Krazed Builds Capra 2.2S Pneuma

[Robbob]

So the cats out of the bag on our latest Capra axle based 2.2S build. After seeing how well the Alcista handled with Capra axles we decided it was time to sit down and really design a comp version of our next Shafty chassis kit to come.

We took everything from our notes on our 2018 Nationals Portal rig and did some deeper digging into geometry and our math. Again I will say Axial nailed it with these axles. I loved the portal rig I built prior to this and learned so much from it and from talks with some great OG comp guys. The few things I battled with that rig I started educating myself more on. Understanding geometry and the real engineering side of our little trucks and the evolution of crawling .

My main goal was to design a new chassis able to win with our conventional older axles while benefiting from the newest type being portals. First I must say the myth of portals raising your COG I believe to be just that, a myth. Let me explain my thinking.

Lets take our past shafties and sit the truck on our bench. Now Im gonna use measurements loosely but lets say we have a belly that sits 3'' off the ground. Our axle centers are 2.5'' off our bench with tires on. Now most people would say well you raised everything up because you raised the axles so your COG rose.

Wrong ..... Now lets say you lowered your belly a half inch on the same truck. Did you raise or lower your COG? Most would agree you lowered it because you brought the chassis/trans closer to the axle center right? Now lets say you kept your belly at 3'' and raised only your axle center (not the wheel center) a half inch. So yes you brought axle weight up but now look at all that room you have 'below' the axle center to add weight.

Before you only had 'loosely' a half inch of room to add weight below the axle center. Now you have a wheel center thats a half inch lower then your axle center. Virtually doubling the distance now with portals that you can get weight below the 'axle' center. I will say I define 'axle center' as your axle/ring n pinion gear and Not the stub axle your wheel rides on. When you add in the portal gears you have more weight to begin with below the axle.

So in my theory Im able to stack upwards of 157g per side with loaded dice wheels, upwards of a crazy 255g per side with rock magnet hangers. All that weight is farther from the axle center then able to be before. This lowers my COG since I didnt move the chassis up, I only moved the axle housing and corrected some geometry restrictions we had before.

Crazy? Ya im no 'engineer' that can mathematically explain it but just let that ponder.

Now with that theory and my experience from the last rig I knew I had my notes right. Measuring everything out and running ideas for my goal in this chassis I came up with this which became 3 prototypes.






Believing in 3D printing and have been doing it for a couple years now all our skids come printed in PETG.


For my own personal I went to try some real carbon fiber PETG material for printing. Strong and a bit lighter.


For my own rig I went with my own transmission and 23% internal overdrive for the front axle. I will say I wont be producing these though, theres just too much work and theres plenty of reliable options already out.

Ive been testing with my own truck for quite a bit lately and must say it feels good driving a shafty again. Especially this one that is just above anything Ive driven over the years. But after some talks with another team driver and some talks with a some OG drivers I made a couple geometry changes and so far loving the effects of them. And here I am now with our newest prototype for some more testing.




I also went to the front axle with a strong servo and electronics plate that cleared the upper links and not printed.



So there it is ..... We are calling our 3rd generation shafty chassis 'Pneuma' meaning the vital spirit, soul, or creative force of a person. Now we arent looking to replace the Alcista or believe any less in it because of the Pneuma. The Alcista really is a way to wake up a Capra for drivers looking to try the competition side of crawling. We believe in the hobby and ways to attract new blood with out breaking the bank. The Pneuma is our dedication to the drivers looking for that upper edge over the older, past thinking of shafty rigs. More testing and practice this friday and hopefully some good video for it.

Thanks for looking .......

[Robbob]

Heres some basic setup info Im running with right now.

