[MOC] Drift Wagon

[Attika]

Hello people of EB,

Let me share my drift machine with you.

It is the result of a long experiment in which I've been trying to figure out the recipe for the ultimate drifting experience. But let's start at the beginning:

My first attempt was a RWD car as we all picture a drift car should be. And however it was capable to make doughnuts I was missing the proper handling, where coming out from an arc can be predicted, or even intended. Sadly I did not make a video about the first version, but drove me to the conclusion that the handling can be improved by extending the wheelbase. So the next version I've built longer and it verified my assumption, the handling has improved, yet came nowhere close to the level I've aimed. Lucky for us I made a video at this stage:

https://www.flickr.com/photos/141631433@N07/33446568771/in/album-72157678342432663/

This car had a fairly simple build, using only 1 Rc buggy motor coonected directly to the rear differential, and a servo for steering. As power souce I've been using RC LiPo's (500mAh 25C). I know that divides the community not being approved by the church, but since I discovered it's pro's I'm addicted to them. Small size, low weight, yet capable to feed the buggy motor(s) trough Sbrick.  This version of the car was around 720 gramms and I think this is a very friendly number on the scale in therms of a fast and agile vehicle. 

The Rc wheels I'm using on it have rubber tyres, but thanks to the low weight it could spin them without any additional preparation. Using them though is my personal obsession due to their geometry and aesthetics, has nothing to do with drifting abilities.

Still I was missing the elongated arcs and the predictible behaviour. The only bottleneck I had was the controll. Touchscreen controlers drive my mad, not giving any physical sense about what am I doing. Imurvai's application for game controllers was like an oasis in the touchscreen desert for me. (God bless him). But even the physical controller couldn't give me that smooth controll on throttle what I wanted to keep the wheelspin on the border of loosing or keeping the traction. (does this make sense to you?) God I was missing the throttlecurve from my heli controller. :-) So a different approach needed and the idea came that 4 wheel drive should give me the last piece of the puzzle. In my theory the driven front wheels are pulling the vehicle in the choosen direction, while I have to admit this changes the overall behaviour too. So I've built the 4x4 version of that estate car:

And after a few modification and addition I've achived the controlled skiding I was looking for. 

All wheels being driven the traction had to be lowered as 1 buggy motor/axle wasn't enough to make the tyres spin. Instead of using plastic wheels I 've picked my favorite tool: insulation tape. And here is why:

Plastic wheels have so low friction on wood like driving on ice. I was gonna loose all the handling I was working for. The tape in the other hand gives considerably more friction/traction even if all the tyre is covered. But it isn't. By carefully choosing the right width of the tape let us fine tune the traction giving the ability to change between oversteer and understeer on demand, or deciding how "happy" the tail of the car we want it to be. 

On more benefit of the tape on the front wheels: If ther is a caster on the front, when it turns to any direction the wheels are tilting too, touching the floor only with their edge. As the edge is not covered by tape, so the rubber comes to contact, giving more traction when changing direction. And when the steering goes straight the traction lowered to the amount we set up by the tape so the wheels can skid and spin.

And there is a subjective reason as well: plastic wheels are noise too.

To improve agility I needed a handbrake too. The video gives a straight-forward explanation about it, I think it is qiute self explanatory stuff. The setup has enough power to stall the buggy motor. While I admit it's not "healty for the all parts, we have to accept: Every magic comes with a price. 

4 motors and 4 LED's required 2 Sbrick to controll them.

I think that is it so far. If I forgot to cover something, please feel free to ask about it, but let me point out I can't do much about being non purist. This is about engineering for me, not about religion. So anything regarding this subject will be answered by 1 minute of silence  

There are more pics in the Flickr gallery: 

https://www.flickr.com/photos/141631433@N07/albums/72157678342432663

Hope it was usefull for future drift projects

Your comments are wellcome

Attika

Ps: Part of this subject I've posted the other day in an old topic started by rm8 in 2012. It what was digged up by a new member and finding that topic on first page made me share my fresh experiences without checking the date on the question. Hereby I apologise doing silly things like that. 

[nerdsforprez]

Couple of things....

1 - Ken Block would be so proud. 

2- your sins are forgiven

3- The brake mechanism is so cool!  Not sure I have seen it before in a Lego Drift car. Most Lego versions appear to solely rely on motor strength for drifting 

[tibivi]

This is just awesome. I know how hard it can be to get a lego car in this scale actually drifting within control of the driver.
Also  most of the drift moc's I've seen only slide or just spin around. But this is actually thought out and it shows.

