The Micro Shark Story + Production Chassis Build

[RexRacer19]

This thread is the story about how the Micro Shark rock buggy conversion came to be and a build thread about my personal, production chassis.

The backstory: For the longest time I have been a fan of rock buggies...not necessarily the Ultra 4 variety, but more like the W.E.Rock variety. Crawlers. I like the simple, bare bones style of them, and the fact that they really only serve one purpose, and do it well.

I don't feel like any of the RC companies have made a good, scale rock buggy effort. Some are close, but leave a little to be desired from a scale perspective. I get it though. When designing a kit for the masses, compromises have to be made to guarantee a durable product that can be manufactured by traditional and economical means. Even my scale centered effort has some compromises.

Inspired by the Vanquish Ripper I had the idea of applying a similar concept in designing a 3D printed rock buggy. Originally, I wanted to design it for a SCX10ii, but ultimately decided against it. I was concerned that even though it would be much cheaper than a Ripper, it would still end up being pretty expensive. More importantly, I didn't feel that it would end up being durable enough with the tube frame structure being a scale diameter. It needed to be scale or why bother?

Enter the SCX24. Once I saw this new chassis from Axial it instantly sent the wheels turning in my head. I finally felt like I could take the idea I had and execute it in a format that would work out on all fronts.

The number one goal for the project was scale. Without that, it would just be another bolt on chassis for a micro crawler. The initial challenge was picking a scale. After measuring up the SCX24 and looking at some dimensions from a 1:1 W.E.Rock buggy I eventually arrived on 1:20 for the scale. 1:18 might have worked also, but 1:20 seemed to work out better for frame rail width and wheelbase. Plus there are some nice 1:20 scale hardbody options for micros. Would be kind of cool seeing them wheeling together on the trails.

With the scale decided, I set out on the design process. I spent a couple of months designing the conversion parts which included reverse engineering the SCX24 frame and key components. For reference my design is heavily influenced by the Goatbuilt JHF pro mod buggy kit and also draws from other designs that I like. It doesn't replicate any specific vehicle exactly, but is dimensionally accurate to what the "standard" overall dimensions would be. A lot of these buggies look similar, but each one is unique in it's own way...this is how I would build my own 1:1 rock buggy. Once I was happy with the design of things, the prototyping process began. This is still a spendy package of parts to produce, so I wanted to get it as right as possible on the first try, then hopefully only make minor revisions beyond that. It's a lot to "get right" but feel like the first iteration worked out pretty well. Here is Micro Shark prototype number 1 all painted up and assembled.










Everything fit perfectly, but I did learn a few things that I wanted to do differently. Originally I had planned on making the hood and fuel cell cover attach with little magnets. This idea worked out functionally, but the magnets were another expense for the user and were a little tedious to install. I decided to make the hood attach with clips and the fuel cell/cooler attach with two screws. I didn't like how the initial battery tray left the battery and some of the wires visible so I integrated it into the tube frame and covered up the sides more. I added some wire routing and a few more details to the chassis like the sheet metal and expanded metal flooring. I also learned that I needed to split the interior parts in order to make it easier for painting and installing into the chassis.

With all those changes made I decided to print another set of parts that would hopefully end up being production parts. The first prototype was based on a Suzuki Samurai. I had already modeled up a Samurai body for another project (that never got finished) so I used that for the first build. I went ahead and designed a FJ40 hood and grille along with matching side panels for the second go around. Eventually I plan to do a Jeep body set and possibly others. Here is the full set of parts from prototype 2.




I will be documenting the painting and detailing of this chassis moving forward in this thread. With the exception of a couple details added to the main chassis it is essentially a production build; the same parts everyone gets when they order the kit.

[spoo76]

Awesome, the nerd in my appreciates the back story

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[jimbo74]

Rex19, you are mod19rc?

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[spoo76]

Originally Posted by jimbo74

Rex19, you are mod19rc?

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I think his post and screen name would say yes haha

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[RexRacer19]

Originally Posted by spoo76

Awesome, the nerd in my appreciates the back story

I figured some folks would appreciate it.

Originally Posted by jimbo74

Rex19, you are mod19rc?

Guilty as charged.

[GChambers]

Love this thing, Jeff. Great work.

I'm gonna have to break down and order one soon.

You still playing with any of the 1:1 cars?

[PileDriver]

Nice article. Thanks for taking the time to provide us with such a great scale product.

When do you plan on doing the Jeep style and will it look similar to the Ripper?

[RexRacer19]

Originally Posted by GChambers

Love this thing, Jeff. Great work.

I'm gonna have to break down and order one soon.

You still playing with any of the 1:1 cars?

Thanks, Geoff. No rush...they will be ready whenever you are.

Not so much on the 1:1 stuff. I sold the drag car right after moving to NC several years ago. I bought back Cupcake (Locost 7) a couple of years ago, did an autocross event, made a giant list of things that it needed done to it, and haven't touched it since. Maybe I will try and do something with it next year. Too many other things that require time...

Originally Posted by PileDriver

Nice article. Thanks for taking the time to provide us with such a great scale product.

When do you plan on doing the Jeep style and will it look similar to the Ripper?

Thanks for the kind words. Had to take a little breather after the launch, but I am hoping to get the Jeep version out by Thanksgiving. I don't think it will look exactly like the Ripper. The hood will probably be a little more pie cut and narrower up front.

