[TC11] The Mould

[Eddie_Young]

The Mould is meant to be the hollow container used to mould things. Not to be confused with the furry green growth on your yoghurt. 

Please check out my Wind-up Robot project!!! It really walks, powered by springs! 

I always enjoy the fact that LEGO elements are very light. In this case however, it is hard to get any mass into the weapons....and mass is needed for kinetic energy. The only really heavy elements I can use are loaded battery boxes. But then...adding batteries that don't power anything would add unnecessary weight to the whole robot which would slow him down and make him less manoeuvrable. 

I don't wish to use too many motors because I have learnt that adding more than one L or XL motor to a single PF IR output results in both of those motors being slowed down and adding more batteries makes the robot less manoeuvrable for it's weight.....

In light of the two previous arguments I have decided to make a design that actually uses the chassis as a weapon. The idea is that I put all the power I can into the drive and use skid steering. Running the motors in opposite directions will then make the entire robot, with all it's weight, spin at high velocity...I shall call this 'The Dervish' and that's the signature move of my bot .

I shall use two battery boxes, each box will be equipped with a PF IR receiver and each receiver will power one L and one XL motor (I only have two of each of those motors  and that's it for motors). I will combine the outputs of the L and XL motors through differentials, thereby getting the average of there speed and the sum of there torque on the other end...by doing so, I avoid having to equalize there speeds through more complicated gearing. 

I know what your thinking......I'm trying way too hard to make this robot fast...I'll never be able to control it...... But that's the beauty of my grand design!!! The differentials act as a sort of simple gearbox...by running only one motor, I will get around half the speed but with twice the torque of that one motor!!! By running the two motors in opposite directions I shall receive a speed equal two the the difference between the L and XL motors' speeds divided by two (this last one will have very little torque however.....this is all given by the original equation for differencials....I can explain further if anyone's interested). So basically....I can go super fast with plenty of power, but I can also choose two different medium speeds (running only L or only XL motors) or a useless, sluggish, powerless speed which might be usefull for aiming and subsequent ramming at high speed  .

"Oh stop talking and start building, idiot".....okok, bear with me 

The other reason, I like this I idea, is that it has no moving parts (except the wheels that is). So there's nothing that could snap of easily and nothing loose to make it shaky. Durability is probably the greatest strength of my robot (demonstrated in the video)...It is quite simply a fast block of plastic.

Construction:

So I made two versions which I then took appart because I thought I could do better in durability and/or functionality...this is the nicer one of those two:

I'm only going to show the work in progress photos of the final version. 

So....I started with the gearbox:

        

All motors are geared up to 1:1,67 (12:20) before they enter the differencials...SPEEEEEEEEED

I already had some idea of how I'd like to make this bot durable (this is my 3rd try)....I tried to brace all the important elements with these frame-like bricks because I know they won't fail me. The video will show this guy's great durabilty. 

        

Notice that the motorcycle wheels' diameter is greater than the height of the robot, so it can run upside down. I chose the motorcycle wheels over the ones used in the first photo because they're thinner and therefore have less friction when turning. (traction is still more than adequate)

Lastly, I added a battery box on each side as far off center as they could go to still fit into 45 studs. This is to gather as much momentum as possible when spinning while not increasing the weight. I then added some reinforcements all over the chassis as well as some bodywork to make it look nice and a couple weighted bricks to balance the chassis....I don't want energy too be lost through vibration when spinning so balnce is paramount.

 

I also rebuilt the controller to make it easier to control the individual motors as I explained earlier. And took that opportunity to make it more ergonomic. 

I'll only post the video into the entry topic...it's not ready yet.

Thanks for reading. Hope you enjoyed.

Edited April 20, 2017 by Eddie_Young

[agrof]

Very cool one, I like the ideology behind, and despite the simplicity there is still a technical tweak in it. 

Don't forget to add [TC11] to the title of the topic.

[Eddie_Young]

Oops  thank you, agrof

[Eddie_Young]

There we go 

I know it's a bit cheesy... 

[TechnicRCRacer]

Very cool and clever! Extremely robust!

[PKW]

Nuts guys would be proudisplayed of you! Just a question, if you activate only the xls then the power is limited by the L motors resistance while unpowered right? Because differential always redirect the torque and so of you require more torque than the one of an unpowered L you get that that motor will be turned by the xl and all this reduces torque and speed... right? 

All this was only to be sure to know how that mechanisms works, because I see that you actually don't need torque because you have a destructive signature move and so the fine control-low torque option will be really col to maneuver that, also considering that you can achieve different tuning radius (for example by going forward with one L and one XL you don't pivot but get a curve) and this is awesome because you are actually reducing the gap between sbrick control and lego IR control

 

Also really good use of 2 battery boxes and 4 motors (you haven't created a notorspam robot) congrat!

 

ps: Have you measured your bot rpm? Either theorical or by registering the sound of it hitting something while rotating and then count hoe mamy rotations it does I'm a second? Because if it rotates at more than 500rpm then, for the UK robot wars rules, you have a spinner robot!

 

Edited April 15, 2017 by PKW

[Eddie_Young]

14 minutes ago, PKW said:

Nuts guys would be proudisplayed of you! Just a question, if you activate only the xls then the power is limited by the L motors resistance while unpowered right? Because differential always redirect the torque and so of you require more torque than the one of an unpowered L you get that that motor will be turned by the xl and all this reduces torque and speed... right? 

All this was only to be sure to know how that mechanisms works, because I see that you actually don't need torque because you have a destructive signature move and so the fine control-low torque option will be really col to maneuver that, also considering that you can achieve different tuning radius (for example by going forward with one L and one XL you don't pivot but get a curve) and this is awesome because you are actually reducing the gap between sbrick control and lego IR control

 

Also really good use of 2 battery boxes and 4 motors (you haven't created a notorspam robot) congrat!

 

ps: Have you measured your bot rpm? Either theorical or by registering the sound of it hitting something while rotating and then count hoe mamy rotations it does I'm a second? Because if it rotates at more than 500rpm then, for the UK robot wars rules, you have a spinner robot!

You are exactly right, that's why there's more torque on only Ls....XLs have more resistance when not powered.

I actually thought of this mechanism using EV3 motors (big and small ones), which can be stalled....I even got more torque from the second speed with those!

I calculated theoretically and arrived at 300 rpm and then measured from videos and found 350 rpm... The theoretical speed it should reach in a straight line is 18 km/h but I don't have enough space in my room to test :D

Edited April 15, 2017 by Eddie_Young

[Eddie_Young]

I actually thought of using worm gears, because they only let power in from one direction....but then I'd have to gear back up and I'd be losing power in friction.....I thought that's not really important since I'm really just looking for speed 

But I'm just saying....it is possible to make a three speed gearbox like this...I find it nice

 

52 minutes ago, PKW said:

Also really good use of 2 battery boxes and 4 motors (you haven't created a notorspam robot) congrat!

What is notorspam robot? 

[PKW]

1 hour ago, Eddie_Young said:

What is notorspam robot? 

ops sorry i meant "motor-spam" is like if you receive a visual spamming of motors like other big entries have (4 xls on the regicide, plenty of L motor on son of aminch and so on) instead if someone looks at you robot form the exterior and from the driving performances it looks like there is some overpowered motor or some really complicated gearing, but there is like a good surprise to see 4 motors and the right gears combined to form a really efficient mechanism

PS: the "motorspam" word come from my gaming slang, i haven't found anything to explain that but i found a lightspam example

[Eddie_Young]

nice