[WIP] Greyhound - 4WD RC Buggy with BuWizz 2 - Redesigned wheel hubs

[Lox Lego]

2 hours ago, Didumos69 said:

Thanks! The whole front module is mounted to two lengthwise beams. The difficult part was to firmly connect those beams to the main structure and to introduce a caster angle at the same time.

I continued working on the main structure. I now also have most of the width-wise structure done and integrated two removable BuWizzes. Also the trailing arms of the rear suspension are completely integrated now. Only need to add a connection between the topside of the front module and the sides of the main structure and then the chassis design should be done.

 

Wow.... this thing looks mean... and you haven't even started the bodywork!! Wild looking frame, very excited to see this one complete!!!!!

[Didumos69]

On 12/15/2017 at 2:19 PM, DugaldIC said:

This thing is looking more rugged than your supercar. I can't wait to see some footage of it ripping around it'll fly with four L motors and two buwizz. 

On 12/15/2017 at 4:36 PM, Lox Lego said:

Wow.... this thing looks mean... and you haven't even started the bodywork!! Wild looking frame, very excited to see this one complete!!!!!

Thanks brothers! So far it has half the number of parts of the chassis only version of my rugged supercar. There is quite a lot of empty space packed in this one.

I added a connection between the top of the front module and the sides of the mid section. I used 9L steering rods. That should give the front module width-wise stability. Next step will be to mount the shocks for the rear suspension and then it's time to buy some motors .

 

[schraubedrin]

19 hours ago, Didumos69 said:

This is so awesome. How do you keep on finding those perfect connections?

[Didumos69]

13 hours ago, schraubedrin said:

This is so awesome. How do you keep on finding those perfect connections?

Thanks! I'm constantly looking for Pythagorean triples and quadruples. 9L track rods span a heart-to-heart distance of 8L. In this case they are in-grid with the front module and it can be easily observed they span 6L length-wise, 5L width-wise and 2L height-wise. That makes a heart-to-heart length of sqrt(6^2 + 5^2 + 2^2)L = sqrt(65)L ≈ 8.06L. No perfect fit, but when using track rods, there is just enough slack in the tow-ball connections to make this a tight fit.

[Erik Leppen]

Also, the towball pins they connect to, aren't parallel, so the 8.06 isn't the exact distance. My guess is that it's about 0.06 less, due to the fact that the pins on the front suspension unit are slanted slightly, yet the pins on the chassis are vertical.

[agrof]

Looks nice, I am curious about real life stability.

I admire the commitment to work 100% in system, but for me 0,06 stud distance is largely in tolerance. I would say it would matter only, if the real parts would be 100% rigid (which is bad, than they would break more easy - assumed to be made of affordable plastic material), and wouldn't have calculated tolerances. Maybe 0,1-0,2 does make a difference, but below that I would just gently pass by. 

I don't want to be a party smasher, it is just my opinion - I like to use the material properties (like elastic modulus), and following with great interest the mathematical aspect of building. 

EDIT: @Didumos69 I would like to ask, if You check in IRL build what parts can be removed without loosing structural rigidity? Sometimes it is easy to overengineer some solutions, without real added value, in return we get increased weight. In this build the weight is really critical, as it has significant influence on overall performance - for a manual model it is not an issue. To maximalize the effectiveness of the 4 L motors, I would double check everything to cut off the weight as much just possible. I had this experience that time with my Class 1, I would say, to revise and to find all unnecessary parts took almost the same time as building up the model first.

Edited December 18, 2017 by agrof

[Didumos69]

3 hours ago, Erik Leppen said:

Also, the towball pins they connect to, aren't parallel, so the 8.06 isn't the exact distance. My guess is that it's about 0.06 less, due to the fact that the pins on the front suspension unit are slanted slightly, yet the pins on the chassis are vertical.

