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New Test Rig. Testing Past 10ms

2958 Views 53 Replies 8 Participants Last post by  Ade, 
Ade
Test Rig currently being built to test up to 15m/s across all id, no it won't be a rug racing affair but purpose built
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As we know Scorpius already tested at 10m/s and passed with flying colours
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i am curious about the reference to 'burying' components at the bottom of slots... which I guess is a reference to SSD IR phototransistors being placed at the bottom of track slots... isn't that an advantage? for example increased vertical separation between LED and phototransistor leads to increased linear interaction length and hence faster vehicle operating speeds... also, it opens up opportunities for surechange guides improving ID readability during tail drift... all good right?

as I say just curious...

c
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For LED-to-Sensor distance the above recommendation for Scorpius appears to be 3mm... but I thought read earlier in the Scorpius installation manual that 4-5mm is recommended for fast tracks... so what is the advantage of going closer i.e. following the above recommendation of 3mm? I guess that is part of the objective of the new test rig... to explore how LED-to-sensor height affects max speed?

Just curious and really it was only Ades earlier comment about burying sensors (presumably SSD related) that got me wondering...

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Yepp - so the new test rig should help? I am thinking a simple graph for the Scorpius system of max speed for 100% reliable lap counting versus vertical separation between LED and sensor.

In general I think SSD keeps the vertical separation pretty much constant (perhaps slight variation of underpan-to-track clearance)... so one less variable to get right... I can see this is either an advantage or disadvantage depending on which lens you look through... mass market versus slotcar experimenter.

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Remember...

kinetic energy =0.5 x mass x velocity**2

potential energy = mass x gavitational accel x height

so the car will be faster at the bottom of the loop... significantly so for the parameters of your system ... with the track sensor or LED (whichever) at the bottom of the loop it would make sense to measure instantaneous speed rather than loop average.

Serious hardware :thumbsup:

c
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If you tilt it reasonable quickly... maybe the non-existence of centrifugal forces (room as frame of reference) will be observed... and the car will be seen launched in a random direction with linear velocity. Excitement for sure :)

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my estimate based on school kid physics... (hopefully)...

change in kinetic energy = change in potential energy

{1/2 m v(bottom)^2 } - {1/2 m v(top)^2 = m g h

where:

m= mass
g = accel of gravity
v( bottom) = velocity at bottom of loop
v(top) = velocity at too of loop

then if we substitute

v(bottom) = v+u
v(top) = v-u

we get:

{1/2 m (v+u)^2 } - {1/2 m (v-u)^2 } = m g h

simplifies to...

2 v u = g h

or

u = gh/2v

then we put in the numbers...

u = 9.81 x 1.81 / (2 x 12.5) = ... ? ... m/s

i didnt even use the sfi equation editor function :)
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Yes... fast is certainly fast... but I am also interested to learn what speed an NSR-F1 with Evo King 50 motor on a 12m drag strip can reach... it will be interesting to compare with Ricks amazing loop... lets see...

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In that case I need to draw on the first law of online physics... never disagree with a moderator :)

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At the bottom of the loop and the speed will be slightly faster than the average so use a trackside speedometer if you want accuracy.

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i calculate the value of u as 0.7m/s

so at the top it would be 11.8m/s and at the bottom it would be 13.2m/s. So doing the trials at the very bottom will get you the highest speed but check precisely with a speedometer. I consider +/- 0.7m/s quite significant if accurate measurements are to be attempted.

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Yepp, and we are also assuming that effects of electrical energy input can be ignored because the cars are close to their max speed - so most of that energy will be converted directly into heat (in one form or another e.g. Ohmic or friction generated).

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Wow... with those temperatures I would want to use electricity to heat my gloves rather than heat a fast moving little slot car motor :)

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Ade said:
Test Rig currently being built to test up to 15m/s across all id, no it won't be a rug racing affair but purpose built :) .
As we know Scorpius already tested at 10m/s and passed with flying colours :thumbsup:
Click to expand...
I thought this thread was about sharing ideas and progress to establish a method for testing slot cars at speeds in the range 10-15m/s. Assuming the plan is to reach the upper end of that range i.e.15m/s then some collective ideas and knowledge sharing may help? right?

We all like slot car bones to chew over... especially those that are race speed related...

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I dont disagree, however in my mind a good raceway (space permitting) should have as big a range of speeds as possible... at one extreme some very tight winding hairpins and at the other extreme some seriously long straights. If I can get cars up to a speed of 9.5m/s and back down to zero in less than 6 metres of linear track powered by an ARC PRO situated on my livingroom rug (which I can) surely serious raceways can achieve that speed or greater on their longest straights? 10m/s seems quite a reasonable and perhaps minimum expectation for accurate speed measurement, car identification and lap recording.

So I think you are right to focus into the10-15m/s zone... and that is why I am a big fan of your new loop endeavour. I just hope you can achieve the 15m/s upper end with all the technology you have in play.

c
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Rick...

when I said <and back down to zero> I meant back to 0m/s i.e. stationery i.e. hard braking to reach a stop. All in slightly less than 6 metres! But next I will be trying 12 metres so max speed will be higher than 9.5m/s for sure.

By comparison an out of the box Scalextric McLaren MP4 with digital decoder can reach 7m/s and then stop in the same distance. And this is with its standard FF slimline motor and standard running gear... no trueing... nothing. Surely our carefully optimised cars can get 50% faster over the same distance?

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A few quick thoughts from me in response, and then I will leave it there...

1/ I use the out-of-the-box Hornby McLaren F1 to represent just that... an out of the box but fast product.
2/ I use the NSR F1 as a representation of a tuned up enthusiast car - switching blades, motors, gears, braids and axle stoppers to get maximum drag strip speed.
3/ the drag strip is not just plastic track - there is a lot of high tech instrumentation... no point in trying to reach into the 10-15m/s zone if you dont know precise speed.
4/ I havent as yet shared any speed data for a 12m drag strip - til now my strip has been just under 6m - I think 5.7m if I remember correctly (can check back).

c

edit: put blades twice... second time I meant braids... now edited :)
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Rick, if you are planning something similar, the dragstrip I used to reach 9.5m/s with a tuned up NSR -F1 was:

4.4 metre acceleration lane with average speed measured over last 0.3metre
short section with ID sensor module
short rails isolator section
auto deceleration zone (Riko method using second powerbase) - need to check length.

Cushion is only required for cases of brake failure.

Its great to see cars wound up from zero to 9.5 m/s then back down to zero again using only motor and then dynamic braking.

I am not suggesting this is better or worse than the 1.81metre diameter loop approach - certainly both approaches are complimentary.

Next time round I am thinking an 8.5 metre acceleration lane as the NSRs have not maxxed out after 4.4metres.

c
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