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rc-martin

3d Printed HotShot Chassis

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Hi All,

 Thought i'd share with you all my project to build a 3d printed chassis vaugely based on the plans for a GRP chassis in a 1980's edition of Radio Race Car.

At the moment i'm just using PLA but will probably use PET-G or maybe ABS for the final print once I'm happy. It will most likely be a work in progress as once I've printed a part I usually realise what I could have done to improve it and go back and adjust the design.

The photos below show the basic chassis coming together and are already out of date as I've added some other features but haven't had time to take any pics yet.

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Started first by measuring the basic chassis/gearbox mounting locations

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Basic side section sketch in Autodesk 123D

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First print of many

One of the problems with the HotShot is it's unequal length steering arms and the terrible bump steer it has because of the steering linkage geometrey, this is something I wanted to improve. I've seen people using various bellcrank type steering and decided that I was going to use one too. I had a Tamiya M06 chassis lying around so I've utilised the steering assembly from this and added the relevant mounting block positions to the chassis base print.

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Tamiya M05/6 Steering assembly

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Side and base

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Improved steering geometry

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Radio fitted

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Love this! Great work. Have you considered making the battery compartment covered? I know a couple of people who can't run their Hotshot at the track because of the exposed battery. You could print one side of the chassis fully enclosed, and have a cover part from the other side? 

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Great work on this! This could become quite a popular upgrade for Hotshot drivers, especially with the incorporation of bell-crank steering.

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1 hour ago, ThunderDragonCy said:

Love this! Great work. Have you considered making the battery compartment covered? I know a couple of people who can't run their Hotshot at the track because of the exposed battery. You could print one side of the chassis fully enclosed, and have a cover part from the other side? 

Cheers,  my latest design uses a Tamiya M03 quick release battery holder but I've had to adapt this to use a modern square shaped lipo battey pack

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Spotted that you ran this at the Tamiya junkies day this weekend. How did it run? Was the new steering good? 

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On ‎3‎/‎11‎/‎2019 at 3:34 PM, ThunderDragonCy said:

Spotted that you ran this at the Tamiya junkies day this weekend. How did it run? Was the new steering good? 

Yes, ran at the Junkies meet. The steering set up works great, so much so that I had to turn it down because I had too much!

Discovered a few weak points which to be honest where quite obivious that it would fail in these areas but I've already addressed these issues in an updated version. The material that it's printed from is not ideal either so I'm going to change this also.

Got another couple of ideas in the pipeline for it too so should keep me busy for a while :)

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WOW, looks like a project that will keep improving with each generation.

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After beefing up the chassis I decided I wanted to tackle the suspension, I'd ordered a set of aftermarket Supershot shocks but didn't really want to mount them like they are on the SS, I've always loved the look of Grahoo's HotShot and wanted to go along the same lines, with front and rear twin inboard mounted shocks.

I tried as much as I could to mount the front shocks inside the chassis lowdown but the lack of space and poor geometry quickly ruled this out as a viable option which I think Grahoo may have encountered also and is why his car keeps the front mounted monoshock. The only other option was to mount them above the front gearbox instead, this worked out ok as I could adapt the front top suspension brace to hold the quadrants and create a shock mount that comes up from where the original anti roll bar bracket mounts are and still be able to fit a standard unmodified body. I also utilised the original pivot points but extended them like the Boomerang has, although I may change this again as I'm not 100% happy with it.

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Already redesigned the front suspension so the push rods are attached to the bottom arm, may move the pivot point further towards the wheel also yet. Also moving the front shocks forward so the cantilever is moving in a more linear motion and this also allows me to refit the original antiroll bar.

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This is one of the best upgrades I have ever seen. Freaking awesome. 

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On 3/19/2019 at 9:19 PM, rc-martin said:

Already redesigned the front suspension so the push rods are attached to the bottom arm, may move the pivot point further towards the wheel also yet. Also moving the front shocks forward so the cantilever is moving in a more linear motion and this also allows me to refit the original antiroll bar.

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Would love to see a bit of video of this compressing. I like a good pushrod! 

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2 hours ago, Pintopower said:

This is one of the best upgrades I have ever seen. Freaking awesome. 

Thank you! It's a great compliment to hear that from you, I'm a big fan of all your work too!

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21 minutes ago, ThunderDragonCy said:

Would love to see a bit of video of this compressing. I like a good pushrod! 

I'll try and get a video of it, I'm 99% happy with it at the moment now and am nearly ready for giving it a test run.

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Finally happy (i think) with the front end now, fitted new lower arm mounts with the pivot point further out and changed the shock mount position on the main chassis. The front shocks now can clear the anti-roll bar so it can be refitted. I've also mounted the shocks on a bar fixed between the shock mounts so this should strengthen those too, I'll cut some bits of aluminium tubing to go over the bar so it looks a bit smarter.

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Also took the plunge and bought the MIP diff kit

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