| Author | Message | ||
     Knickers |
Does anyone out there do anything to make the XB-R "crashable" as in drilling out subframe mount bolts or notching the subframe in some manner so it doesn't break the frame on impact? I broke off the subframe mount lugs in a crash last year that put me out of commission for a while.  The bike is for track only and I picked up a spare subframe so I don't mind cutting it, just looking for what may have worked for others. TIA Kurt | ||
| Slaughter |
I'm looking at trying to resolve exactly that issue. Destroyed my chassis in my last get-off so I'll be able to use it as a fixture. Will be making a seat with no subframe. If it works, it'll be sold through Glendale. Shoot me a note, I'm assuming this is a racing application? You'd need to re-mount everything that normally goes under the seat. No guarantees... short on spare time but it is something I'd wanted to do for a while now. | ||
| Knickers |
Interesting, a seat with no subframe. I suppose you could also just cut the subframe aft of the seat. That could leave the battery tray and shock reservoir mount but take away the tail end which might reduce the chance of an impact breaking the frame. I was thinking perhaps you could weaken the mount bolts enough so they fracture on impact and save both the frame and subframe. I wouldn't want to be the first one to try it though. But if you come up with a system - I'm interested. | ||
| Benm2 |
What about making a semi-fabricated subframe from some carbon fiber tubing & some custom machined aluminum bits? If there were spots to mount the racing-necessary hardware, you might be able to make it so individual tubes could be replaced. Another option would be to make the connection to the frame stronger, by using a 6061 or 7075 mount that bolts to the frame using the existing mounts and maybe an alternate stiffening point or two. THEN modify the stock subframe to attach to the new bit. The net effect I'd be looking for would be to move the failure point from the main MC frame back to the subframe. | ||
| Slaughter |
Kurt - the Rich Conrath subframe is pretty much as you described and yes indeed, it wouldn't put as much stress into the mounts if it were half the length. Because I actually DO composites for a living, it obviously colors my thinking. Ben, you're absolutely right - and I had kinda/sorta looked as tabs that bond to the seat and bolt into the mounts. A flipping type wreck would tear the seat to bits, NOT the mounts. Actually, I haven't seen the mounts tear out, mostly I've seen the subframes break. I ought to take a pic of my latest "subframe modification" done in Turn 8. | ||
| Knickers |
I wouldn't mind so much if just the subframe would break. That's got me thinking, maybe all I need to do is cut some notches into the subframe just aft of the seat. If it takes an impact back there where the leverage is greatest it should just snap the subframe. Any impact from the seat forward probably won't have enough leverage to tear out the mounts. | ||
| Slaughter |
That makes sense. Mine folded up the last time (still didn't get a pic yet - it's in the truck bed at work, not enough room in the garage) | ||
| Slaughter |
The way mine tore off is actually about where you can cut it off (just don't ride a passenger):  (Message edited by slaughter on April 25, 2008) | ||
| Knickers |
It looks like it took an impact from below, maybe that's why the lugs held and the subframe broke. Mine slid into a berm and took an impact in the passenger seat area.  | ||
| Slaughter |
Kurt - that's exactly what happened. Bike tumbled about 4 times end over end... probably about 120 mph. Landed on the rear wheel and tore the engine/chassis apart. I think you could easily cut off the back of the subframe truss and just eliminate it altogether. I can see how yours tore off the mounts with the side load. Taking off that 14 inches or more of subframe cuts the moment in half (or better) - at least that would be what it looks like. I will be doing the seat with integral mounts and no subframe - just to see if it works out OK. It will be slow going since I'm still just barely started tearing the engine down to smallest pieces to combine it with a new engine that I'll be spigot-boring in the coming month. I guess the custom bodywork is going to take second place to the basic bike reconstruction... especially since I still have the stock seat. | ||
| Kenneth |
happened to my bike twice...had the frame welded back thicker...cut the subframe...hasn't happened since | ||
| Slaughter |
What Ken said just makes sense. Cut the subfame where you see mine bent up and it'd still take the weight of your butt and not have such a long arm. If you have a good welder (aluminum) you might be able to have him weld more meat onto the mounts and then you could drill/tap them out. (I hate losing arguments with gravity.) | ||
| Knickers |
I wonder if that would still square with WERA's requirement that the tail of the bike extend over the rear axle when its just flimsy fiberglass extending that far out from a cut subframe. I'm guessing that requirement is written with the idea that they don't want road debris to be able to get kicked up by the rear wheel and hit the rider. | ||
| Slaughter |
WERA west would have no problem with it. I don't think that the section of rules has anything other than road splash in mind. MANY people use short subframes since they're re-locating batteries forward and lower anyways - and they just don't want the subframes to tear chunks out of the chassis. (not like that ever happens!) Conrath used to sell one but it was VERY pricey. Better getting an ebay version and using a hacksaw and 10 minutes. Basically that's my lazy-man's approach until I get the "plastic tail" built. | ||
| Knickers |
Thanks for the advice Steve. Hey here's an off topic question. What are your thoughts on running without at BAS sensor on the track? I'm in the middle of replacing a broke fairing bracket and it looks like I can ditch the headlight bracket if I lose the BAS. I'm assuming I can just solder the sensor input to either 5V or ground to bypass it. I don't think I'd want to mount it elsewhere since it looks like it has nice rubber isolators for the bolts in the stock location. I'm just looking for more parts to strip from the bike. | ||
| Slaughter |
I have mixed emotions about the BAS. I took mine off and one time got punted to the outside and as I'm lying in the dirt, kinda becoming aware of my surroundings (before the crash truck arrives), I hear the bike still running and run over to shut it off (a no-no actually on a hot track but it was a track day, not a race and the bike was about 50 feet off the track) I'd be concerned about these dry sump engines running without oil. I know that's not exactly an answer but I think that when I finish my rebuild, I may put the BAS back into the system. (Message edited by slaughter on April 26, 2008) | ||
| Kenneth |
I cut mine right where yours is broken...takes away the leverage it the bike flips...and sacrifices the much cheaper bodywork and saving the costly subframe and frame...ASRA and CCS florida didn't seem to mind at all about the subframe. As far as the BAS...even if the bike is on it's side...I doubt it's running without oil...probably not too good for venting though. These things are surprisingly good about not needing a whole lot of oil... I've wasted some oil pumps and the engine be fine. |
