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Buggy Car Chassis Set to R/C

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Hey all,

I got this little educational buggy from Tamiya way back in July for my birthday in hopes to make it R/C :). My family asked me what I wanted followed quickly by a "no more R/C cars" policy, to which I requested this :lol:.

Starting off with the box:

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Opened with the few parts bags, instructions, etc:

IMG_07631.jpg

Various metal parts, battery holder, and switch (needed to be assembled):

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With most of the mechanical parts inc. the suspension:

IMG_07651.jpg

The assembled car minus the wires, battery box, and switch:

IMG_07661.jpg

And, assembled with all the components:

IMG_07731.jpg

After this, I had to decide on the layout of the chassis to fit the battery, servo, receiver, and ESC. I won't be using the standard AA battery box, and will be instead using 4 AAA batteries in series which will hopefully give a bit more power without a lot more weight added. The ESC will be a Duratrax mini one, and the servo is a Hitec HS-55. I'll be using an Airtronics AM mini receiver as well.

I didn't particularly like how the front had a massive offset, so in order to correct that, I've reversed the steering blocks and replaced the metal bar across the length of the bulkhead with two M3 screws. The 4mm metal spacers inside the trailing arms are from a Hornet, as are the black plastic nuts. The steering linkage was then too short, so I took some wire from a model airplane, and put in some bends similar to the original, but long enough to accommodate the new steering. This gives less offset at the wheels, and allows for more lock when the suspension is uncompressed (something the original suffered from).

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My hope with this is to keep the budget really limited, using common parts and simple means to make this radio controlled. I have no intention making this truly off-road worthy, as it'll mainly be used inside the house :).

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That's cute! It's like a little wooden SRB. Would running gear out of some RTR mini/micro car work? The little 1/24 or 1/36 Losi trucks maybe?

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Thank you all :)!

A Lego body would be awesome. My plan is to do something a bit different than an actual body shell, but maybe a mini-figure would look at home?

Ha, yep! I thought of a SRB too when I first saw it. I think micro/mini running gear would work great, like the Losi's you mentioned (although I don't have any for direct comparison). The only thing would be making sure the motor fits - it's somewhat keyed into the gearbox.

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That looks very cool. What are the dimensions of the chassis and wheelbase?

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This is so cute! At first glance, I couldn't believe it even has front suspension.

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Thank you both :).

Here are the dimensions for the chassis: overall length - 175mm, width - 105mm, wheelbase - 116mm (all approximate).

For sure! I was surprised at all Tamiya put into it. It even has a 'high' and 'low' gear selector at the back.

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I like the looks of this. Personally I would try to replace the wood with a fibreglass sheet chassis, or maybe even alloy or carbon, and go with the Mini Scorcher theme.

Perhaps a small static kit Beetle could be bajafied to serve as the shell?

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Thank you both!

Haha, pine car on meth :lol:.

I thought about a thinner sheet for sure and think it's a great idea, along with the Beetle body. The wood chassis is pretty thick and something thinner would be better. I think this time around I'm going to try to make it really basic, with the hope that anyone who would want to copy the idea could do so easily. In the future I might grab another one and go all out on upgrading it, though!

Some pictures for tonight:

Size comparison with a MSC resistor:

IMG_12111.jpg

Failed steering attempt:

IMG_12141.jpg

I took a piece of (brass, maybe?) metal and soldered it to the steering link to test it out. Sadly, when I attach a link between the servo and the post, under load the bar will deflect backward minimizing the steering. There's a lot of slop as well. On to a new plan I suppose. :unsure:

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Very nice build, looks very good.

Maybe you could use some parts from Mini-Z kits,to build a working steering...

Marcel

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Thank you both :).

It's a nice idea with the Mini-z - thanks! Fortunately I think I was able to get it to work a bit. I kept the same parts, only changed the way the servo mounted and it seems okay for now.

IMG_12191.jpg

I mocked up the electronics to see if I could get a running model - no luck. I was using 4 AAA rechargeables to power it and the ESC would just send the voltage directly to the motor - with the switch on or off! So, my guess is that because the voltage range for the ESC is between 7.2 and 8.4V it doesn't accept 4.8V as a suitable amount to power on the ESC? Not really sure. If I'm remembering right, when I did it with 6V it was fine. Don't exactly know how to approach it now - I'm thinking maybe add another cell or just run it off of alkaline cells?

Either way, it made me jump when I plugged in the battery and it came at me on full power! Ha, it's quick.

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How about foregoing an ESC completely, and using a servo controller PCB instead? With such light loads, it should work fine, and would be very small and light.

As for the steering, how about swapping the pushrod around so that the Z-bend goes through the servo horn and the clevis clips to the drag link? You could add a few thin shims to the clevis pin so that it keeps the drag link tag upright, and the extra thickness of the servo horn should keep the Z-bend more stable. Or if you use smaller clevises, you could fit one to each end of a short threaded rod for a very stable solution.

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I suggest using micro Lipo batteries and speed controllers intended for RC planes/helicopters, if space is an issue.

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Thank you guys! Great suggestions for sure.

XV, I decided to try out the servo idea - I had one cut up from a few years ago ready to be wired to a motor. Installed it, roughly trimmed it, and I had my first test run!

IMG_12221.jpg

Here it is all ready to go. It's not pretty, but I just wanted to see if it worked before I went through the effort of soldering everything. A few things became apparent as I drove. First, it's not as fast as I had imagined. When in high gear, it's respectable, but not quick. The turning radius is horrible, probably due to no differential and the huge offset on the front wheels. The drag link has a ton of slop as well; I turned the link around (which was a great suggestion), but I feel like the rigidity of the servo in contact with the clevis keeps it tracking more straight that if it was switched. Not sure how I feel about the drag link setup overall actually - there's a lot of weird camber and roll changes every time you turn.

It's heavy - even with twice the voltage than what is stock, it feels like the weight makes it slower than out of the box. I think the voltage is okay, but I'm hoping the motor can take more. Greg - thanks for the suggestion about the LiPo, I may end up doing that. Hopefully I won't need to do micro airplane electronics as well, but it's a good idea.

Overall, a good start though :). Some rough edges absolutely, but it was a great feeling seeing it run with R/C!

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