[WIP] 40+ km/h racer - need your help!

[TechnicRCRacer]

Just now, PorkyMonster said:

Did you test out that model with springs (gotta be hard springs though...)? Weight gain should be quite negligible... no?

I do suspect that at that speed (which is "dangerously fast" relative to its size), tiny bumps (which can be many for a car that small... even on surfaces we think are flat) will send the wheels spinning the in air and lose traction momentarily regardless of weight distribution - and suspension might help to regain all that lost traction and get you to 40 km/h 

Would it overcomplicate the model?

[Aventador2004]

1 hour ago, TechnicRCRacer said:

Would it overcomplicate the model?

I doubt it, the attachments on the rc unit should help.

[mocbuild101]

Just now, Marxpek said:

I have tried this with a camera at 60 fps on a section of 10m, it gave very inconsistent results, so i ditched this way of measuring speed, it will also never show you the top speed.

Measuring it over 10m is why it was inconsistent - unless it was perfectly flat, the car would speed-up and slow-down many times over that distance.

Just now, Marxpek said:

Have you already done a test run with your car? You will notice that every run is different from the next and the exact section you need to film is on a other spot on the track on every attempt. Filming for speed sounds easier then it is.

No, but I have tried it with my RC car (which the results came very close to what it was suppose to be) - which I did by putting two lengths of white tape 2m apart, and filming multiple times to get the fastest speed over that spot.

Just now, Marxpek said:

(besides the fact people will distrust it since you can easily edit it faster..)

There are also ways to cheat with GPS or the speed computer (driving around in a real-size car with the GPS, or attaching a motor directly to the speed computer).

[TechnicSummse]

2 hours ago, mocbuild101 said:

There are also ways to cheat with GPS or the speed computer (driving around in a real-size car with the GPS, or attaching a motor directly to the speed computer).

Thats the point... at the end evry thing shown in a video could be cheatet :(

4 hours ago, PorkyMonster said:

Did you test out that model with springs (gotta be hard springs though...)? Weight gain should be quite negligible... no?

I do suspect that at that speed (which is "dangerously fast" relative to its size), tiny bumps (which can be many for a car that small... even on surfaces we think are flat) will send the wheels spinning the in air and lose traction momentarily regardless of weight distribution - and suspension might help to regain all that lost traction and get you to 40 km/h .

Sadly i dont have hard sprigs, but i dont think it would help... because:

I did so many different comparing-runs at different speeds with GPS and Speed computer... wich gave me all pretty much the same results.

If there would be a wheel-spinning-problem at higher speeds, the gap between speed-computer and GPS would be growing with speed... the speed computer would show much higher results, the higher the speed is... but IN FACT it is not like that ;)

So i guess there is close to no spinning.

[rm8]

 crazy record breakers

What is your maximum running speed?

[PorkyMonster]

1 hour ago, TechnicSummse said:

I did so many different comparing-runs at different speeds with GPS and Speed computer... wich gave me all pretty much the same results.

If there would be a wheel-spinning-problem at higher speeds, the gap between speed-computer and GPS would be growing with speed... the speed computer would show much higher results, the higher the speed is... but IN FACT it is not like that ;)

So i guess there is close to no spinning.

Agree with your reasoning that there is probably no need for suspension in this case.

For the sake of discussion, I suspect that there is close to no spinning (effect wise) probably because (1) there is zero bumps? (quite unlikely), or (2) those bumps you hit were not large enough to impact your car's momentum significantly, such that even if lifted off the ground, the "flight" time is very short, and perhaps coupled with that, (3) your wheels are probably turning at its max capacity already while on the road, so it has no "motivation" to spin any faster when traction is lost momentarily. 

Edited June 26, 2017 by PorkyMonster

[Marxpek]

what are those rubber bands doing in your steering setup? That is no Lego ;) 

And i do agree on the suspension part, i started out with (hard) suspension, but it gave a lot of problems with the rigidity of the frame and thus the steering, not to mention the weight gain and the fact we MUST do this on a fairly clean track or the run is lost anyway, we should not need suspension, just try another run when we crash ;D

[TechnicSummse]

4 hours ago, rm8 said:

 crazy record breakers

What is your maximum running speed?

GPS says its ~27 km/h max 

 

4 hours ago, PorkyMonster said:

Agree with your reasoning that there is probably no need for suspension in this case.

For the sake of discussion, I suspect that there is close to no spinning (effect wise) probably because (1) there is zero bumps? (quite unlikely), or (2) those bumps you hit were not large enough to impact your car's momentum significantly, such that even if lifted off the ground, the "flight" time is very short, and perhaps coupled with that, (3) your wheels are probably turning at its max capacity already while on the road, so it has no "motivation" to spin any faster when traction is lost momentarily. 

