in a similar place to yours. For me it turned out there was a small amount of flex in how it was mounted and that was enough for it to not even trigger sometimes. I changed my mount and got over that issue but they can be finicky. If you are triggering your start gate via switch, can you not just run that as your start timer switch as well. The actual times won't matter if it is from when the car leaves or when the start button is pressed as long as it's consistent. At least that way you'd completely eliminate things like sway/movement etc. It's what I went to on my second timer system and it works even better than my first version.

  • 100% Micro switches can be very finicky. All a challenge to minise the inconsistencies! Cheers — CutRock_R_Marc_D
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DXPRacing 1/22/24

When I first got my setup I experienced the exact same thing.  Times were all over the place and no consistency whatsoever.  Those little micro switches can be very inaccurate at times.  I swapped mine out for a more robust switch and all of my issues went away.  I would suggest you do the same.  Hope that helps.  

  • with electronic switches and sensors, there is no doubt good quality costs $$$, too. save a dime, and lose a dollar kinda thing — dr_dodge
  • DXPRacing I follow your channel and definitely recall you mentioning this. Guess I just need to figure out what switches to order. Pretty sure I found what the current switch on Amazon. 20 for $4 shipped. So yeah cheap cheap. — Late_nite_racer

Figured I should update this. I've been busy revising my start gate and release mechanism.  Here are the things I addressed this time:

- noticed a bit of play in the pvc tees I was using as hinges. Replaced with new tees that had to be filed to fit. No more play.

- release lever mounting bracket was slightly twisting under tension from the dual start gate springs. Made a wider and thicker mounting bracket. Used larger diameter for bolt, washers, and nylon spacer. Extremely tiny shift downward remains when the gate is locked.

- release lever was actually bending under tension from the dual springs.  Upgraded from unknown 1/4" wood to 1/2" oak. Shortened lever to less than half its original length. Fixed.

- questionable micro switch was replaced with a magnetic reed switch. I also tested an Omron micro switch just for good measure. 

The end result? Times can be consistent for a handful of runs, BUT always end up  going wacky.

I hate to say it but at this point I'm pretty well convinced that the timer itself has issues.   I can reliably demonstrate inconsistencies that I find difficult to attribute to anything else.

Run 2 cars for 5 races same lanes....times will usually be consistent. Swap lanes and the times will always increase 20-30/ 1000ths for BOTH cars.   I know lanes are never 100% equal, but?

If the car in lane one has 10 consistent passes (within +/- 5/1000ths) .  All I have to do is change the car in lane 2 and all of a sudden car 1 times change  by 30 to 40/1000ths.  

Usually timing a car you get an idea what it will run on average.  With this timer, it will literally change every time you change the car its racing against.  Not by small amounts either. 

End rant for now.

  • Does anyone know how the slanman timer detects when a car finishes? Is it just a motion sensor? — ConMan_Customs
  • Individual phototransistor and reciever for each lane. — Late_nite_racer

What is used to trigger the stop of the timer? Could it be the placement of where that is or where the cars cross the line, if they are slightly more to one side of the track than the other could that be changing your times? Is it at least picking the correct car/lane for the win. Is that not the most important aspect or are you running a specific leaderboard so it it the cars time that matters most?

  • The finish gate has the common ir transmitter above/ reciever below setup built into the 3d printed finish gate. Can't imagine the 3d print alignment is off. I had a close look it last night just to make sure there wasn't any dust or plastic bits blocking the sensors. It looks great. No problem displaying the correct lane/winner. — Late_nite_racer
  • I'm wanting to set up weight based ranking of my collection. Ultimately the best times in head to head racing is what would determine order. Thought I would be able to choose which cars to race based on what they typically run. — Late_nite_racer

 While resesrching switches, I read about contact bounce with both micro and reed switches. Wondering if that may be a factor here. 

Apparently if the timer isn't programmed to latch after the first change detected from the switch, the time can be reset prior to the cars breaking the beam. 

This timer definitely resets if you close the switch mid race. 

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