[MOC] Tractrike RC2 Record Racer 35 km/h+

[Marxpek]

Hello everyone,

here is another attempt of mine to improve the speed record, 

i have just done the first test runs and managed to get it up to 32,71 km/h, which already is an improvement to my previous record of 28,47 km/h with a single rc-unit,  but there is more power left. when i find more time and a better track i hope to squeeze a bit more out of it.

This thing has 2 rc-units on the same channel, all 4 motors are hard-coupled and geared up 1:2,5 on the single drive axle, spinning the trac 5000 tire at insane speeds.

The test run was measured with a bryton 100e gps device and also caught on film, but sadly the car is not in the shot most of the time, i'm cycling, filming and steering the car all at once, which is kind of hard, but when i find more time i will try to push it a bit further and hope to get a better shot (or way to shoot it, if anyone has suggestions how to film i would be glad to hear, here is a picture of my current setup)

UPDATE: 

the design is final with only a bit of weight reduction done, at the top of this original post you can find my new video of it going over 35 km/h.

 

 

Edited June 17, 2017 by Marxpek
update and video added

[mocbuild101]

Wow! 32.71 km/h!!! I didn't know that Lego could go that FAST!

2 hours ago, Marxpek said:

any tips on how to embed videos from bricksafe?

I was actually going to start experimenting with that... but if you have a YouTube channel, why don't you use that?

[Marxpek]

13 minutes ago, mocbuild101 said:

but if you have a YouTube channel, why don't you use that?

I want to reserve my youtube channel for complete video's, so i don't want to post clips like this there. Uploading to bricksafe is no problem just embedding them doesn't seem to work, or i'm doing something wrong.

21 minutes ago, mocbuild101 said:

 

Wow! 32.71 km/h!!! I didn't know that Lego could go that FAST!

 

And yes 32,7 km/h surprised me as well, my aim was to go over 30 and on my 3rd run i already managed well over this. 35 km/h will be the next goal i suppose, looking at the gps data curves it looks doable..

[Epic Technic]

Wow this is crazy! Can't wait to see more. What you could do is to upload the video onto your YouTube channel as unlisted so only people with the link can see it.

[Marxpek]

Just now, Epic Technic said:

What you could do is to upload the video onto your YouTube channel as unlisted so only people with the link can see it.

Thanks, i was not aware that this was possible, i'll see into that.

And yes it is kind of crazy, i really fear this setup can destroy one of the 2 rc-units, when i forget to turn one on, the unpowered motors will act as generators, sending current the wrong way into the rc-unit that is not on, i have no idea if this can damage it, but it sounds like a bad idea, but it can hardly accelerate on 2 motors, so that issue is only present without load i suppose..

[Leonardo da Bricki]

Impressive record!

To aid your filming abilities, perhaps find a partner-in-crime.  And an empty parking lot works great... 

[Marxpek]

1 hour ago, Leonardo da Bricki said:

And an empty parking lot works great

This has proven to be very hard to find near me... but i'll keep my eyes open.

[Jurss]

That tractor tyre is not the best for speed. Maybe for traction and acceleration at the beginning, but not for speed ... Even some doubled motorcycle (even motocross) tyre would be better.

[Jurss]

Made some calculations (hoping correct). With some realistic gear ration 1:2 , some speed close to 50km/h is possible.

[MattL600]

Amazing job!

[Marxpek]

1 hour ago, Jurss said:

That tractor tyre is not the best for speed

In theory this is correct, but in practice i found this to be the best tire for a few reasons:

- it is relatively wide helping with stability

- It is more "round" than the motorcross tire, this one gives a way more bumpy ride and cross tire is too loose around its rim.

- it has more traction than a slick motor tire ( i do not own 3, i will try when i get 1 extra, but the tractor tire can already loose traction on a slick surface with this amount of power)

- the tractor tire sits very tight around the rim, all other tires get loose under high centrifugal forces (with 4 buggy motors even the tractor tire wants to come off the rim when spinning freely, but crossmotorcycle tires do this way worse)

- any other tire is at least 6% smaller in circumference, meaning you will need more rotation of the axle, meaning more resistance as well.

 

I have tried and tested several setups and always ended up using the tractor tires, they just give me the best result, but i challenge you to improve this, i always like healthy competition, drive people to greater heights! 

