Crazy axles idea design
 

Hi, I am new to the forum but not to the hobby. I have been designing, constructing and piloting RC cars, planes and helicopters. I designed my first RC car when I was 13 years old and that was 35 years ago...

I lately come interested on Rock-Crawlers, mainly on the superclass, because I think it is the more technically advanced.
After some research I come to some conclusions about Crawlers that I hope they are correct, you let me know:
- Manny of characteristics of a Rock-Crawler are very different than from a speed-racing car.
- Vehicle weight should be as low as possible.
- CG should be as low and forward as posible. In order to achieve that weights are installed on the front wheels.
- As much suspended mass the better.
- As much turning radius the better.
- Brushless motors are not well suited for the task unless they are sensored (difficult to find)

So in order to meet those parameters I come up with this design/idea of how to install all equipment (weight) inside of the wheel rim. It is just a quick render and before going further with it i will like that you have a look to it and give your opinion/suggestions and if I you think it can work.
If I go forward with this I will need some assistance on setups and other details and hope you can help me.
Let me know if you can see the pictures, if not I will link them differently.

https://scontent-mad1-1.xx.fbcdn.net...4d&oe=5AE779B3

https://scontent-mad1-1.xx.fbcdn.net...98&oe=5AF7CDE5

Equipment planing to use:
4 x 380/385 brushed motors
4 x 20-25A ESCs
2 x 7.4V (2S) 800-850mAh batteries (one on each front wheel)
4 x 15-20Kg Standard size servo

Re: Crazy axles idea design
 

Sound like motor on wheel system ?

Re: Crazy axles idea design
 

Here ya go.. a little inspiration!

Bc-brian of Lattice Innovation (a vendor here, that makes the Sickest hubs on the market, Shift hubs) designed this little beauty..

http://www.rccrawler.com/forum/unlim...ing-crazy.html

Re: Crazy axles idea design
 

Yes, that is right Teng MOW system.

Thank you Bc-brian, I seen your rig, it is great, it was quite inspirational for this idea. Actually after seeing/reading you post I decided to go brushed way instead of brushless.

Re: Crazy axles idea design
 

Calculating the steering geometry, actually not an easy task. Thanks that Ackerman Geometry is not needed :ror:

https://scontent-mad1-1.xx.fbcdn.net...bb&oe=5AE5BF0B

About 70º, not bad I think.

https://scontent-mad1-1.xx.fbcdn.net...1d&oe=5AE38243

Re: Crazy axles idea design
 

Gear box taking shape. I will 3Dprint it.
Now needs servo, and battery support, Kingpin hears and some more details.


https://scontent-mad1-1.xx.fbcdn.net...b0&oe=5AF1E9F3

Re: Crazy axles idea design
 

What size wheel are you using to be able to fit a 380 motor and gear box inside like that?

Re: Crazy axles idea design
 

Wheel rim diameter is 152.8mm (around 6") and tire diameter 205mm (around 8")
Moreless the same wheels sizes as other Superclass that are around.

Re: Crazy axles idea design
 

First iteration of the gearbox finished, lets see if I can print it latter today, in order to see if everything fits and check tolerances...

Inner side (Servo, motor, battery)

https://scontent-mad1-1.xx.fbcdn.net...94&oe=5AF25DEA


Outer side (Space for the ESC and weight box)

https://scontent-mad1-1.xx.fbcdn.net...63&oe=5AECD127

Re: Crazy axles idea design
 

Its already been done. You might want to do some reaearch.

Re: Crazy axles idea design
 

Everything has been done but there is always room for someone else to try something similar.

Re: Crazy axles idea design
 

Keep up the good work, always to see cool stuff that continues to innovative.

Re: Crazy axles idea design
 

Say that again when this dude hands you you're hiney on a platter at worlds and says.... Would you like some tapas and sangria to compliment your ass. :mrgreen:


Good work.

Re: Crazy axles idea design
 

I can’t wait to see how this pans out.

Looks like it will be a great build.

Re: Crazy axles idea design
 

This looks so sweet!!
What kind of gear reduction you getting out of that worm drive, somewhere around 30:1?
Cant wait to see how this turns out.

Re: Crazy axles idea design
 

Hey f@#$heads did i tell the guy not to do it or offer an opinion?

No i told him its been done and to do research. There is literally no reason to reinvent the wheel when you can go do research on how it is done.

Re: Crazy axles idea design
 

Or you can see what’s been done, find the flaws and improve on it.