[GChambers]

Originally Posted by RexRacer19

Not so much on the 1:1 stuff. I sold the drag car right after moving to NC several years ago. I bought back Cupcake (Locost 7) a couple of years ago, did an autocross event, made a giant list of things that it needed done to it, and haven't touched it since. Maybe I will try and do something with it next year. Too many other things that require time...

I still have a strong desire to build a Locost. I've often thought that just doing an Exocet chassis on my Ecotec car would be a better and much easier plan and maybe satisfy that desire a bit but I really want to build something from the ground up just to see if I can do it.

Anyway, back to the Micro Shark... The cage material. As far as durability, how big of an impact do you estimate it would take as far as drop height?

[RexRacer19]

Originally Posted by GChambers

I still have a strong desire to build a Locost. I've often thought that just doing an Exocet chassis on my Ecotec car would be a better and much easier plan and maybe satisfy that desire a bit but I really want to build something from the ground up just to see if I can do it.

Anyway, back to the Micro Shark... The cage material. As far as durability, how big of an impact do you estimate it would take as far as drop height?

It can be pretty rewarding to build from the ground up, but man there is so much time to be invested. The Exocet would be the easy button for you for sure. I am guessing there is still a lot of work involved to do it right.

So most all of the parts in the Micro Shark are made from Shapeways' "strong and flexible" material. It is a laser sintered nylon and as 3D printed materials go, it's one of the strongest plastics. I'm going to give somewhat of a non-answer here, and say it depends. By designing it with scale accurate tubing diameters there is some compromise in strength. I think it can take some tumbles and maybe a few good falls depending on what it lands on and how. If you take a header from a table and land nose first on a hardwood floor, I wold expect something to break up front. Landing on the roof or side might turn out better, but without trying to purposely break one in various ways, it's hard to say for sure. I've put a disclaimer on the build guide that if you want to full send, cliff dive, rock bounce, etc. do it at your own risk. This is a scale rock buggy...those guys go slow.


On with some building...

The first order of business is painting the tube frame chassis. I have just gotten into the habit of painting pretty much everything I get from Shapeways. The dye that they use can scrape off fairly easily and the porous nature of the parts makes them hold dirt easily and become hard to clean. Painting gives the parts a consistent color, seals up the porosity, and makes them hold up better (color wise) after some abuse.

Here is the frame after three coats of Krylon Fusion matte black.








Painting smooths up the surface of the parts, but doesn't remove the texture completely. It's easy to fix on large, flat parts, but there isn't much more I can do to improve the surface finish on all these little scale tubes.

I feel like I need to make a smaller scale garage for this build...but I can't even manage to finish up the 1:10 garage. :laugh:

[PileDriver]

How much does this kit cost?

[RexRacer19]

Originally Posted by PileDriver

How much does this kit cost?

If you buy everything including the interior parts it ends up running around $160-170 to do the conversion, plus the cost of your stock SCX24 Deadbolt.

[PNWRC]

My favorite mini, great work man!


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[RexRacer19]

Originally Posted by PNWRC

My favorite mini, great work man!

Thanks, man. I appreciate it. Love seeing your build and so many others coming together.

I haven't been doing very well on making progress with this new build, but have some updates to share. I was able to get the painted frame assembled with the chassis and squared away.






It's kind of cool seeing this one going together along side the OG chassis. It's just what I would expect walking into a Micro Shark fab shop.




Next I went ahead and put the suspension, axles, and tires under it to make it a little easier to push around the shop while it's not getting worked on.








I don't plan on using the stock electronics on this build, so I set out on sourcing some good micro sized components. I found an awesome micro receiver that binds with my favorite Sanwa MT-4 radio. It was only $35 on top of being micro sized. It does require that the plugs either be changed or an adapter made for the servo wires no big deal.

I took a gamble at an inexpensive 10A esc that didn't pay off. Despite being only $10 and being really small, it had worse low end control than even the stock ESC/RX unit. Plan B I guess is to use a Castle Sidewinder Micro. I will end up having to rewire all the leads and whatnot to ensure it fits, but I think it will work out.

Here is the receiver and 10A ESC that I originally wanted to use.

[GChambers]

Jeff, did you buy that one from Amazon?

[RexRacer19]

Yes, it's the Amazon one.

[GuyOverThere]

This thing is super sweet I will likely pick one up. I was curious if your cage design could support 4 wheel steering?

[RexRacer19]

Originally Posted by GuyOverThere

This thing is super sweet I will likely pick one up. I was curious if your cage design could support 4 wheel steering?

Thanks!

Unfortunately it will not support 4-wheel steering. The rear servo would be up into the electronics area unless the ride height got jacked way up.

[GuyOverThere]

Originally Posted by RexRacer19

Thanks!

Unfortunately it will not support 4-wheel steering. The rear servo would be up into the electronics area unless the ride height got jacked way up.

It's all good. I was just thinking 4ws would make this thing the ultimate apartment crawler. Have you found if it works with the jeep version of the vehicle as well as the dead bolt yet?

[RexRacer19]

It would be cool for sure. It's just hard to package it in for this style of chassis.

Yes! You absolutely can do the conversion with the Jeep now. It is outlined in the product info. You just have to select a different tree of parts for the Chassis Components that have the longer rear links included.