1 hour ago, Jurss said:

 

Made some calculations (hoping correct). With some realistic gear ration 1:2 , some speed close to 50km/h is possible.

 

I would love to see these calculation, but it sounds as if these are theoretical speeds without load.

[mocbuild101]

Just now, Marxpek said:

I would love to see these calculation, but it sounds as if these are theoretical speeds without load.

Agreed, I would normaly take about 20% off just because of the gearing - which would mean about 40 km/h might be possible.

 

2 minutes ago, Marxpek said:

- any other tire is at least 6% smaller in circumference, meaning you will need more rotation of the axle, meaning more resistance as well.

I think the motorbike tires (the same ones as on the front of your car) are actually slightly bigger than the Claas tire... 

[Marxpek]

Just now, mocbuild101 said:

I think the motorbike tires (the same ones as on the front of your car) are actually slightly bigger than the Claas tire...

The motorcycle tire is 92,4mm and the claas tire is 107mm, meaning the circumference is about 14% smaller in the slick motorcycle tire.

[Jurss]

6 minutes ago, Marxpek said:

but in practice i found this to be the best tire for a few reasons:

OK, nice job.

I once noticed, that on the some same mold rims hold same mold better, other not so good. I don't remember, problem was in tyres or in rims. I have to look for it. All tyres and rims was almost the same age, there was no wear. I'll try to find.

Maybe in this case also, some rims with the same mold would hold better, or vv.

[mocbuild101]

Just now, Marxpek said:

The motorcycle tire is 92,4mm and the claas tire is 107mm, meaning the circumference is about 14% smaller in the slick motorcycle tire.

Oh... I didn't know that the Claas tire was that big!

Note to self: get Claas tires .

Edited June 5, 2017 by mocbuild101

[Jurss]

Found that topic

problems was with newr tyres, which used some kind of other rubber, that slipped around rims, or the mold of tyres was different, so that they made not so good contact with rims.

[mocbuild101]

3 hours ago, Jurss said:

problems was with newr tyres, which used some kind of other rubber, that slipped around rims, or the mold of tyres was different, so that they made not so good contact with rims.

So that's why some of my tires are a bit slippy... especially my 42037's tires!

[Jurss]

I just noticed, that i gave there wrong set number, not 42027, but the other set was 42029.

[Marxpek]

9 hours ago, Jurss said:

problems was with newr tyres, which used some kind of other rubber, that slipped around rims, or the mold of tyres was different, so that they made not so good contact with rims.

The only tires i have considered using here are the motorcycle tires (cross and slicks), the claas tire and the 94.8mm balloon tire, the last one slips like a maniac so that one dropped off soon, but i have not checked different types of rubber, i'll check if i can find differences.

Edited June 5, 2017 by Marxpek

[Zerobricks]

Nice speed! Maybe you could get higher speed by using the yellow ring pieces from BWE as drive wheel. Sure, traction will be poor and they will get damaged, but the rolling resistance will be much lower and diamater much higher.

Edited June 5, 2017 by Zero (Zblj)

[Marxpek]

5 minutes ago, Zero (Zblj) said:

using the yellow ring pieces from BWE as drive wheel

that sounds like a fun thing to try! but i wonder if all connections that i will have to make within this "wheel" to fortify it, will hold with all this force.

Do you happen to know the diameter of an assembled ring? 

[Zerobricks]

Just now, Marxpek said:

that sounds like a fun thing to try! but i wonder if all connections that i will have to make within this "wheel" to fortify it, will hold with all this force.

Do you happen to know the diameter of an assembled ring? 

Don't have those pieces, so don't know diameter... Gotta get some though!

[Aventador2004]

54 minutes ago, Marxpek said:

Do you happen to know the diameter of an assembled ring? 

22x22 studs is the dimensions.

[Marxpek]

@Aventador2004 thanks for that info.

@Zero (Zblj) that means that wheel would "only" be 65% bigger in circumference, meaning it would still need gears to reach similar speeds, not to mention the increase of the frame and weight. i think i will pass, fun idea though! ;)

[Aventador2004]

Just now, Marxpek said:

@Aventador2004 thanks for that info.

@Zero (Zblj) that means that wheel would "only" be 65% bigger in circumference, meaning it would still need gears to reach similar speeds, not to mention the increase of the frame and weight. i think i will pass, fun idea though! ;)

maybe for a drift version?