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

[mocbuild101]

11 hours ago, Aventador2004 said:

I am going to use l motors.

L-motors are too slow - the required gearing would add too much friction.

9 hours ago, TechnicSummse said:

But at the end... 2 buggy-motors are cheaper then 4 L-motors.. arent they?

They are probably about the same - depending on where you buy them from.

6 hours ago, Marxpek said:

Learn from mine and others mistakes... don't break the amount of Lego i have destroyed ;D

Let's have fun and break that 40 km/h! And pray we don't send too much parts to Lego-heaven, a.k.a dustbin...

Agreed, but I will probably be doing my tests inside (I have a spot in my house that is close to 10m of smooth wooden floor), so I won't be breaking anything!

6 hours ago, Aventador2004 said:

I am not sure it will hit even 20, the friction is too much, but I am thinking:

1. 2 L motors + 1 XL motor.
2. Buy a buggy motor.
3. Collaborate with someone else (mocbuild said yes).
4. Give up.
5. buy a train motor, gear down, and go for 40!

Here's what I think:

1. like I said above, this will need too much gearing.
2. this might be an option, but 1 buggy motor will probably not be enough.
3. very good idea!
4. no way!
5. this could work, I have used train motors before - and they compare quite well to buggy motors - but they will not need gearing. (which is great!)

[TechnicSummse]

1 hour ago, mocbuild101 said:

Agreed, but I will probably be doing my tests inside (I have a spot in my house that is close to 10m of smooth wooden floor), so I won't be breaking anything!

10m? What do you wanna test on this track? :D  A pullback-racer? :D

You need ~100 m or better 150... 

But indorrf driving would solve a lot of my problems... that would be nice *dreaming*

[mocbuild101]

4 minutes ago, TechnicSummse said:

10m? What do you wanna test on this track? :D  A pullback-racer? :D

You need ~100 m or better 150... 

But indoor driving would solve a lot of my problems... that would be nice *dreaming*

10m is more than you think, although I will have to give it a boost at the start...

But the main reason why I'm doing it inside is because of the smooth surface (I do have a nice long street to test it on, but the road is very rough).

Really, the best place you could ever have to test it, is in a large enclosed space with a perfectly flat polished concrete floor.

[Marxpek]

6 hours ago, PorkyMonster said:

whereas if you go the other way - adding more motors, more power, etc., the sky's the limit!!  ok that's just my view 

True fact, but at a certain point the weight of the extra construction and batteryboxes will be more than the extra motors can push (not to mention bending axles under its weight do not turn that well...), but i never said i wouldn't try ;) Also delivering power here is a problem only the rc unit can fully power the motors, but i am using 2 units now and they already cause interference with each other sometimes.

 

6 hours ago, Aventador2004 said:

the torque can be regained through gearing. the train motor gets 300 rpm more than the buggy motor, but i can change that easily.

Not really, did you notice we are gearing our buggy motors up and not down? we are going well over 2000 rpm on the axle, your best bet would be a train motor without any gearing, but it would still lack torque i think, but if you have one available, try it! but don't buy it for this reason.

[mocbuild101]

Just now, Marxpek said:

but it would still lack torque i think, but if you have one available, try it! but don't buy it for this reason.

Train motors are quite good actually, especially if you use 2 together. They do have less torque, but they make up for it by not needing any gearing (so no loss).

[Marxpek]

2 minutes ago, mocbuild101 said:

10m is more than you think, although I will have to give it a boost at the start...

But the main reason why I'm doing it inside is because of the smooth surface (I do have a nice long street to test it on, but the road is very rough).

Really, the best place you could ever have to test it, is in a large enclosed space with a perfectly flat polished concrete floor.

10 meters? sorry to tell.. but no way... like Technicsummse sayd: 100-150m is more realistic, i will not pick a track that is under 200m long.

Finding a good road is my biggest problem as well, it's all either very crowded, rough or too short.

Let me know when you find that polished concrete slab, the best i can find is a really rough concrete road, i wish i had the concrete technicsummse has in his video, that looks smooth as ice.. But i am always scouting for a better area.

[TechnicSummse]

5 hours ago, Marxpek said:

10 meters? sorry to tell.. but no way... like Technicsummse sayd: 100-150m is more realistic, i will not pick a track that is under 200m long.

Finding a good road is my biggest problem as well, it's all either very crowded, rough or too short.

Let me know when you find that polished concrete slab, the best i can find is a really rough concrete road, i wish i had the concrete technicsummse has in his video, that looks smooth as ice.. But i am always scouting for a better area.