Servo: Hitec 7950
ESC: Holmes BR Mini
Motor: Holmes Puller 500
Battery: 3S 500mah
Tires: Rover white rear - Rover Pink front all shaved and softened up
Foams: Crawler Innovations 5.25 Med rears/Soft fronts

Shock Oil:
Front: 37.5
Rear: 42.5

Springs:
Front: Element Greens
Rear: Element White

Truck RTR Weight: 4.13lbs

Hot Bodies Front OD AR44 gear
Trans OD: 23%

Front knuckle weight: 74grams per side (rock magnet hanger + 1 tungsten slug)

Body: Jconcepts Illusion Mini E-revo body (have bubble roof to help with roll overs)

[marcosdo99]

I am glad to see that with the output of the new axial capra there are still new possibilities for competition crawlers. This particular chassis just look amazing joining the carbon fiber and the 3d parts on that way, I hope to have one and update my old comp crawlers. a magnificent job

[JatoTheRipper]

I'm not a comp guy, but the carbon fiber and neon green combo is sweet. The chassis looks awesome!

Your printed parts also look great. PETG FTW. It's my favorite as well. What printer are you using?

[TheLetterJ]

Tool fan? First thing I thought of:

https://youtu.be/5ClCaPmAA7s

What sort of geometry changes (with out giving up your secret formula) does this have over, say, your Alcista? Is the skid included? If so, what trans is it set up for? I know it's not ideal, but could one use their stock Capra links (does the Capra skid also fit this chassis?), bolt it together and go?

What's the weight of your Pneuma chassis compared to a Capra cage?

I'm already reevaluating my Capra. With only a set of brass knuckles and portal covers, it's already broken the 6lbs mark with a battery. I was hoping to be at/under 5lbs and I can see it's going to take more than a set of ti links to get there so a significantly lighter chassis has me intrigued.

[Robbob]

Originally Posted by marcosdo99

I am glad to see that with the output of the new axial capra there are still new possibilities for competition crawlers. This particular chassis just look amazing joining the carbon fiber and the 3d parts on that way, I hope to have one and update my old comp crawlers. a magnificent job

Thank you!

Originally Posted by JatoTheRipper

I'm not a comp guy, but the carbon fiber and neon green combo is sweet. The chassis looks awesome!

Your printed parts also look great. PETG FTW. It's my favorite as well. What printer are you using?

Ive had my Anet A8 for almost 4 years now and have a lot of mods to it. Bigger power supply, bed and hot end mosfet mod, frame braces, inductive bed leveling, glass bed printing on blue tape. I can drop anything on it and the thing just prints flawless for me.

I also have an Ender3 with a bunch of similar mods to it, Bigger power supply, hot end mosfet, micro swiss hot end, updated and tweaked Marlin, updated better control board, BLTouch leveling (i love it!), Ender3 print surface. Ive only had this one for about 2 years and its so dialed I just watch the leveling and first layer then walk away.

Im still using Cura on their latest 4.4v build. Ive learned a lot over the last few years about designing limits with prints. Building in tolerances for material squish and expansion has really been the biggest thing to learn. Cura's new profiles are so much better then their generic ones in versions 3.0 and older. I can sun a 1.5 layer height using a .4mm nozzle and not worry about anything now.

Originally Posted by TheLetterJ

Tool fan? First thing I thought of:

https://youtu.be/5ClCaPmAA7s

What sort of geometry changes (with out giving up your secret formula) does this have over, say, your Alcista? Is the skid included? If so, what trans is it set up for? I know it's not ideal, but could one use their stock Capra links (does the Capra skid also fit this chassis?), bolt it together and go?

What's the weight of your Pneuma chassis compared to a Capra cage?

I'm already reevaluating my Capra. With only a set of brass knuckles and portal covers, it's already broken the 6lbs mark with a battery. I was hoping to be at/under 5lbs and I can see it's going to take more than a set of ti links to get there so a significantly lighter chassis has me intrigued.

LOL Love Tool although I do love the newest album, except for chocolate chip trip, I dont think its any better then their others and we waited too damn long for it.

Pneuma is my favorite off the album and Im always curious to what Tools songs are about. Trying to think of a name for this chassis I remembered the definition and knew Pneuma was perfect for it.