Re: Crazy axles idea design
 

Yeah exactly why you should do your research.

Try not to inject your bias when you read. A statement is a statement and nowwhere in mine does it offer an opinion. You people want it to be negative so you can have something to post about.

Re: Crazy axles idea design
 

Just looking at the models posted it is pretty obvious the research has been done. :lol:

Re: Crazy axles idea design
 

Thank you all for your kind words.

Yeah, I have done quite of research in order to end up with this.
Actually a very helpful one was this thread from BC-Brian here: http://www.rccrawler.com/forum/unlim...ing-crazy.html

I was first thinking on using brushless motors as there is a huge offer and their higher power density, but that thread made me change mind and go brushed way, because I realized that a brushless motor without sensors will not give enough torque at 0-low rpms.
Even with a sensor motor it will be a bit complicated due to the great amount of cables (7 from each motor)

Yes that is right 30:1 (https://shop.framo-morat.com/en/Worm...r-distance-25/)
Planning to use this motors reference RS-380PH-4045 from Mabuchi, if I can find them: https://www.mpja.com/download/17946md.pdf
If not there is similar KV 385 motors from other brands that may be even better suited than the 380.
It will be a test error thing…

I did not had time to print the gear box test, it will have to wait till the weekend probably.
Anyway I had time to work on the axles design. Still do not know where to place the shock absorbers, do you think that the lower links rods is a good place?. Note that the rods will be straight, they do not need to be bended as they are on a very high position.

Axles taking shape:

https://scontent-mad1-1.xx.fbcdn.net...44&oe=5AE79115

Re: Crazy axles idea design
 

I managed to print one of the gear boxes, now is time to check tolerances, interferences, etc. quite long and tedious process.
As well I started to design the chassis.

The 3D prime of the gear box, it is a quick print so quality is not great.
https://scontent-mad1-1.xx.fbcdn.net...da&oe=5ADB3148

https://scontent-mad1-1.xx.fbcdn.net...4d&oe=5B20AABB

Re: Crazy axles idea design
 

This is bad-ass! If you run into strength problems with your prints you can look into having someone print your parts in Markforged onyx. Also, have you thought about using a small brushless outrunner on a gear-head? That might be a good path to research if you run into gearing problems.

Re: Crazy axles idea design
 

Thank you Highmark,
It is beefy designed and I was planing to test Nylon, PC and PETG to see which one is the better suited for the task and my printer. Last option will be if someone can print it on a Markforged one as you say.

The first idea was to use brushless motors but I was not able to find small sensored ones.
And because efficiency is not an issue in this case, and more weight where they are located is not a problem as well, I decided go brushed way...

Re: Crazy axles idea design
 

All linkages are set up now.
I do not know how to proceed with the chassis. Going the standard way with plates and cross-members or doing something more creative. :roll:

https://scontent-mad1-1.xx.fbcdn.net...6e&oe=5AED2D58


The steering that is posible with this setup is almost ridiculou , 70º on both axles.:mrgreen:

https://scontent-mad1-1.xx.fbcdn.net...6b&oe=5AEB1CC4

Re: Crazy axles idea design
 

70* is pretty standard these days. Make the axle "tubes" smaller and go for 80* and really prove something. :mrgreen:

Re: Crazy axles idea design
 

I though that the actual range was about 50º-60º most. :shock:
Actually it can goes a bit more than 70º, around 72-73º and yes certainly it will be able to go even more with more scrub and reducing the axles sizes, but I do not know if I want to start redesign so much, it means lots of work :cry:

I will let that for next version update.

Re: Crazy axles idea design
 

While 70degrees is a standard these days. This won’t have the speed up and slow down that you tend to get with the current products available.

The other main issue is that when your running that much steering you get really bad pushing forward. The only way to stop it, would be to work out some fancy radio mixing to overdrive the outside wheel at full lock.

To the original poster. Keep up the great work.

Looks like your going to need at least a quad stick radio. Might as well have is so you can mix the steering so both front wheels can go opposite each other.

Re: Crazy axles idea design
 

Yes, plan to use stick radio, with one axle steering and gas on each stick.
Similar to helicopter flying :badger:
Then both steering axles can be controlled differently and even the throttle of each axle can be controlled separately so each axle can go on reverse direction than the other. Do not know what weird effects this will cause :lmao:

Re: Crazy axles idea design
 

Finally decided to go on a fancy chassis design. :mrgreen:
It is the first version with lot of holes in order to test different configurations.
Depending what holes are used on the chassis and other changes on the wheel shafts, different setups can be achieved:
- 0º to 30º Caster angle.
- 15mm to 25mm positive Scrub radius
- Multiple Antisquat Antidive positions for the links arms
- +-30mm wheel base adjustment
- 0 Akerman (Can not adjust)
- 0º Camber angle (Can not adjust)
When geometry defined I will modify that chassis to make it lighter and simpler.