As you do... im allways looking for a btter track. The Penny-market parking is ok (pretty clean and flat) after 20:00 at the evening, or at sundays. But some people drive there also late at the evening, and this gave me some dangerous situations...running down the street, fully concentratet, steering your car...and boom... there is a real car infront of you... not really a nice experience.

 

Ive got a second track... wich is ~200m and flat... but this one is pretty dirty, and has a little problem... at the end, there is a wall... and as you can imagine... i hit that wall a few times. Sometimes beeing out of range to break... sometims slipped off gears were the problem :(

 

What we would need is something like that:

Edited June 27, 2017 by TechnicSummse

[Aventador2004]

6 hours ago, mocbuild101 said:

1.  
2. very good idea!
3. this could work, I have used train motors before - and they compare quite well to buggy motors - but they will not need gearing. (which is great!)

I already had a reason to get one, so it is fine, I was going to make a drift car with it, but this is a fine cause.

4 hours ago, Marxpek said:

10 meters? sorry to tell.. but no way... like Technicsummse sayd: 100-150m is more realistic, i will not pick a track that is under 200m long.

Finding a good road is my biggest problem as well, it's all either very crowded, rough or too short.

Let me know when you find that polished concrete slab, the best i can find is a really rough concrete road, i wish i had the concrete technicsummse has in his video, that looks smooth as ice.. But i am always scouting for a better area.

I have a recently fixed street in front of my house, and in the afternoon, no cars pass through.

That would allow me to make several runs down the street, and it has two straight-ish .05 mile sections.

[TechnicSummse]

17 minutes ago, Aventador2004 said:

I already had a reason to get one, so it is fine, I was going to make a drift car with it, but this is a fine cause.

I like the PF-train-idea. But again here you will need 2 to replace 1 buggy motor... meaning you need 4 to replace 2 buggy- motors.

And at philos page i found something wich could bring in another problem here:

Quote

The train motors also contain thermistor limitations. For the PF train motor, this protection trips too fast and prevents direct measure of the stalled current. These values were obtained by extrapolation.

Sounds like they could have problems with pulling some weight... 

What do they cost?

[Aventador2004]

1 minute ago, TechnicSummse said:

I like the PF-train-idea. But again here you will need 2 to replace 1 buggy motor... meaning you need 4 to replace 2 buggy- motors.

And at philos page i found something wich could bring in another problem here:

Sounds like they could have problems with pulling some weight... 

What do they cost?

I motor price: $14 + $4 s@h

I flipped a few l motors, so I have some money left over. I think one will at least get me somewhere.

[mocbuild101]

6 hours ago, Marxpek said:

Let me know when you find that polished concrete slab, the best i can find is a really rough concrete road, i wish i had the concrete technicsummse has in his video, that looks smooth as ice.. But i am always scouting for a better area.

I won't ever be finding that anytime soon, but now I think of it, there is a large parking lot near my local school that I could use - it's very smooth, and is normally empty except at school pick-up time - but it is a fair way from my house, so...

2 hours ago, TechnicSummse said:

What we would need is something like that:

-- image --

That would be amazing!

1 hour ago, TechnicSummse said:

And at philos page i found something wich could bring in another problem here:

Sounds like they could have problems with pulling some weight... 

I have never had any problems...

[Marxpek]

59 minutes ago, mocbuild101 said:

but it is a fair way from my house, so..

The track i have been using is about 10 minute bike ride away (i need my bike to follow and film the car) but i have found myself a way smoother track today at about 20 minutes of cycling, a bike-lane, it kind of looks like that polished concrete slab you are talking about and it is about 500m long and very clean!! just one big drawback: it is just 2 meters wide, not leaving a lot of room for corrections, but a good run does not need any corrections, so it would be a matter of: keep trying, it looks to be 100% flat, but my gps device will be the judge of that when i try it.

I'm hoping to try it out with my new racer later today or tomorrow, but my time (or daylight) is limited sadly..

3 hours ago, TechnicSummse said:

What we would need is something like that:

That surface would be great, but we would get higher speeds then the car can reach on its own when it comes down from the curves, the cyclists using this track use this to their advantage a lot, we need a 100% flat track.

3 hours ago, TechnicSummse said:

Sometimes beeing out of range to break...

Please don't tell me you are braking using 3 buggy motors on the rc unit and then slam it into reverse... you are gonna fry it one day... please don't..

