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View Full Version : Arm Strong or Strong Arm?


Skv012a
2009.04.20, 03:22 PM
Whoever bothered checking my youtube for CW hfay s7r4 vid would know that my 15 suffered a deadly blow to the front arm, at its base. I despaired at first, but came up with a perfect fix for such AND a great reinforcement plan for anyone who is concerned about this and doesn't want to shell friggin 22$ for alum front tower bars. With only +0.25g per each arm, here she is:

http://i452.photobucket.com/albums/qq249/skv0124/MiniZ/MR15-ArmFix1.jpg
http://i452.photobucket.com/albums/qq249/skv0124/MiniZ/MR15-ArmFix2.jpg
http://i452.photobucket.com/albums/qq249/skv0124/MiniZ/MR15-ArmFix3.jpg
http://i452.photobucket.com/albums/qq249/skv0124/MiniZ/MR15-ArmFix4.jpg
http://i452.photobucket.com/albums/qq249/skv0124/MiniZ/MR15-ArmFix5.jpg

2mm thick styrene piece drilled and cut to fit for most effect and hug. Glued with Kyosho glue to get that "soldered on shut" feel when all is said and done.

hrdrvr
2009.04.20, 07:16 PM
Good fix. For those looking for more bling, and less time invilvoed, PN sells a product thats is practicaly the same, but made out of SSG. I think its sold as a reinforcement piece though, rather than a replacement. I would be nervous about getting the front end properly aligned, but I have seen it done successfully.

color01
2009.04.20, 07:16 PM
Atomic. ;)

Skv012a
2009.04.20, 07:33 PM
Good fix. For those looking for more bling, and less time invilvoed, PN sells a product thats is practicaly the same, but made out of SSG. I think its sold as a reinforcement piece though, rather than a replacement. I would be nervous about getting the front end properly aligned, but I have seen it done successfully.

Well, I kept alignment in mind and thus superglued the arm back while it was still held on by the pin. I figured kyosho stuff might melt it and cause misalignment, so I saved it for the extra pieces. If your arms aren't broken yet, just glue styrene on and never worry about this again.

As far as anything similar that can be bought, thats exactly my point- can be bought. IMO whenever you can make something good for free it beats buying. Also, thickness helps in this case and I can't even imagine how the SSG stuff would stay on(glue it on or what? can you even glue that stuff to abs?).

arch2b
2009.04.20, 07:42 PM
good idea, it's been done before. atomic sells carbon fiber pieces similar to yours.

while like the idea of reinforcing, your relying on the glue bond more than the structural stability of the plastic. as i opinioned on the atomic parts, your just going to pop these off likely. i guess it's better to pop this off than break the arm though.

Skv012a
2009.04.20, 10:55 PM
Seeing how its not glued with superglue and it doesn't receive head-on impacts that much, I don't really see a problem with this fix. I have a feeling that my stock snapped after 2 months of rolling and etc on top of the stock arms on 15 being pretty thin and rigid rather than a little flexible. We'll see.

Eman
2009.04.23, 12:21 AM
I've found if your wheels and tires don't extend out past the body at full lock you can avoid ripping off the lower control arm. Of course you'll want to reinforce your body with some CF. Atomic makes some pieces you can bond on your body or you can make them yourself. I couldn't find the video so I couldn't see exactly what happend. PN makes the lower bar for the MR-02 / MR-015 body conversion that should work on MR-015, but like you said there is the cost to consider. Atomics CF reinforcement looks like it would work but I wonder about the area around the king pin. Its very thin and not covered by the reinforcement. If you were to clip a corner again you may not remove the lower arm completely but that force would have to go somewhere. My guess is the thin area around the bottom of the king pin. I like shiny so I would pop for the PN pieces.:)

Skv012a
2009.04.23, 07:46 AM
Actually, the way the lower arm is made is very sturdy. I also don't see the pin holes breaking because they share impact among themselves. The top arm however, especially on a 15, is the most fragile and the longest part and receives the most impact. All my bodies protect my wheels very well, but my car still flips to a degree and thus wheels somehow take their toll. It could've been a collision's fault too, but who knows.

