[WIP] trying to break 40km/h with only Lego "2 new designs, -steering advice needed"

[mocbuild101]

Just now, Marxpek said:

is it a Lego tire? i could not find any that fit this pulley wheel.

As far as I know, it is a Lego tire.

Just now, Marxpek said:

It feels a little low to me, my current theoretical speed is 75,46 km/h,  @TechnicSummse racer that did 38km/h+ has a theoretical 66km/h and my first steering record with 2 motors had a theoretical speed of 57,13 km/h,  but it is very hard to say what works best, at least yours will have no problem accelerating, but my guess is you can gear it up further!

That's what I thought, but all the wheels I am using are smooth, and I currently only have it geared up 3:5 - if I change it to 1:3 (which I'm also going to test), the theoretical top speed would be about 92km/h!!!

By the way, what's the gearing you are using?

[Philo]

47 minutes ago, Marxpek said:

is it a Lego tire? i could not find any that fit this pulley wheel.

See https://www.bricklink.com/v2/catalog/catalogitem.page?id=70481#T=S&O={}

[TechnicSummse]

1 hour ago, mocbuild101 said:

By the way, what's the gearing you are using?

@Marxpek uses a 40:16 at the high-speed output with his actual racer in this topic.

I used a 24:12 at the high-speed output with my 34,8 km/h 2 motor record-car.

The actual higherst result (38,7 km/h) i could get with a 24:8 at the low-speed output. But i ve got the feeling, that the 8 teeth gearing is not the best at this use... i think a 36:12 would be better then a 24:8... but its just a feeling

[Marxpek]

37 minutes ago, Philo said:

See https://www.bricklink.com/v2/catalog/catalogitem.page?id=70481#T=S&O={}

thanks, but this is the tire we already discussed for the small pulley, we are looking for a tire on the big (old) pulley, https://www.bricklink.com/v2/catalog/catalogitem.page?id=688#T=S&O={}

i'm not aware it exists, but if it does i would like to know.

 

12 minutes ago, TechnicSummse said:

i think a 36:12 would be better then a 24:8... but its just a feeling

for sure, the 8t gear is a bit weak (my racer ate a few when i tried to make a 36:8 gearing). and since it is smaller it has a higher chance in slipping gears. (but your execution was pretty good with the 8t wedged between the 2x 24t)

[Aventador2004]

2 hours ago, mocbuild101 said:

As far as I know, it is a Lego tire.

It is, I have it. It is in the lego contraptions book, which I got it in. The pulley rubber slips on top of the wheel.

[Marxpek]

8 minutes ago, Aventador2004 said:

It is, I have it. It is in the lego contraptions book, which I got it in. The pulley rubber slips on top of the wheel.

do you have a partnumber or any other information on it?

[Aventador2004]

14 minutes ago, Marxpek said:

do you have a partnumber or any other information on it?

I can check,

4185 is the part number, the rubber, not sure. It is in 9467 too.

[Marxpek]

Sorry but again, this is the tire for the small pulley wheel, we are looking for the tire that was used on the big pulley wheel  https://www.bricklink.com/v2/catalog/catalogitem.page?id=688#T=S&O={} in the picture @nerdsforprez sent.

[technic_addict]

If I had the talent to build something I would try and build a simple gear box which switches from the low RPM shaft to the high RPM shaft.  I would think you can then gear even faster since the low RPM shaft has overcome the torque issue at low speed.

[Marxpek]

1 minute ago, technic_addict said:

 

If I had the talent to build something I would try and build a simple gear box which switches from the low RPM shaft to the high RPM shaft.  I would think you can then gear even faster since the low RPM shaft has overcome the torque issue at low speed

 

I have tried this, but it would either need a much more gears or poorly braced gears, (in both cases adding a lot of friction) i'm not saying it cannot be done, but from my experience: simplicity is key here, but maybe i will give it a try again, i do love the idea.

[nerdsforprez]

7 hours ago, Marxpek said:

thanks, but this is the tire we already discussed for the small pulley, we are looking for a tire on the big (old) pulley, https://www.bricklink.com/v2/catalog/catalogitem.page?id=688#T=S&O={}

i'm not aware it exists, but if it does i would like to know.

