Tweaking The Mystery Machine

[Frankentruck]

I didn't build this rere Lunchbox, but I've been enjoying it enough to want to make some improvements.
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If it stayed stock, I wouldn't see a need for a more powerful motor. That would be phase 2, if warrented by improvements in steering and suspension.

[Frankentruck]

Starting with centering the steering servo. Printed ABS wedge and oversized square servo mount blocks. The chassis width is perfect for centering a standard size servo.
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The CRP kit arms are meant for an FX10 and the pivots are a little long for a Tamiya. A little trimming will take care of that.
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After some trial articulation, it looks like the Tamiya servo saver doesn't provide enough movement. A bigger servo saver with more swing is needed.
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Some printed upper control links, control link mount block, rear wheelie bar rollers, and shock cups for some oversized springs. Also some longer 56mm turnbuckles, if needed. The pair of 52mm turnbuckles that replaced the stock 104mm total length of tie rods seems a little short for this suspension setup.
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[juicedcoupe]

I use these in my Tamiya ORV's. I actually prefer the ball stud placement, compared to a Kimbrough.

https://www.amainhobbies.com/traxxas-large-servo-saver-tra1844/p14843

[Frankentruck]

I had the Kimbrough on hand. If it doesn't work out, I'll give that one a try. Thanks for the tip That also might be what I need when I get around to re-doing my Hyper Hornet front suspension.

[juicedcoupe]

That also might be what I need when I get around to re-doing my Hyper Hornet front suspension.

I hate dealing with the limited clearance in Hopper tubs. I just use the standard servo saver and glue it together, then use a cheap metal gear servo in it.

But with your printing capabilities, you have a lot more options than I do.

[Frankentruck]

That also might be what I need when I get around to re-doing my Hyper Hornet front suspension.

I hate dealing with the limited clearance in Hopper tubs. I just use the standard servo saver and glue it together, then use a cheap metal gear servo in it.

But with your printing capabilities, you have a lot more options than I do.

It there's something you need printed, I do take occasional requests.

For the Lunchbox, the fixed length upper links are not quite the right length so I'm changing out to a hybrid with a ball end and threaded rod.
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[Frankentruck]

The front suspension is close to ready, but the shock mount points in the arms are a little to far inboard. I need to make some adapters to move them outboard about 1/4" (not as far as the loose ends in the picture). My new shocks also don't have enough threaded stud length on top for the chassis stabilizer so I'll need to pick a new spot.

56mm turnbuckles had to be used instead of 52mm, and they could have been a little longer, but should work well as is.
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The rear shocks look like they'll do a good job, but the springs might be too stiff. i have a good selection in this size so I'll experiment a little later. It would be nice though if the gearbox had a pivot ball like the Traxxas Cat instead of this fron sliding slot arrangement. I've seen the '5th shock' mod setup. That might be what I go with. Maybe.

Bigger wheelie bar rollers added. If they don't control the back flips, I'll look into a longer arm.
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[Frankentruck]

The brackets for the front lower shock mounts worked out well. For the upper brace, I modified the ends to have hex pockets for the shock stud nuts. Both solved the front end build problems and the front suspension moves in a normal, predictable manner. The steering throw with the bigger servo saver is just how it should be too.
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For the rear, I didn't like how the front pivot tucks and sorg of binds the right rear shock against the motor. For now, I added a lockout that I designed for the Hyper Hornet. This is a temporary fix that makes the rear suspension work like on a Grasshopper. It will be good enough to get me back running again while I think about the rear more.
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[Frankentruck]

It's a much improved runner and a satisfying basher. The steering is good, the wheelies are not overpowering and have sort of turned into a sprinter/chock style launch, and overall it's a lot more stable. I think it's pretty much done, at least until some way to better control the gearbox pivot comes up. I think the stock 540 motor works well with it too. It seems 'right powered' on a 2s pack, not over or under powered.
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[ZED32]

I have the ampro transmission brace on my hornet and it's fantastic. Keeps the "rolling" axle function but fixes the slider issue. He makes one for the lunchbox as well since they utilize the same transmission.

[Frankentruck]

I thought about something similar to that ampro brace bracket, but after looking at how the gearbox should be allowed to move I think there might be a better solution. That is likely better than my current pivot restrictor. Thanks for the suggestion.

[1911Colt]

That is very slick! I would be tempted to swap out (or paint) the yellow wheels for something a little more Scooby Doo-ish.

The front upper control arms are brilliant. Such a simple solution.

Just curious, do the front wheels gain positive camber as the shock compresses? It might just be the photo, but they appear to angle down (higher at the frame, lower at the hub). It won't matter on a monster truck, but this is one of the first mods Shelby made when Ford asked him to get the Mustang ready to race, so it caught my eye.

[Frankentruck]

It's probably photo distortion. I fight a losing battle on that with cell phone photos. Also the front shocks are at an angle that might give that camber illusion. At no compression, camber is neutral. At maximum front shock compression the camber goes 1or 2 degrees negative. With the front shocks disconnected and front arms hyper drooped, it would have positive camber.

Didn't paint or do the original build (civilguy sold it to me) but in the pics I've looked at of the Mystery Machine some have green wheels and some have yellow. What I feel it's missing is the orange wheel flowers. I've thought about how I might make those. Orange decals are the leading contender right now.

[Frankentruck]

I got to do some running with the Mystery Machine today. It seems to be a pretty competent basher now. I have a plan for how to add some controlled gearbox twist but its low priority. I don't feel like it will enhance the running very much. However I do notice that the gear diff transitions to 1 wheel spinning really easily. It would be nice to have a ball diff with adjustable tension. Probably not a possibility though.

[juicedcoupe]

Lock the diff. On a Lunchbox or hopper, the pros outweigh the cons.

I think that you can download the plans online and print it yourself.