You are right, I did not take the inclination into account yet. Given that the inclination is 5 degrees, the exact heart-to-heart distance is:

sqrt((6 - sin(5 / 180))^2 + 5^2 + (2 + (1 - cos(5 / 180)))^2) ≈ 8.04

2 hours ago, agrof said:

but for me 0,06 stud distance is largely in tolerance

I agree that LEGO has quite some tolerance, especially when you take the tolerance of connections into account. I wouldn't want to claim that working 'in-system' is 'better' than going by 'whatever fits'. It is to a certain extent a purely personal thing. However, I am convinced that working 'in-system' paves the road for a gradual design without running into 'won't fit'-problems and allows for more easy adjustments down the road. This way of working also makes it more easy to see opportunities where you can replace several parts with a single part. For instance, when I see the opportunity to replace some parts wit a T-bone piece or a 5x7 frame and it adds to cohesion, I won't hesitate to make that change.

2 hours ago, agrof said:

I would like to ask, if You check in IRL build what parts can be removed without loosing structural rigidity?

Thanks for pointing this out @agrof. I am aware that in this kind of builds it is even more important to limit weight. I have built the front module and already skipped quite some parts and will keep on trying to remove parts during the rest of the real life build process. Even more now that you have emphasized this.

Btw, here is the LXF of the front module. Please let me know if you see anything obvious to skip.

Edited December 18, 2017 by Didumos69

[agrof]

Sure, it is a personal taste, no question about it, and this is the beauty of building LEGO. 

So, here are my quick thoughts: click for LXF. I would get rid of half beams / levers where possible, for sake of rigidity, I would use homogen parts rather. Too many parts = too many connections = too many small flex, inaccuracy in the system, which might cause saggy assemblies. You know this better than me, most probably. 

I see the point why You used half beams for the swingarm, but I think this version is also worth to test. I removed some parts, I would test so first, and see how the swingarm behaves. Also there is an alternative for the steering link - I don't know which is better, and I haven't calculated  - I just rely on LDD here, it fits. Must be tested which connection method is more rigid.

For the frame I can not add much at the time, as I don't know, which connection points are needed for the rest of the chassis / body.

Sorry, I destroyed the beautiful group structure as I worked with more copies in the scene, lime parts are my suggestions (on the right side), magenta ones which I think can be removed (on the left side). I hope this gives constructive value to the project.

Edit: I am in flow a bit, I made a 2nd version - just these parts added/replaced, due to stability at the springs hinge area, and to form brake caliper-like shape:

Just checked the connection with this steering link - towball solution, there is some misplacement indeed, so does not fit to your philosophy. (For me it would, as Mr LDD - the great censor - allows it, and I am pretty sure it would work IRL too.)

I am wondering, if the steering rack could be replaced with 7M version, I really like the tricks in the current version, just curious if it could work.

 

Edited December 18, 2017 by agrof

[Didumos69]

1 hour ago, agrof said:

So, here are my quick thoughts: click for LXF. I would get rid of half beams / levers where possible, for sake of rigidity, I would use homogen parts rather. Too many parts = too many connections = too many small flex, inaccuracy in the system, which might cause saggy assemblies.

Thank yo very much @agrof!

I like the idea of using the 7L liftarms instead of thin ones. I will certainly try that.

1 hour ago, agrof said:

Also there is an alternative for the steering link - I don't know which is better, and I haven't calculated  - I just rely on LDD here, it fits.

I tried something like your steering links earlier. It introduces toe-in even though LDD sais it fits, and it does not give Ackermann geometry. But there is an other problem. The 5L suspension arms that connect to the wheel hubs collide with the wheel hub when the steering angle is max and the suspension is max compressed  or max expanded.

You seem to have messed up the lime green wheel hub a bit. It misses the half bushes to create space for the wheel hubs to rotate around the suspension arms. Therefore 4L axles with stop you used are not an option, I need at least 4.5L.

The blue parts at the bottom A-arm are nice, but they collide with the motor when the suspension is compressed.

Thanks for thinking with me! I will let you know how this will effect the design.

[agrof]

Hmmm, I admit the steering link caused issue.

Just now, Didumos69 said:

You seem to have messed up the lime green wheel hub a bit. It misses the half bushes to create space for the wheel hubs to rotate around the suspension arms. Therefore 4L axles with stop you used are not an option, I need at least 4.5L.