 

for sure, the 8t gear is a bit weak (my racer ate a few when i tried to make a 36:8 gearing). and since it is smaller it has a higher chance in slipping gears. (but your execution was pretty good with the 8t wedged between the 2x 24t)

It is not a tire but a rubber band.  I no longer have the put assembled, and I cannot remember if the band was official Lego or not.  But I think the large, blue Lego rubber band fits this large pulley just fine....

[TechnicRCRacer]

Here you go:

https://www.bricklink.com/v2/catalog/catalogitem.page?P=x137&idColor=11#T=C&C=11

[PorkyMonster]

 Looks like you guys are going from already-quite-small wheels to even more flimsy options...

I always thought that if we're relying on sheer engine (*ahem* motor) power, then the lighter the wheels the better... however, if we want to build up momentum and accelerate gradually over a long distance, then larger wheels are better since they'll store energy and keep going with less and less "push".

[mocbuild101]

2 hours ago, nerdsforprez said:

It is not a tire but a rubber band.

2 hours ago, TechnicRCRacer said:

Here you go:

https://www.bricklink.com/v2/catalog/catalogitem.page?P=x137&idColor=11#T=C&C=11

That is not it, it is a tire that is very similar to a rubber band.

Have a look at the bottom of this page: https://www.bricklink.com/catalogItemInv.asp?B=9781591747697

You will see the note: "Missing 2x O-Ring shown in parts list"

That is the part that fits over the large pulley.

So I will create the Bricklink part myself (because I have it), and then request an inventory change - although this will take a few days.

 

Problem solved!

 

 

[TechnicSummse]

10 hours ago, technic_addict said:

If I had the talent to build something I would try and build a simple gear box which switches from the low RPM shaft to the high RPM shaft.  I would think you can then gear even faster since the low RPM shaft has overcome the torque issue at low speed.

@Sariel built a simple solution for this:

http://sariel.pl/2011/06/rc-motor-output-selector/

But as @Marxpek wrote, you will have a lot of additional friction here... 11 times a axle-pinhole-friction, just at this. (we try to reach a maximum of 2-4 axle-pinhole-friction in the whole model)

 

12 hours ago, Marxpek said:

for sure, the 8t gear is a bit weak (my racer ate a few when i tried to make a 36:8 gearing). and since it is smaller it has a higher chance in slipping gears. (but your execution was pretty good with the 8t wedged between the 2x 24t)

My feeling is more, that beacause of the verry low radius of it, the axle will be pulled up or down more by the driving gear (and like that be pushed at the pinhole, producing friction), instead of beeing rotatet smoothly.

 

I tried a new idea with my model now... but same problem as @Marxpek its a bit wet outside :D 

I cant testdrive at the moment :(

I will post some pictures in my topic at the evening :)

Edited June 30, 2017 by TechnicSummse

[Marxpek]

2 hours ago, mocbuild101 said:

That is not it, it is a tire that is very similar to a rubber band.

Is it similar in design to the small pulley tire? or is it softer like a rubber band?

At the moment i have put 2 small pulley wheels with rubber tire in my front end (kind of hard to get 1 centered on a axle..), roll resistance is very low, but i fear it will be too bumpy on the road outdoor, and it has just half a stud of ground clearance, which i don't really like, I will try though.

39 minutes ago, TechnicSummse said:

My feeling is more, that beacause of the verry low radius of it, the axle will be pulled up or down more by the driving gear (and like that be pushed at the pinhole, producing friction), instead of beeing rotatet smoothly.

That is also true, but the small radius also means there is less tooth-to-tooth contact, putting more torque on a single tooth compared to bigger gears, making it easier to slip and/or destroy the teeth.

1 hour ago, TechnicSummse said:

tried a new idea with my model now... but same problem as @Marxpek its a bit wet outside :D 

I cant testdrive at the moment :(

I will post some pictures in my topic at the evening :)

Yeah weather is a pain at the moment...