Yes... and... you should not forget wheels themselve are absorbing a lot

 

3 hours ago, Marxpek said:

what are those rubber bands doing in your steering setup? That is no Lego ;) 

And i do agree on the suspension part, i started out with (hard) suspension, but it gave a lot of problems with the rigidity of the frame and thus the steering, not to mention the weight gain and the fact we MUST do this on a fairly clean track or the run is lost anyway, we should not need suspension, just try another run when we crash ;D

Rubberbands are the GPS-Phone-holders :D

You can see this in the record-racer viedo at the end... look at the gps/speedcomputer comparing-pictures there ;)

[TechnicSummse]

Todays results:

-> nothing good :(

I just tested yesterdays building resulst, without any changes, because i decidet to not like this design so i will disassemble it again. And i didnt want to loose a chance, if this maybe could give a good result, so i testdrove it.

-> 4 Motors gave only 35,5km/h :(

A few problems leading to this could be:

- Axle bends to much, and so wheels fidget

- too low ground clearance breaking at small stones

- look the last picture :D

 

The only good thing i found with this test -> with the 24:12 gearing the battery-box-protection doesnt kick in.

Edited June 26, 2017 by TechnicSummse

[mocbuild101]

I think I have thought of the most accurate speed measuring possible: Mindstorms! (EV3)

I'm going to do some tests today, but I think this will be very accurate: 2 light sensors (some distance apart, with a bright torch pointing at them) will detect the passing of the vehicle, and the EV3 brick can time how long it takes to pass between them - to the millisecond! 

The program will be very simple: wait for light sensor 1 -> start timer -> wait for light sensor 2 -> stop timer -> display time

After that, I can just work it out the same way as with the video, but with extreme accuracy!

[Marxpek]

very nice idea! just don't crash into your sensors :)

[PKW]

2 hours ago, mocbuild101 said:

I think I have thought of the most accurate speed measuring possible: Mindstorms! (EV3)

I'm going to do some tests today, but I think this will be very accurate: 2 light sensors (some distance apart, with a bright torch pointing at them) will detect the passing of the vehicle, and the EV3 brick can time how long it takes to pass between them - to the millisecond! 

The program will be very simple: wait for light sensor 1 -> start timer -> wait for light sensor 2 -> stop timer -> display time

After that, I can just work it out the same way as with the video, but with extreme accuracy!

At this point using nxt and ultrasonic sensor why shouldn't be accurate?

Also in place of a torch, that diffuse a lot of light, there can be a laser maybe with the help of some nebulizer there will be also a nice effect

[Epic Technic]

11 hours ago, TechnicSummse said:

In this picture, it looks like there are tire shavings on your battery box. The tires could be ballooning outwards, causing them to rub against the battery box, slowing your car down. Maybe try mounting the battery box farther away from the tires.

[TechnicSummse]

3 hours ago, Epic Technic said:

In this picture, it looks like there are tire shavings on your battery box. The tires could be ballooning outwards, causing them to rub against the battery box, slowing your car down. Maybe try mounting the battery box farther away from the tires.

Thats what i meant...

15 hours ago, TechnicSummse said:

- look the last picture :D

Problem here is... the battery-box is mountet at the outer pinholes of the rear buggy-motors. And it fits exactly between there... moving it will mean to construct a new frame behind the rear motors, and i was intendet, to use the battery-box as frame there.

I will redesign this again

[mocbuild101]

19 hours ago, PKW said:

At this point using nxt and ultrasonic sensor why shouldn't be accurate?

Also in place of a torch, that diffuse a lot of light, there can be a laser maybe with the help of some nebulizer there will be also a nice effect

The NXT is much slower at reading sensors, it requires a more complicated program, and sound travels slower than light .

I did think about using lasers - and they would be the best thing to use - but I don't have any, and the torch I'm using can be focused into a small beam of light - so I thought that would be fine.

15 hours ago, TechnicSummse said:

Problem here is... the battery-box is mountet at the outer pinholes of the rear buggy-motors. And it fits exactly between there... moving it will mean to construct a new frame behind the rear motors, and i was intendet, to use the battery-box as frame there.

All you would need are 4 axle/pin connectors - with some pins of course!

Edited June 28, 2017 by mocbuild101

[TechnicSummse]

2 hours ago, mocbuild101 said:

The NXT is much slower at reading sensors, it requires a more complicated program, and sound travels slower than light .

All you would need are 4 axle/pin connectors - with some pins of course!

hmm wich ones do you mean? can you post partnumber or a photo please?

[mocbuild101]

10 hours ago, TechnicSummse said:

hmm wich ones do you mean? can you post partnumber or a photo please?

This:or this:or possibly both (two of each).

Edited June 28, 2017 by mocbuild101
Images disappeared...

[TechnicSummse]

As promised, i will show you finally some new pictures of the actual progress.

The weather here is pretty bad at the moment, so i could not do any testdriving in the last few days :(

Since i could not do any testdriving, i continued disassembling and rebuilding all the time. Maybe i lost some good setup like that... but i couldnt sit there doing nothing :(

So i just builded and kept the model, wich felt to be the best setup so far. Tests coming soon... not today, because it is still raining like there would be no tomorrow.

 

A so far untestet 2:1 gearing setup idea

__________________________________________________________________

Yesterdays result:

_______________________________________________________

current setup... lightened it a bit, and added the speed computer.