I know that every one uses different geometries, but if you do not mind to share the ones you are using on your rigs, it will give me at least some ideas where to start.

https://scontent-mad1-1.xx.fbcdn.net...55&oe=5B1E31B3

Re: Crazy axles idea design
 

And here is the final full assembly. I did not draw the shock absorbers, as I do not think it is need, they are represented by the red links.
As well I did not added the screws, nuts washers, as it is just a hobby design.
Now it is time to start ordering parts.
First I will order gears bearings and motor to check if gear box works ok.

https://scontent-mad1-1.xx.fbcdn.net...32&oe=5B15DE33

Re: Crazy axles idea design
 

Awesome idea!
I think It needs a pimp-cane chassis[emoji23]
That would really flip people out.
Do you foresee the instant-brake of a worm drive to be an issue? It’s like having 100% drag brake

Re: Crazy axles idea design
 

Thank you for the input Tzi
Although I like the simplicity of a pimp-cane chassis, I think it does not work very well. Because it does not flex on its length.
Anyway you made me think that I could go more radical on the chassis.
So I have spent some hours doing maths and geometry... will post about my hypothesis soon.

Yes it will probably be an issue, and will require special TX mixings and an especial driving license :lmao:

Re: Crazy axles idea design
 

I don't think that's enough adjustable mounting positions... :lmao::lmao: Looks great, cant wait to see how the gearbox works.

Would you ever consider making the files for some/any of these parts available for others to use?

Re: Crazy axles idea design
 

;-) yes you are right, I have reduced the number of holes on the final version, after checking all adjustments and clearances.
Will post final version latter.


I will print and check functionality first, modify if necessary (for sure...) and then will post files and designs on thingiverse or somewhere else.

Re: Crazy axles idea design
 

That would be awesome! You have put in a lot of work on the CAD for this project, I hope everything goes together IRL as well as the CAD model.

Re: Crazy axles idea design
 

I thought that I already had posted this, but apparently went missing on the internet ocean... :shock:

I have checked tolerances, interferences and other issues so here is the final version V1 that I have named Gosainthan, it is a quite standard chassis that can be 3D printed. I reduced the number of holes to just the most usable ones but still a lot to play with. Now it looks more slick and cool and it is lighter. As well I added holes on the top axle link mount so there is more possibilities for adjust the caster angle.
It can use one way or two way shock absorbers from 80 to 110mm.

Provably after printing and testing will need some redesign and adjustments. :roll:

https://scontent-mad1-1.xx.fbcdn.net...b5&oe=5B1F3FDB


Later I will post V2 Gasherbrum version.

Re: Crazy axles idea design
 

As Tzi sugested on a previous post, I went a bit wild on chasis design and decided to design something more radical, well actually it is almost no chassis at all. So this is the V2 version, named Gasherbrum
It share the same axles as the

As it is just some small 3D printed parts and some links will try it and if it does not work I can always go back to Gosainthan version.

Let me know your thoughts.

https://scontent-mad1-1.xx.fbcdn.net...f6&oe=5B0DEC40

Re: Crazy axles idea design
 

One thing I would look at is your upper link mounts.
I’d consider adding some more holes on the other side of the current mounting bolt.

I know for the front it’s not required as the caster will go the wrong way, however on the rear you would be able to position the caster angle closer to the same as the front axle.

I used to run zero degree caster in the rear, but has been playing around with caster on the rear and found it can be handy for a little bit more traction on the edge of the Tyre.

Re: Crazy axles idea design
 

If my brain is seeing that very cool second chassis right, you would need some very stiff springs in order to keep it from being super floppy. The links sharing the same mounting holes on the chassis means that blue "chassis" can just rotate forward an backward (on an axis similar to the wheels spinning, if driving straight), taking the axle with it. This will make the caster change as the load on the axles change.

I could be wrong, but figured I would let you know.

Re: Crazy axles idea design
 

It is already thought, the red part that looks like an spur can be mounted on both directions so you can have positive or negative camber (0º to +-25º) on both axles. "thumbsup"