I will probably try to reverse engineer it to learn from it.

Can I ask what RC wheels those are, and I really like the mounting solution. 

Tibivi

[Attika]

23 minutes ago, nerdsforprez said:

Couple of things....

1 - Ken Block would be so proud. 

2- your sins are forgiven

3- The brake mechanism is so cool!  Not sure I have seen it before in a Lego Drift car. Most Lego versions appear to solely rely on motor strength for drifting 

1. He has to bring down a tower to reach up to me....

2, thank you "Your Holiness"  

3. even the real ones can't make it without handbrake. But as I said, that ruber ++ part has got worn after extended use. "viva la bricklink" 

13 minutes ago, tibivi said:

This is just awesome. I know how hard it can be to get a lego car in this scale actually drifting within control of the driver.
Also  most of the drift moc's I've seen only slide or just spin around. But this is actually thought out and it shows.

I will probably try to reverse engineer it to learn from it.

Can I ask what RC wheels those are, and I really like the mounting solution. 

Tibivi

Thanks. I'll make pictures when tear it down, and will post the link here for them.

Lin for the rims:

http://www.ebay.co.uk/itm/152272696375?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[agrof]

Very cool looking wagon (RS6?), and clever brake system! 

[Attika]

6 minutes ago, agrof said:

Very cool looking wagon (RS6?), and clever brake system! 

Cheers. I did not pay much attention on specific details so I'm not brave enough to name it despite the logo's, but if we have to think about 4 wheel drive wagon, Audi comes first for me.  

Edited April 3, 2017 by Attika

[TechnicRCRacer]

Amazing! Looks so fun! Is the 3D printed U-joint file available anywhere? I like the body detail in this MOC!

[Saberwing40k]

Very nice. My only gripe is the doors. I know you're worried about weight, so that's why you don't have them. So, I was thinking that a flexible axle going from the bottom of the windshield to the C pillar would complete the outline of the door, as this model looks very much like a wireframe already, and that would complete it.

[Leonardo da Bricki]

Awesome wagon! Drifting ability is great, brakes are genius, and it looks pretty good!

[1gor]

15 hours ago, Attika said:

Cheers. I did not pay much attention on specific details so I'm not brave enough to name it despite the logo's, but if we have to think about 4 wheel drive wagon, Audi comes first for me.  

that was obvious at the first sign - "Avant" model with 4 Olympic rings (now in white) and car manufacturer that made probably best 4 wheel drive - Quattro  

now I realized that you made also one more great  thing - special universal joint with axle . Why didn't LEGO make such universal joint...

[Attika]

16 hours ago, TechnicRCRacer said:

Amazing! Looks so fun! Is the 3D printed U-joint file available anywhere? I like the body detail in this MOC!

It is my own design, but uploaded onto shapeways. I've checked and somehow it isn't available there, so I'll dig it up and share the 3d file here.

 

12 hours ago, Saberwing40k said:

Very nice. My only gripe is the doors. I know you're worried about weight, so that's why you don't have them. So, I was thinking that a flexible axle going from the bottom of the windshield to the C pillar would complete the outline of the door, as this model looks very much like a wireframe already, and that would complete it.

 You got me on this.... I have to admit I could have patch it some way, but every attempt I had was spoiling the shape, so I've decided to leave it without doors. As a drift car it wasn't relevant for me anyway  and I grabbed the first thing I could find to blame it on: weight.   Still the other end of this project is still open, there will be a non motorised version and I can promise that I won't be left without doors. Here is a WIP picture of it:

 

11 hours ago, Leonardo da Bricki said:

Awesome wagon! Drifting ability is great, brakes are genius, and it looks pretty good!

Thanks Bro 

 

2 hours ago, I_Igor said:

now I realized that you made also one more great  thing - special universal joint with axle . Why didn't LEGO make such universal joint...

Yes, it comes with several benefits, like independent driven front suspension with onli 15 stud width, better steering lock than cv joint offers. I know, Madoca1977 accomplished the same width by the floating diff in the Dacoma Pickup and I really admire that solution, but this special uni joint was a long time dream of mine. I was searching up and down Efferman's Shapeways shop, but I could not find it. (yet I remember the first time I met with the concept it was on his page) Anyway in a few days I got familiar with the ThinkerCad and made a couple of types of uni-joints I was missing from the Lego portfolio. The first generation I made (using shapeways printing service) turned out to be too fragile and had some size issue. Using the experience of the first generations faliure I've redesigned it and the next shippment fulfilled the requirements I made. Using it however comes with certain geometrical problems, as I built the wheelhubs. I've solved them by trimming some parts. ( I know...) But once I made dedicated wheelhubs for this uni joint, I could justify my savage actions.  I read in one of the other topics that people find the beauty of challange figuring out how to build without the "non existing parts". Respect for that, I'm a different type, I find the beauty in making those non existing parts. In return I have my own place reserved in Lego Hell. 