I have changed the front end a little bit (lost the brace, might indeed be better in case of a crash, so the front can "split open"), and added some outrigger axles as protection, and some minor tweaks, i'll make some pictures on the updated version today as well, might even do another run to test the pulley wheels.

And i'll be looking forward you see your new (crazy? ;D) idea!

[mocbuild101]

37 minutes ago, Marxpek said:

Is it similar in design to the small pulley tire? or is it softer like a rubber band?

It is thinner than the small pulley tire (2mm round cross section), but it is the same hardness - not soft like a rubber band.

40 minutes ago, Marxpek said:

Yeah weather is a pain at the moment...

Same here!

But I did manage to get a few tests in today, so will be starting a WIP topic soon...

[nerdsforprez]

5 hours ago, mocbuild101 said:

That is not it, it is a tire that is very similar to a rubber band.

Have a look at the bottom of this page: https://www.bricklink.com/catalogItemInv.asp?B=9781591747697

You will see the note: "Missing 2x O-Ring shown in parts list"

That is the part that fits over the large pulley.

So I will create the Bricklink part myself (because I have it), and then request an inventory change - although this will take a few days.

 

Problem solved!

 

 

Oh that is awesome - problem is solved!  At first I thought you were trying to indicate that the rubber band (square cross section) was it when clearly it is not.  But I reread and yes..... it looks exactly like an O-ring and currently it is NOT a part on BL so I thought that I had gotten the O-ring from somewhere totally different.  Thought it to be Non-Lego.  Guess not......great news!

[Marxpek]

38 minutes ago, mocbuild101 said:

It is thinner than the small pulley tire (2mm round cross section), but it is the same hardness - not soft like a rubber band.

Will you be using/testing it in your racer? 2mm seems rather small to me.

I have just done few testruns and my gps data show a fairly consistent difference: the (2) small pulley wheels always took more track and time to reach the same speed compared to one 36.8 x14 zr (although all my runs ended in crashes).

I have also destroyed a 40t gear with a crash, a good section of the teeth has been grind down when i got on the edge of my new track..., ending the tests for today.

[TechnicSummse]

 

Quote

I have also destroyed a 40t gear with a crash, a good section of the teeth has been grind down when i got on the edge of my new track..., ending the tests for today.

 

I'm sorry to hear that :(

1 hour ago, Marxpek said:

Will you be using/testing it in your racer? 2mm seems rather small to me.

I have just done few testruns and my gps data show a fairly consistent difference: the (2) small pulley wheels always took more track and time to reach the same speed compared to one 36.8 x14 zr (although all my runs ended in crashes).

3 hours ago, Marxpek said:

At the moment i have put 2 small pulley wheels with rubber tire in my front end (kind of hard to get 1 centered on a axle..), roll resistance is very low, but i fear it will be too bumpy on the road outdoor, and it has just half a stud of ground clearance, which i don't really like, I will try though.

 

As i told few days ago... this will be fine indoor, but doesnt work outdoors. I testet this wheel allready:

And it was allready way to bumpy...

-> since we dont use any suspension, we need rubber at the wheels. Also the radius is to small... it will get stuck on verry small stones on the road. That's the reason why you meassure slower speeds here, compared to your other wheel

 

3 hours ago, Marxpek said:

And i'll be looking forward you see your new (crazy? ;D) idea!

Nothing really spectacular... just another frame/gearing-setup.

I geared 40:12 at the low-speed-output now, but using just 3 gears in total. At the moment i use 6x (could be reduced to 4) thin beams as bearings with this... 2 on each side of the gear, and 2 on each side of the wheels... (just a half bush as space-holder on each side).

So there should be close to no axle-bending

But i will show this at the evening :)

Edited June 30, 2017 by TechnicSummse

[Marxpek]

1 hour ago, TechnicSummse said:

 

I'm sorry to hear that :(

Don't worry, i grew used to this kind of damage :D, just sad in ended my tests.