[TechnicSummse]

1 hour ago, Marxpek said:

Please don't tell me you are braking using 3 buggy motors on the rc unit and then slam it into reverse... you are gonna fry it one day... please don't..

Uhm... yes i have to tell you this :D

[Marxpek]

Just now, TechnicSummse said:

Uhm... yes i have to tell you this :D

It will potentially damage your unit faster then stalling motors, when at full speed reversing engines i speculate/expect the current going even higher, since the forward motion is now powering the motors, turning them into generators, sending 2 currents into each other.

I'm no electrician, but to me it sounds like a bad, bad thing to do... Like putting your car in reverse on the highway...

[TechnicSummse]

1 hour ago, Marxpek said:

It will potentially damage your unit faster then stalling motors, when at full speed reversing engines i speculate/expect the current going even higher, since the forward motion is now powering the motors, turning them into generators, sending 2 currents into each other.

I'm no electrician, but to me it sounds like a bad, bad thing to do... Like putting your car in reverse on the highway...

How do you break?

The RC-unit must be strong enough to take this with 2 motors... because every simple rc-car is driven like that... breaking means reversing the motors.

At the moment a fakt is... we dont know if it is ok for the rc-unit to controll 3 motors, or it is not... i know it could be a not so good idea... but i will try to find out some further information about this... 

Im trying to find out what exactly happens, if you reverse the motors while the are running.

[Marxpek]

41 minutes ago, TechnicSummse said:

How do you break?

I don't brake, i crash, my car was more solidly built than yours so it could take a bit of a hit without "exploding" ;D my track here has grass on both sides, clearly visible in my video's, so that's a fairly safe option, otherwise just let it run it course, that why i want 200m minimum, the downside of the grass on the sides is that it too can break the front 7L liftarms i used in the steering, i broke 4-5 total i guess when driving at speed into grass.

And yes i do think the rc unit can handle reversing 2 motors, but not in the way we have geared them and with these speeds (way more force is needed to stop them, thus longer time of high current). It is very bad for the motors themselves and is always a bad idea to reverse polarity on any motor instantly especially in high torque situations. I only brake by reversing the motors when i see extreme danger to my Lego or others, like a incoming car or not being able to avoid a solid object (one side of my track has trees alongside it). 

1 hour ago, TechnicSummse said:

At the moment a fakt is... we dont know if it is ok for the rc-unit to controll 3 motors, or it is not... i know it could be a not so good idea... but i will try to find out some further information about this... 

I admire your guts for trying, it crossed my mind to try it as well, but after reading into it i decided to never try it...maybe what i read was right or maybe it was wrong, but i decided to not risk nearly 20 year old and hard to come by equipment

 But even if you fry your rc unit while doing it, it would still be a record, just make sure you film every attempt! But is that worth it knowing that someone (me) could reach similar result with a 2nd rc unit?

Did you ever manage to reach the 38+ again? Do you notice any changes? weird smells (near the antenna opening after a few runs) 

[TechnicSummse]

1 hour ago, Marxpek said:

Did you ever manage to reach the 38+ again? Do you notice any changes? weird smells (near the antenna opening after a few runs) 

No strange smellings so far... im really taking care of that :D

I can reproduce the 38+ many times with the 24:8 gearing setup like in the first post of my WIP-topic.

I am working on a 24:12 solution now, with low friction and stable bearings. But its really hard to get that combined... with my 2 wheels i need 4 bearing points (2 on each side of the wheel). With 2 motors, it was ok to have just 2 bearings (at the outer side of the wheels), but 4 motors are too heavy, and axle bends to much without an additonal bearing at the other side of the wheels.

With the 24:8 gearing at the lowspeed-output this was no problem, i could use thin beams at all 4 points. While using the highspeed-output, i can not transport the power outside the motorcase. I could use a 40:24 gearing to come outside there, but thats just a 1:1,6666 and thats way to low. And as long as i need to stay within the case, i need to use the motors pinholes as bearings... meaning 4 studs instead ot 2 studs of axle/beam friction.

I could also use a 40:20 gearing ( i love that, used it in a few trys of my 2-motor-versioin), but here also is the bearing problem. I need to use thick beams for this, because there are no angled thin beams, wich would help here :(

 

Edited June 27, 2017 by TechnicSummse

[mocbuild101]

8 hours ago, TechnicSummse said:

The RC-unit must be strong enough to take this with 2 motors... because every simple rc-car is driven like that... breaking means reversing the motors.

It can handle breaking with 2 motors, but not 3 motors (like you have).