[tomek9210]

I love the custom joints too. If the price is affordable, I will definitely buy some. 

Awesome car and great performance!

[Attika]

1 hour ago, tomek9210 said:

I love the custom joints too. If the price is affordable, I will definitely buy some. 

Awesome car and great performance!

Thank you Tomek, I'm currently thinking how to make it available the design for public. I'd like to avoid to open shop on shapeways, so probably the best if I make simple 3d files for each part (or triplets speaking of uni joints) and just share as it is and everybody can choose the printing service by sympathy, or availibility. The current form of design contains far to much parts (72 joint end parts and 40 cross) for simple users :

In this form I've paid 55 dollars and about 11 dollars on postage. Crazy, isn't it? There was an experimental value for me, so worth it. 

[tomek9210]

Attika, thanks for answer! Some more questions from my side:

• How long is the axle on this joint?
• Is it sufficient for standard 56 x 43 rims?
• How do you rate the 3d printed parts after some use? Did they handle the torque well?

Whichever way you decide, either Shapeways shop or only file for printing it by your own, it would be great!

[Milan]

Very satisfying video to watch. Great performance!

Somehow I really miss a thin flex axle or something across that space where doors should be!

Same as Tomek, I would also like to hear how well custom joint works? I guess if thin gears in the diff withstand, then U-Joints are safe. So a better question may be: How strong they are compared to Lego U-Joints?

[Attika]

3 hours ago, tomek9210 said:

Attika, thanks for answer! Some more questions from my side:

• How long is the axle on this joint?
• Is it sufficient for standard 56 x 43 rims?
• How do you rate the 3d printed parts after some use? Did they handle the torque well?

Whichever way you decide, either Shapeways shop or only file for printing it by your own, it would be great!

 

3 hours ago, Milan said:

Same as Tomek, I would also like to hear how well custom joint works? I guess if thin gears in the diff withstand, then U-Joints are safe. So a better question may be: How strong they are compared to Lego U-Joints?

Sorry for the pause, I had to take my lunch  As you see on the picture I've posted there is a type with 2L axle, and another with 3L axle. This model uses the 2L type.

After extended use I can't see any visible wear on the ones used in the front wheel hub. This application being the first where i'm using these u-joints in motorised "enviroment", I have to say I'm happy with the results. No wear, and they managed to take quite a lot of stress, considering that in the front wheels there is many different kind of force trying to twist and brake them in every possible angle. Now the weakest point is of course around the socket of the cross, but my design is less resistant than Effermans heavy duty u-joints. Effermans design has more robust sidewalls around the thinner cross, I went different way, sidewalls are thinner and the cross is a bit thicker. As I had no opportunity to experiment a lot around prototypes, only had two printing all together, I wouldn't say I could optimise it. After I recieved the first printing, I realised the walls are thinner than on the 3d model I've made. According this experience on the next gen I've "overdesigned" the walls to compensate the "loss" on the physical printing. Also the 1st gen axle part was too thin so the wheels kept falling off. On the 2nd gen I've made them thicker. Even if it came out too tight for the lego axleholes, I could file them to the "right size". Yet somehow I remember reading about this problem in Efferman's topic. As I recall he doesn't offer crossaxle parts anymore due to the printig tolarence is too big for resulting perfect fit axle holes in Lego parts.

In other words even if you have the perfect size on the 3d model, the printed version might be loose or tight and it is up to the blind luck. My solution to design them thicker then carving or filing them to the right size. And this is the very reason I don't want to sell them on shapeways, but share the file made the best I can. Hope you understand my concern about it. 

Is it as strong as Lego's U-joint?

Well the quality isn't as "uniform" as in molded ABS. Some pieces in the same printing withstands more than the others. I had one piece breaking in my hands when I clicked the cross into it, others however:

It is pretty convincing, but I can't say it is true for all and every piece. Let say 85 percent is reliable.