The lower triangulation is the same, actually you can use stock Capra lowers. I added in a bit of triangulation adjustment though front and rear. Not a lot but enough that when I tried it in the rear I noticed the rig tightened up on me and drove significantly different.

Uppers were a bit more with math finding a good length front and rear and also noticeable changes to anti-squat and dive characteristics. Weight transfer I believe is smoother but still aggressive not letting either axle over power the opposite.

And last was shock angles in correlation to lower link and axle travel. Ive always ran my shocks at certain angles and never liked that laydown look many use. I believe in the shock doing work and laying them down just seems to make them cam out to early meaning they really arent doing anything. The Alcista actually uses the same angles giving the rig a better balance corner to corner. Consistency through the shock travel instead of running thicker oils to slow them down.

My daughters Alcista conversion weighs in at 4.63lbs RTR with Rock Magnet hangers on the front. Shes got about 120g of weight per side on hers, more then I targeted for my Pneuma but I wanted hers heavier to help with her learning to drive.

My Pneuma weighs in at 4.06lbs and thats with 4mm side plates and 85g per side of axle weight. I tried less weight up front and came in at 3.75 but it honestly was too light. My driving has always liked a rig around the 4.20* mark, even my pro rig comes in at 4.15 and loves it. Im happy with it where it is, lets me go lighter if tuning allows it or go heavier if traction needs it.

[OSRC]

I don't know much about comp rigs, but that is absolutely bad ass. That green/carbon combo is fantastic!

[Robbob]

The skids will come blank so you can drill them for any trans you want. No the stock Capra skid wont work. Our kit will come in standard black PETG but our Shapeways store will have options for colors.

The printed body mounts will be Shapeways. They make mounting a body easier but structurally not needed so you could fab your own mounts if desired.

The printed edging will be an add on option from us and done by us. The front axle plate will be 4mm carbon fiber machined to clear the upper links and supplied with servo mounts to off set the servo. It will fit your electronics and Id say any 3S lipo in the 600mah or smaller battery.

The chassis sides will come standard 2.5mm carbon fiber but we will offer a 4mm side plate option. Surprisingly the 4mm is not much heavier then the 2.5mm, it just adds some extra stiffness for those wanting it. We thought about the typical 2mm like we've always used. Its really not that big of a weight savings and would have some flex we dont think would be beneficial so we decided not to.

[Robbob]

Ohh almost forgot some weight pictures for comparison. Although I dont use the scales much for crawlers its always neat to see how close to balanced they are.

This is my Daughters Alcista conversion
60% front bias and 50/50 corner to corner


My Pneuma
65% front bias and 50/50 corner to corner


My 5th Dimension Dominator Pro (which looks like it needs a diet lol )
65% front bias and 50/50 corner to corner


Just food for thought when rigs hit the scales

[JENS]

Very nice !!

When can I buy it ?



;

[Panther6834]

Sleigh your daughter's Alcista haa different weights, it's "interesting" that the front-to-rear, as well as the left-to-right, percentages are identical to my Imperial Goat...60/40 front/rear, & 50/50 left/right. For the 2nd Capra I'm building, CAPbRAstard, I'm hoping to get 65/35 & 50/50. I'm temporarily "shelving" my Alcista project (ie. 3rd Capra) to focus on CAPbRAstard, as I'm hoping I'll have it completed before Nationals in LV.

~ More peace, love, laughter & kindness would make the world a MUCH better place

[Almighty Malach]

I hope the body mounts on this one are easier to figure out.

[JatoTheRipper]

Originally Posted by Robbob

Ive had my Anet A8 for almost 4 years now and have a lot of mods to it. Bigger power supply, bed and hot end mosfet mod, frame braces, inductive bed leveling, glass bed printing on blue tape. I can drop anything on it and the thing just prints flawless for me.

I also have an Ender3 with a bunch of similar mods to it, Bigger power supply, hot end mosfet, micro swiss hot end, updated and tweaked Marlin, updated better control board, BLTouch leveling (i love it!), Ender3 print surface. Ive only had this one for about 2 years and its so dialed I just watch the leveling and first layer then walk away.