 

1 hour ago, TechnicSummse said:

As i told few days ago... this will be fine indoor, but doesnt work outdoors

well the difference is very minimal, don't forget that the pulley wheels are way more narrow so less likely to hit small stones, but if they do, the impact is harder, and on the small pulleys the tires are a bit bigger then 2 mm (i guess 4 mm) in the end it all depends on the track. 

1 hour ago, TechnicSummse said:

I geared 40:12 at the low-speed-output now, but using just 3 gears in total. At the moment i use 6x (could be reduced to 4) thin beams as bearings with this... 2 on each side of the gear, and 2 on each side of the wheels... (just a half bush as space-holder on each side).

I too have only 4 half beams of friction in my rear setup with no bending of any axles, it can spin without load, without bending the axles (spinning it without load is a pretty good test for that i think, you will see the wheels start to wobble if the axles bend under speed/high forces)

Front setup has been changed after today's test, basic principle is the same just lighter.

I haven't been able to get the max speed from my current gearing yet (looking at the gps data speed graphic is so helpful here), all 4 runs ended with crashes or steering errors today, my new track is really smooth and long, but it is a bit too narrow, would hate to abandon it but i might have to..

Edited June 30, 2017 by Marxpek

[mocbuild101]

4 hours ago, Marxpek said:

2mm seems rather small to me.

Yes, especially when more than half of it goes into the groove of the pulley!

[Marxpek]

Little update with pictures: 

Today the weather was somewhat decent, so i decided to test out my new track, it is very smooth and clean, but it is very narrow because it has a raised center, dividing the 2 bike-lanes.

The track is long, smooth, flat and clean, but a bit narrow and the middle raised part, shown on the right picture.

After only 4 runs i ran into the middle landing on top of it partially and destroying a good section of a 40t gear, ending the test for today.

I have been using this setup today:

 This picture has been taken after driving into the middle part, you can see the grey smooth pin, totally grind down, it had a mini wheel on it before the run, that is gone with the wind.

I have been able to compare the pulley wheel + tire to the 36.8x14 ZR wheel, differences are minimal but the bigger and wider ZR wheel performs better because it is just too bumpy.

Back home i had set out to reduce the weight of the front steering section which was over-designed like i always seem to do,

I quickly simplified the front with the ZR wheel but when checking in at here at my topic i saw this:

9 hours ago, TechnicSummse said:

since we dont use any suspension

And i figured: pulley wheels and suspension could work, maybe even better, worth a try.

So i came up with 2 new front ends, yet to be tested outdoors at high speeds

(sorry for weird picture format, having a fight with bricksafe here...)

Surprisingly the suspended version with the pulley wheels weights in 1 gram less than the not suspended ZR wheel, indoor tests show good results with both setups, in theory the pulley wheel should perform better, lets see what the reality says. Fingers crossed for good weather.. 

[TechnicSummse]

1 hour ago, Marxpek said:

Surprisingly the suspended version with the pulley wheels weights in 1 gram less than the not suspended ZR wheel, indoor tests show good results with both setups, in theory the pulley wheel should perform better, lets see what the reality says. Fingers crossed for good weather.. 

Nice idea with the suspension... i would be glad if i had so much parts, just to pick out of them :O

Seems like you have every part wich you need... just grabbing into your chest and pulling it out :D

 

Why you dont put the pulleys directly together on the axle? I think its way more fragile, the way you have done it now.

By the way... bending the antennas is not a good idea... i tried it also... you will have like 80% less range. It looks nice, maybe helps a bit with air resistance, but your range is going down close to zero :(

________________________________________________________________-

Your new track seems verry nice... i have a similar track, but what are you doing with the bikers? I tested on our bike-road once, and decidet that its way to dangerous, a bike could kill my car.

What's your total weight with the actual setup?

I will post my new pictures tomorrow... im too tired now to upload them :O

Edited June 30, 2017 by TechnicSummse

[Epic Technic]

As a man of science, I'm here to tell you that you're using the wrong front wheel!

Since this wheel is not powered, we want the largest front tire to reduce friction. Plus you want to use the skinniest tire possible, to lower friction even more, but this does come at the cost of worsening your steering.