View Full Version : Front chassi break

2011.01.06, 04:22 AM
Hi everyone,

Recently I have had two chassis break right in the front part. Just between the two springs in the middle of the chassis.
I've made a swap on the first one and glued back the second.

Does anyone have had the same breakage on his chassis?
I am concerned about the durability of this part of the chassis and the influence of it's break on the overall consistency of my car. Cause with this part broken, I'm loosing rigidity on the front of my car.
Is the SP chassis more solid than the black stock one?

Thanks for your help.

2011.01.06, 05:25 AM
At the track I go to I see about 1 broken MR-03 chassis per week in the non-burnable recyclables bin. That's just in the bin, so it probably happens more often. The track is carpet with unpadded wood barriers that are about 2cm high, so it's quite tough on the cars. There's a lot of horseplay and rough-housing also so this track might just produce a lot of broken chassis.

I break a MR-03 in the same fashion about once a month. This is a design flaw in my opinion, all impact stress gets transmitted into the area around where the body clip mounts, and with the way the front spring holder works, there just isn't enough material there (MR-02 is better in this sense). A bumper doesn't help either because it has to attach to either the body clip screw holes or the outer screw holes adjacent the body clip screws.

Bodies with strong noses exacerbate the problem (512bb, FXX and any car with a bumper). Also putting shims between the body clip and the chassis to lower the body mounting position makes it worse.

I know that's no help but in any case it's an 840 yen replaceable part, everyone just seems to laugh it off here. I'm sure there'd be less laughing if cost $15 or something.

I have both a black and grey chassis in my hands right now and I don't notice any difference in strength trying to twist or bend them. If you get a grey chassis and break it, just make sure to salvage the gold contacts!

2011.01.06, 05:59 AM
Cut up a fiberglass T-plate and shoe goo it to the weak part the next time you replace a chassis; should help with durability. I myself am not seeing this problem but I treat my 03 a lot more delicately than anything else I own...

2011.01.06, 07:30 AM
The first time I only notice the break after a while when I was working on my car. This was my car for the whole Belgian championship of 2010 without any problems so I wasn't too upset to break this.
Second time happens yesterday after a rather violent front to front impact on the mini-96 of my brother in law. It is on a limited JSCC chassis so it already has the gold contact. This is wy I glued it back rather than swap it.
The chassis is only a month old this time...

I suppose this problem is also due to the molding process of the chassis. On the two outside front holes used for bumper etc you can see injection trace, I suppose the plastic is molded via these outer holes and the two plastic injections come in contact in the middle of this area creating a much weak point. On my second chassis this part breaks in its exact middle, so where it is the much larger area...

I'll try to glue an old carbon t-plate right on this area I think... The chassis is about 20€ here(around 2000 yen, so twice your price:( ) so I prefer keep it longer than a month!

2011.01.06, 07:34 AM
I have been running the same SP chassis (gray) for over a year now without any problems. Maybe I am just lucky but, IMO the gray chassis are more durable. I am not sure why they are more durable though perhaps a softer plastic makes them more shatter resistant..

2011.01.06, 07:39 AM
Here's a pic showing the area that break (center) and the two molding trace (outside) on a SP chassis pic.

2011.01.06, 07:52 AM
Besides roasting one so bad the chassis warped, I am still running the same 3 chassis that I bought when the MR03s first came out. Two of the three are form the first production run with all the FET problems, and the third one was bought shortyl after. The newest chassis was burnt and replaced April of 2010. I run all three cars pretty much every week, and each one sees a race night about twice a month or so. Our group does run pretty clean, but I have been able to break a couple of pan bodies without losing a chassis yet.

2011.01.06, 09:00 AM
a good trick i do is make sure to shim a loose fitting body... make sure the front clip and side clips sit snug... if these areas allow for movement it will allow for more energy to impact the chassis... shim the body both foward and rear and side to side... this should help considerably...

2011.01.06, 07:32 PM
Here's a pic showing the area that break (center) and the two molding trace (outside) on a SP chassis pic.

If it breaks in the middle it's not a problem to glue it back together. A strip of medical tape and CA glue (my favorite repair method) will hold it. But after that, the whole front portion will eventually break off around where you put the other red circles. If it only breaks on one side, you can try to repair that too, but it is only a matter of time until it all goes.

Another failure mode is the body clip screw holes getting enlarged then stripped by multiple (tens? hundreds of?) medium to large front impacts. This can be fixed by filling the holes up with CA (not epoxy it's too hard), letting that dry an then tapping it out with a regular M2 tap. The coarse thread mini-z screws can take hold then. But again after this fix complete frontal failure is inevitable.

Like I said, it's a design flaw. But the Kyosho engineers (much smarter than me) made the performance/durability/cost analysis and that's what they decided.

If you will never use an upgraded spring holder/tensioner, I suppose you could glue that piece permanently in place with a strip or two of medical tape across the body clip screw holes and over the alignment posts (cut holes in the tape). WARNING: I AM NOT ACTUALLY AN ENGINEER! This should allow more impact stress to be transferred to the rest of the chassis instead of just those side areas.

I would try this buy I use the front inner tube dampers that have a metal spring holder, which isn't a replaceable part. So it's a 1,800 yen damper set versus an 840 yen chassis. Only the plastic pieces for the damper set are available as replacement parts.

The only real solution would be a soft bumper to absorb impacts. I guess just driving carefully and avoiding as many hard frontal impacts as possible is good too, but that takes away a lot of the fun.