The blue parts at the bottom A-arm are nice, but they collide with the motor when the suspension is compressed.

The first part: I see now, correct, sorry for that.

The second part: do You mean this part: ? I don't dig it, everything moves parallel in the A-arm, so the space inbetween should always be the same...

[Didumos69]

1 hour ago, agrof said:

You mean this part: ?

Yes.

1 hour ago, agrof said:

I don't dig it, everything moves parallel in the A-arm, so the space inbetween should always be the same...

The bottom side of the motor rotates outward when the suspension compresses. Try to place the blue part in the same position of the upper A-arm.

I just implemented the A-arms with 7L liftarms. It is indeed more rigid ! And much more simple. Thanks!

[agrof]

Ok, your turn. 

[Didumos69]

1 hour ago, agrof said:

Ok, your turn. 

Haha, my mistake. Nice solution ! I will use it.

Edited December 18, 2017 by Didumos69

[sawyer klegr]

Your a genius! Whenever I use Lego's version the U joints they just disconnect, but you versions should be able to handle some torque. Thank you for this :-) 

My YouTube Channel

Edited December 19, 2017 by sawyer klegr

[Didumos69]

Back into cars. I received all motors and springs and ordered two BuWizzes. The motors fit very well in the front suspension. I also incorporated several of @agrof suggestions.

Edited February 1, 2018 by Didumos69

[Lakop]

I like what you are building but what brand are those storage boxes in the background? I'm out growing my current boxes.

H

[Didumos69]

40 minutes ago, Horace T said:

I like what you are building but what brand are those storage boxes in the background? I'm out growing my current boxes.

H

Those are Raaco assortment boxes. They came with removable inserts of various sizes. I used the inserts before and even the smallest parts would stay right in where I put them. Eventually I removed the inserts, because the boxes could store much more without them. I bought these boxes at a local hardware store.

[Leonardo da Bricki]

Saw your post and photos above, and suddenly had much jealousy... That axle looks great, I cannot wait to see the performance of this racer, it ought to be insane!

[Didumos69]

On 1/31/2018 at 11:05 PM, Leonardo da Bricki said:

Saw your post and photos above, and suddenly had much jealousy... That axle looks great, I cannot wait to see the performance of this racer, it ought to be insane!

Thanks! I hope it will perform well.

I finished designing the entire chassis. Also properly mounted the rear springs. 947 parts sofar, which is quite neat for a complete chassis at this scale, I think.

Edited February 2, 2018 by Didumos69

[TheNextLegoDesinger]

looks great, i guess those grey studded block are supposed to be AAA battery boxes?

[Aventador2004]

27 minutes ago, TheNextLegoDesinger said:

looks great, i guess those grey studded block are supposed to be AAA battery boxes?

No, buwizz boxes.

On 1/31/2018 at 3:22 PM, Didumos69 said:

Back into cars. I received all motors and springs and ordered two BuWizzes. The motors fit very well in the front suspension. I also incorporated several of @agrofsuggestions. 

This should explain.

[Didumos69]

Edited February 2, 2018 by Didumos69

[letsbuild]

Do you have room around the Buwizz to plug in your motors? It looks like there's not enough...

[Didumos69]

41 minutes ago, letsbuild said:

Do you have room around the Buwizz to plug in your motors? It looks like there's not enough...

That's a good question. Going by this image (courtesy of @kbalage) I reckoned there would be enough space to have the cables bend over the 5x7 frames, but now that I look again you might be right.

If someone knows this is not enough space, then please let me know.

Edited February 2, 2018 by Didumos69

[letsbuild]

1 hour ago, Didumos69 said:

That's a good question. Going by this image (courtesy of @kbalage) I reckoned there would be enough space to have the cables bend over the 5x7 frames, but now that I look again you might be right.

:snip:

If someone knows this is not enough space, then please let me know.

Yes, that's right. I didn't realize the outputs were so far in. It is quite possible that it will work.