Im still using Cura on their latest 4.4v build. Ive learned a lot over the last few years about designing limits with prints. Building in tolerances for material squish and expansion has really been the biggest thing to learn. Cura's new profiles are so much better then their generic ones in versions 3.0 and older. I can sun a 1.5 layer height using a .4mm nozzle and not worry about anything now.

Looks like you have those printers dialed!

I used Cura with my Monoprice Select Mini, but with my Prusa i3 you get PrusaSlicer which is a customized version of Slic3r. That's been excellent. Not that I had any complaints with Cura.

[CM9000]

y'know... i think my ventru build needs a brother.

Sent from my LGMP260 using Tapatalk

[KulaHI]

Originally Posted by Robbob

I also have an Ender3 with a bunch of similar mods to it, Bigger power supply, hot end mosfet, micro swiss hot end, updated and tweaked Marlin, updated better control board, BLTouch leveling (i love it!), Ender3 print surface. Ive only had this one for about 2 years and its so dialed I just watch the leveling and first layer then walk away.

I’ve got the Ender 3 that’s heavily modified as well. Swapped out mainboard with MKS GENL and TMC 2208 stepper drivers in stealthchop mode(sooo much quieter), TH3D firmware, E3D clone all metal Hotend, Bondtech dual gear extruder, MKS touch screen, Octoprint with touchscreen, powder coated PEI flex plate (never going back to any other build plate), EZABL bed leveling, etc. It’s a love/hate relationship for sure and I’m currently in love with it. Thinking of moving to a 32 bit board and new stepper drivers and will probably end up hating it again lol!

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[Robbob]

Originally Posted by KulaHI

I’ve got the Ender 3 that’s heavily modified as well. Swapped out mainboard with MKS GENL and TMC 2208 stepper drivers in stealthchop mode(sooo much quieter), TH3D firmware, E3D clone all metal Hotend, Bondtech dual gear extruder, MKS touch screen, Octoprint with touchscreen, powder coated PEI flex plate (never going back to any other build plate), EZABL bed leveling, etc. It’s a love/hate relationship for sure and I’m currently in love with it. Thinking of moving to a 32 bit board and new stepper drivers and will probably end up hating it again lol!

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Nice setup. Ive got the same board but not the drivers, I was curious about those. I got the touch screen too but gave up trying to finger it out. Best thing I did was the EZABL, its just so much easier.

[KulaHI]

Originally Posted by Robbob

Nice setup. Ive got the same board but not the drivers, I was curious about those. I got the touch screen too but gave up trying to finger it out. Best thing I did was the EZABL, its just so much easier.

The touch screen is nice but doesn't really replace the original screen as far as functionality. It does augment it nicely though. I usually have the original set to the babystep mode and the touchscreen I use for controlling movement and temps. It's been a while since I installed it but if you ever wanna try hooking it up again hit me up and I'll try and help you figure it out.

[Robbob]

Originally Posted by KulaHI

The touch screen is nice but doesn't really replace the original screen as far as functionality. It does augment it nicely though. I usually have the original set to the babystep mode and the touchscreen I use for controlling movement and temps. It's been a while since I installed it but if you ever wanna try hooking it up again hit me up and I'll try and help you figure it out.

Really appreciate that. I follow all your input in the 3D thread, very helpful all the time.

[Natedog]

Great looking build with your Capra based on 2.2s and handy 3D printing info! Where's this thing at now, get it out on the rocks yet?

[Robbob]

Originally Posted by Natedog

Great looking build with your Capra based on 2.2s and handy 3D printing info! Where's this thing at now, get it out on the rocks yet?

Thanks bud. Been practicing and tweaking it for the last couple weeks. Sheared a front portal gear so got the TGH ones in the other night. Hoping the weather turns warm again this coming week and I can get some video. So far winters just kept me indoors.

It has givin me time though to really dial in some things before the release comes along. Looking at an early April time frame.