Sportsman + 3D print: Lil Doggy

[D440]

So I had a spare AR60 axle and a set of HB Rovers waiting for a long time to be used, and lately got into 3D printing, so I decided to embark myself to build a Shafty/Sporty/Sportsman (or whatever you call it) Comp Crawler.

My approach is to 3D print whatever is possible and go the DIY route as much as possible. Why? Because is fun as hell, and love to be able to change my rigs the way I want as much as possible.

So, I started researching for chassis options and look all the high-end brands and also found one in Thingiverse.com. I think the cleanest and overall best chassis available out there is the Succer Punch (from 5th Dimension), so I took the thingiverse chassis from here (https://www.thingiverse.com/thing:4337575) and took some inspiration from the Succer Punch to design my own.



After ~5 design iterations this is what I ended with:




I call it the Lil Doggy.

Got some parts to complete my build where I thought DIY was not viable:
* HR locked transmission
* Vanquish steering link
* Axial Hardline Body
* Que-T steel axle tube for AR60
* Dlux AR60 Truss Sporty Version
* Axial AR44 axle set (for rear)
* Crawler Innovation narrow foams
* Injora in-spring shocks
* Team Associated 16T 5-Slot motor
* HW 1080 esc
* Hitec D954SW servo
* Steering Knuckle s Weight from ebay
* For links I used spare traxxas ones plus built my owns

[D440]

While waiting for more parts to come, I had the first version of the chassis put together to see how it looks.



In this version, I had some issues on the links hitting the chassis and reducing articulation. Also realized that would be good to raise the upper arms mounting point in the rear AR44 axle.

[D440]

Designed a upper arm mounting for the AR44 axles.



Had like ~4 iterations to nail this one. Liked the result.





Finally, got the shocks, motor, esc in, so I put everything together for the first time. Used momentarily standard AR60 knuckles and some old wheels.

[D440]

Got the knuckles with weight - they look great and feel way better quality than expected.





I printed my final chassis version and replaced. This one is fixing clearance issues with links and adding some more mounting points to add cross members and have more room for link tuning.

[D440]

Next: wheels.

Started designing several wheel types and shapes. Wanted easy glue-on wheels and the option to add weight slugs too. Also not sure which width I'll go with yet, so designed wheel spacers of different sizes.



Works.



Then started to design a weight add-on holder.



Made holes for a standard 1/4" tube that you can find in home depot. Bought a Zinc Plated 1/4" tube and cut it in small 15mm pieces long.

[D440]

And this is how the weight add-on look. Again, went through like 4 design iterations to get it as small as possible.





Also had to design a wheel where these would fit. So started designing an glue-on inner ring wheel.



It's coming along.. the add-on weight have a great fit on the knuckles.



And the wheels fit with enough room for wiggle, so should work...



This is how the overall rig is looking at this point

[D440]

CI Foams came in today! (At last!)
Mounted the rear wheels and look great. The spacers in the rear wheels are .750" and with the 6.0 Narrow Comp Cut the HB tire is now a bit taller and thinner, just how I wanted.



In the front wheels I'm looking to try 0.500" spacers, so even thinner. Plus the internal ring mount system, I'll need to do some good trimming before mounting, to make it thinner and make space for the inner ring with bigger radius.


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[D440]

Getting to the "point of no return" now... Ready to trim the front foams.







Right wheel is 0.5" width and left is 0.75". Hard to see in the picture, but the thinner (right one) one is taller.

Wheels are done! Waiting for the glue to completely dry to test this thing!




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[HumboldtEF]

I love it, this looks like an awesome project.

I was planning to work up some slug holders pretty soon. Did you just make it a snug fit or are you gluing the slugs in place?

For cutting down foams I've designed a few 3d printed jigs that I stuff the foams into and cut them with a fine toothed hand saw. The hand saw does pretty well with the firmer foams, it only struggles with the soft outers but it'll do the job.

If you have any strength issues with the rear axle upper link extension you could try to re-print or redesign it so it (the upper portion) can be printed horizontally on the print bed, you get more strength from parts and holes that way. You could split the main mount portion from the side supports so they can be printed in the strongest orientation then joined with either CA or screws.

Sorry if this comes off preachy or something that was just what popped into my tinkerer head.

[D440]

Thanks for the tips Humbold, we'll see how it holds! And yes, I could make it beefer, but so far this PETG has been really strong. I'm more worried about the wheels to be honest, but we'll see!

About the weight holder, is printed in such a way that the weight cilinder fit REALLY tight, had to hammer them down! so they won't go anywhere..






Tested it for the first time, it's alive!





Also trying this lower battery mount, seems to be clearing just fine! I'll probably add more mounting positions to use bigger batteries as well (e.g. chassis and over the axle).



And the classic side test.

[Szczerba]

Really like all the parts on this rig! Nice work designing and putting it all together.

[Nova's Ark]

Nice crawler and build thread! Thank you for sharing your experience with the community. And thank you for your purchase of CI foams.

[D440]

Humbold had great eye catching the weakness on the rear axle truss. The thing snapped pretty easily after stress testing the rig.



So I re-designed it, making sure it would touch the surface below to avoid twisting back/forth. This resulted in not even needing the arms. Now is solid as a rock. Tested out, did some reckless driving and everything hold up great!





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[garyk]

Just stumbled across this, cool project. When I get some time I want to build a shafty comp crawler. I have a pair of AR60's laying around so will likely at least use one in the front, might have to get an AR44 rear axle like you did...seems to be a common combo. Good work!

[D440]

Thanks, Garyk!

Had some time today to work on the body and finish this thing up! The Hardline body is not as ugly as I thought, it's kinda growing on me

[D440]

The plated zinc knuckle weights were fun to build and worked great but turned out that I could actually use some extra weight up front. I got some tungsten weights from Amazon that were surprisingly cheap in the shape of 3/8" cylinders.

Went ahead and designed a new weight holder for the wider diameter one, where I could fit up to 8 cylinders, which is about 4oz!





Working to put this together and test it out.

[D440]

Did some little adjustments to make sure the Tungsten weights where fitting in perfectly and felt tight. Ready to test!

[D440]

My next step will be to make a high clearance diff cover. This has been way harder than expected, but is coming along. Inspired on the Progressive RC Barber AR60 cover (that dude is insanely creative). Don't expect mine to be as good, but functional.




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[D440]

Point of no return one more time! Designing this thing was way harder than I expected, but is coming along.









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[D440]

And..... Working! Still space for improvement tho



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