Gearing is 40:12 now, using just 3 gears (2x 40, 1x 12), and a total axle/beam-friction of 6x thin beam (2x at the frontwheel, 4x at the rear wheels)

Total weight now (including speed computer) is 1030g.

@Marxpek i think we will end here with nearly the same specs, since we are aiming to the same small point as goal.

I decided to make a small little video instead of some pictures, showing also the booster-switch and the steering in action.

 

Edited July 2, 2017 by TechnicSummse

[Marxpek]

Hmm i do not know if this is an improvement to your design, the profile seems much much higher now, cause more air resistance, also the battery box on top will make it more likely to start rolling, i liked your setup with it being in the back better.

I also noticed you are using long axles where you can you axle connectors, these less likely to bend under speed, https://www.bricklink.com/v2/catalog/catalogitem.page?P=6538c&name=Technic, Axle Connector 2L (Smooth with x Hole + Orientation)&category=[Technic, Connector]#T=S&O={} any reason why you are not using these?

Did you ever consider to take out the 9v switch? just switch the batterybox directly with the micro motor? would save the switch and a wire in weight.

10 minutes ago, TechnicSummse said:

i think we will end here with nearly the same specs, since we are aiming to the same small point as goal.

sounds about right, but don't forget that i will be able to fully power all 4 motors.. 

17 minutes ago, TechnicSummse said:

A so far untestet 2:1 gearing setup idea

You think this is worth testing? so wide and so many frictionpoints in it for a 2:1 gearing does not seem viable to me.

[TechnicSummse]

16 minutes ago, Marxpek said:

Hmm i do not know if this is an improvement to your design, the profile seems much much higher now, cause more air resistance, also the battery box on top will make it more likely to start rolling, i liked your setup with it being in the back better.

I had the battery-box in flat position, but this needs ~15g more weight :D

Just an idea wich needs testing like this... as i told... since i cant doing any testdriving at the moment, i am just building and building and changing and changing :D

Quote

I also noticed you are using long axles where you can you axle connectors, these less likely to bend under speed, https://www.bricklink.com/v2/catalog/catalogitem.page?P=6538c&name=Technic, Axle Connector 2L (Smooth with x Hole + Orientation)&category=[Technic, Connector]#T=S&O={} any reason why you are not using these?

I used them in ALL earlier models, but just because they were needed (because i dont have any axle beeing longer then 12 studs). In this setup i could use a 12 stud axle the first time. I dont like the connectors really, because the axleholes sometimes are not 100% straight. Another point is... since the axle goes in there just 1 stud on each side, they tend to bend even more then a well fixed axle.

Quote

Did you ever consider to take out the 9v switch? just switch the batterybox directly with the micro motor? would save the switch and a wire in weight.

Sure i did that :D

But the micromotor is not srong enough to move the battery-box-switch :(

Quote

You think this is worth testing? so wide and so many frictionpoints in it for a 2:1 gearing does not seem viable to me.

Well... my 2-motor-record racer also used this kind of setup... bearings at the motor-pinholes. This was just a 1:1 copy of my 2-motor setup, usable with 4 motors. Dont think i will ever test this... but as i told before... im just building and disassembling, to find any better idea :D

Its pretty much like a brainstorming

Edited July 1, 2017 by TechnicSummse

[mocbuild101]

58 minutes ago, TechnicSummse said:

A so far untestet 2:1 gearing setup idea

I'm going to be testing 2:1 gearing tomorrow, but with only 2 motors.

32 minutes ago, Marxpek said:

...cause more air resistance

I don't think that air resistance will slow anything down much.

19 minutes ago, TechnicSummse said:

Its pretty much like brainstorming

It's BRICKstorming .

[TechnicSummse]

22 hours ago, mocbuild101 said:

It's BRICKstorming .

:D nice word

 

I found a dry hour here, and testet my latest setup:

1036g battery-box flat mounted infront of the rear-wheels.

40:12 gearing (3 gears in total)

(pretty much the same then postet yesterday, except mounting the battery-box flat)

 

=> 36,2 kph... i guess the problem is: the 12 tooth-gear is beeing sucked between the two 40 tooth-gears and beeing impactet there, producing a lot of friction.

Also i realised... i need a longer track... i think there is some energy left, but i need to stop at the tracks end.

 

Well for now this means i have to rework the gearing again... i will go again closer to the 24:8 idea wich was the best so far.

[TechnicSummse]

After building another few hours... i have a completely new design, with a good feeling... not testet yet.

My chaos :D

 

The new design... i will call it: The Machine

~1080g

- 6 half beams at the rear axle

- just 2 gears in use (40:20)

This was a really hard way to design the 40:20 gearing while using only 1 pair of gears. I will redesign and lighten everything a little bit tomorrow :D

But im pretty sure, this could give some nice results :)

 

[mocbuild101]

Nice, but I can't help thinking that all that weight will slow it down - 1080gm is very heavy!

And you also have the same 2:1 gearing that I used in my 670gm car: - yes, you have 4 motors, but they aren't fully powered.

 

[Jurss]

Lot of mass seems behind of wheels, which will impact stability, grip not the good way. Also it will pop up the front, when starting.