The Frogtima build continues... Several more updates:
As mentioned, the lexan body that I hacked up for the Frogtima came with a spoiler. After some deliberation, I decided to channel The Frog a bit more and go for it.
After some searching around, I ordered an Associated B64D Wing Mount, and realized I could couple it with this optional chassis piece from my original Frog (I added the aluminum spacer):
Those two pieces fit nicely against the rear Optima shock mount, fastened with a long M3 screw:
It looked like it was meant to be.
I then cut and painted the spoiler, and attached it:
Voila! I prefer the look with a wing. It's less traditional Funco, but imo the proportions are better this way, and it looks more bratty.
I also swapped the aluminum Scorpion top for one I cut out of spare lexan. Some stress cracks are apparent after the heatgun bending, but I don't mind much. I am sure there will be more to come.
One bonus of adding the wing was the ability to sport the Frog's "No Guts, No Glory!" motto :
After adding the wing, I found an interesting way to simplify the top of the Optima gearbox/Frog chassis connection.
Some time back, I ran some bars between the shock mounts and the rollcage:
However, I still had some roughly cut carbon fiber panel pieces spanning the Optima gearbox to the Frog chassis. It wasn't elegant, I didn't like it, and became a bit less necessary with the mount/rollcage connection.
Adding the wing mount created an opportunity to replace them.
I had a bit of angled black aluminum tubing with a M3 thread. With a headless M3 screw, I capped the tubing with a steering link that fit snug around the rear aluminum cross bar. I then threaded the screw running through the wing mount into the other end of the angled tubing. It was a perfect fit.
I was able to remove the panel connections, and it stabilized the wing mount to boot.
I also completed the decals.
Except for the numbers, which are from the GMade R1, I went with Frog decals from MCI. I gave the Frogtima the number 210 as an homage to its Optima roots.
Following all that, I read this article about dual rate springs.
I went with the dual spring shocks for looks, and because it was my intuition that two spring rates would improve handling (soft springs for less travel on small bumps, hard springs for more travel on jumps). However, according to the article, you need either binding (full compression) of one spring, or a cross over ring to limit travel of the spring divider to get the benefit of dual springs. This from an ORV:
Dual spring compression is very interesting. Say you have two springs, one with a spring rate of 100, and one with a spring rate of 200. What is their combined spring rate if you stack them? You might think that it would be somewhere between 100 and 200, but noooo....
Dual spring rate = (SR1 * SR2) / (SR1 + SR2)
So, the combined spring rate of the 100 and 200 rate springs would be 66.7. Pretty interesting, I think.
Anyway, the Team Raffee double springs I installed on the Frogtima had the divider, but no cross over ring. Using short soft springs for the top of the front shocks, I was able to get binding when the springs are about half compressed:
This results in genuine dual spring rate, which you can feel.
However, I didn't have long enough lower stiff springs to achieve binding of the top rear springs...
I am pretty proud of this little mod: I created a cross over sleeve (instead of a cross over ring), for the rear dual spring shocks.
After waxing on the cross-over ring a bit, I decided that some large heat shrink tubing might do the trick.
Cut and shrunk:
It fits nicely under the spring, but stops the collar:
Stopping the collar:
And the bottom spring compressing only:
Genuine dual spring rate action!
Also, the heat shrink sleeve slides down if needed, so I can still use the top adjustment screw to tighten or loosen the shock.
I am now looking at all the single spring buggies out there with a skeptical eye... Even the competition buggies are using single springs. They must be using hard springs, otherwise they'd bounce when landing a jump. However, tracks aren't perfectly flat, and hard springs will result in vibration and reduced friction when quickly going over a slightly uneven surface. Could it be that competitive buggies are missing out on such a potential advantage? Should I quit my day job and become a professional RC buggy racer?
More to come.