One more argument against PN's MR15 > MR02 width front bars is just that- they're not MR15 width and I honestly don't see a reason to make 15's front wider. I'd just use an 02 if I wanted a fatter car/stance.

soyverde
2009.04.23, 08:51 PM
Actually, the way the lower arm is made is very sturdy. I also don't see the pin holes breaking because they share impact among themselves. The top arm however, especially on a 15, is the most fragile and the longest part and receives the most impact. All my bodies protect my wheels very well, but my car still flips to a degree and thus wheels somehow take their toll. It could've been a collision's fault too, but who knows.

One more argument against PN's MR15 > MR02 width front bars is just that- they're not MR15 width and I honestly don't see a reason to make 15's front wider. I'd just use an 02 if I wanted a fatter car/stance.

I've never seen a lower arm break, the upper is definitely the one to deal with first (had several crack over time). This setup is probably just as good as the CF reinforcement (might even be better, who knows), but I am surprised you didn't spring for a new chassis at $9-$10, just so you know the geometry isn't messed up. If there is one thing you need to worry about, it's all the flipping you're doing. You certainly seem capable of putting down a decent lap, but at the rate you are rolling that chassis it is hindering you and everyone else on the track. You're not helping anybody if you can't keep your car driving on the track and in one piece for more than a couple of laps. ;)

Skv012a
2009.04.23, 10:22 PM
Hence why I got new 90mm MM and am rolling out AC Cobra. I just don't see this combo failing because there won't be any heavy weight shifting across the whole chassis (due to lack of a rear mounted motor) nor will there be any roof/huge plastic glass weight to raise CG. Now that I also evened out the front/rear stance width, it should be as solid as ever. Very lastly, assuming it won't flip and hypothetically assuming I can keep up with it, 166 grams should finally give you guys some competition.

Eman
2009.04.23, 11:20 PM
It doesn't make it wider. It makes an MR-02 narrower. So you can use narrow bodies. The lower arm has the same distance between mounting holes so it should work on MR-015. The upper bar wouldn't work. The distance between mounting holes is greater. Yeah the only cure for breaking arms due to rolling and flipping the car is to stop. :D

Skv012a
2009.04.24, 12:31 AM
02's bucket can't physically fit under MR15-only bodies. What were you referring to?

soyverde
2009.04.24, 07:42 AM
Hence why I got new 90mm MM and am rolling out AC Cobra. I just don't see this combo failing because there won't be any heavy weight shifting across the whole chassis (due to lack of a rear mounted motor) nor will there be any roof/huge plastic glass weight to raise CG. Now that I also evened out the front/rear stance width, it should be as solid as ever. Very lastly, assuming it won't flip and hypothetically assuming I can keep up with it, 166 grams should finally give you guys some competition.

I saw the 90mm MM post/pics after I made this post. Very interested to see how the new pod handles, and the ringer has had decent luck with that body (though it's still prone to flip once in a while). I hate to see you dismiss anything with a wider rear track out of hand, though. Something along the lines of a Testarossa or Corvette would probably run quite nicely on an 015 (very nimble) with a lot less tendency to roll in fast sweepers. You certainly don't have to stick with the stock front offsets, either (I tend to go narrow, even run -1's on my McLaren). It's pretty hard to set up a single chassis to handle all track layouts well.

Skv012a
2009.04.24, 08:59 AM
I placed 1st @ Awesome 1 day when I used Testa, but it wasn't as fun. There was no real tuning involved behind that body combo. I'll move up to 02 in due time, you gotta remember I'm only couple months into these and simply lack raw experience.

As far as track handling, I think tire combos and front springs can take care of that. I'd rather the stance remain the same for 1 more reason- see whats different per track based on the car's behavior. Since we mostly do 2 wide Ls, this guy proved to be capable already so the only real question is a real high-speed track.

One last thing I keep wanting to get is a set of non-dish alum rims w/ my preferred offsets (N+1 W-1) to add the most effective ballast right where it's needed.