The 1st gen printed white, and the 2nd gen printed red. Red is only a coatng on it so when it filed to the size the white material shows up:

The thing is: perfect combination for me was 2nd gen parts with 1st gen cross.

Hope it helped, if there is any questionm, hit me and I give my best. It would be great if @efferman would comment on this as the master of the subject. I am just trying my wings on this field.

 

3 hours ago, Milan said:

Very satisfying video to watch. Great performance!

Somehow I really miss a thin flex axle or something across that space where doors should be!

Thanks, and grats for the promotion "BOSS" 

About the doors: Either a proper door, or nothing. Uff.

Edited April 4, 2017 by Attika

[1gor]

17 hours ago, Attika said:

Yes, it comes with several benefits, like independent driven front suspension with onli 15 stud width, better steering lock than cv joint offers. I know, Madoca1977 accomplished the same width by the floating diff in the Dacoma Pickup and I really admire that solution, but this special uni joint was a long time dream of mine. I was searching up and down Efferman's Shapeways shop, but I could not find it. (yet I remember the first time I met with the concept it was on his page) Anyway in a few days I got familiar with the ThinkerCad and made a couple of types of uni-joints I was missing from the Lego portfolio. The first generation I made (using shapeways printing service) turned out to be too fragile and had some size issue. Using the experience of the first generations faliure I've redesigned it and the next shippment fulfilled the requirements I made. Using it however comes with certain geometrical problems, as I built the wheelhubs. I've solved them by trimming some parts. ( I know...) But once I made dedicated wheelhubs for this uni joint, I could justify my savage actions.  I read in one of the other topics that people find the beauty of challange figuring out how to build without the "non existing parts". Respect for that, I'm a different type, I find the beauty in making those non existing parts. In return I have my own place reserved in Lego Hell. 

and I can use them for Unimog axles that would be much more narrow - about 2 studs than current possible. I've used shapeways parts but they were to fragile, so I've become something like purist...

[efferman]

Very interresting crossaxle U-Joints. Have you any twist in the crossaxles?

[Attika]

6 hours ago, I_Igor said:

and I can use them for Unimog axles that would be much more narrow - about 2 studs than current possible. I've used shapeways parts but they were to fragile, so I've become something like purist...

 Please keep your hopes on a modest level about it's torque resistance, in this size with plastic no one can make miracles. As the angle is growing the torque resistance is falling. At maximum steering angle it might disappoint you. 

 

4 hours ago, efferman said:

Very interresting crossaxle U-Joints. Have you any twist in the crossaxles?

Interesting on a good way, or a bad way? 

Reading the question about the twist, first I thought you mean if there is twist caused by the forces in the usage, then I realised maybe you meant a twist by design to give tighter fit for the rims. Honestly till that moment I didn't even think about that, but it is a fabulous idea. The main reason I did not even think that way because I'm using it with Rc wheels, and the way I mount them is clicking a 12t half bevel gear in the hex hole. It does not contact on enough length with the crossaxle to let the twist effect apply on the connection. Another application would be spoiled as well: I made some free sliding counterparts for this u-joint crossaxles. (i guess I was stealing the idea from you) and the free slide attribute would be corrupted. Let me know if I missunderstood the question. By the way if you are interested I'd be happy to send the file for you. You obviously have more experience and equipment to "optimise" it and make it available for the community, as seemingly there is a demand on it.

[efferman]

Interesting in a good way, my attempt on this was to weak for a proper way. The twist  about iam calling is the torsion of the crossaxle under load. 

[Attika]

Just now, efferman said:

Interesting in a good way, my attempt on this was to weak for a proper way. The twist  about iam calling is the torsion of the crossaxle under load. 

I did not put "too much" torque on it yet, the most of the torture it went trough was the xl motor test (the video above), but it didn't do any permanent damage like twist on it. In the drift car it did not face too much torue due to the slipery wheels. What file type you would prefer to recieve? If you need it at all I'm not an expert on this whole thing so help me which extesion should I download or dig up?

[efferman]

Stp should work to open it.

[Attika]

2 minutes ago, efferman said:

Stp should work to open it.

Please don't laugh on me, I made the design on thinkercad, and the options I have: STL, OBJ, X3D and VRML. This is the point I feel my age. 

[efferman]

Ok, these filetypes my inventor cant open.

[Attika]

Just now, efferman said:

Ok, these filetypes my inventor cant open.

Cool, I send it in a private message as we are kinda off topic in this depth and @Milan is going to kick my butt on his first day as moderator.