Bike in half and on fire

[Janne]

http://www.vitalmx.com/forums/MotoRelat ... ire,904409

[AlisoBob]

NASTY!!!!

[hoofarted]

That is just terrible:





So this is the second AF death I've seen on the web. Notice that they're snapping at the spars and top of the Y? Was this shoddy workmanship? WTF?

[AlisoBob]

The same recessive gene thats causes the British to have nasty teeth, appearantly hinders their welding skills as well....

[ZETTNORCAL]

I saw one get welded up with a billet Y just the other day. The guy just went ahead and started tig'n the solid Y to the tubing

When I built mine I reused the Y (crf250). I used solid square stock for the extensions and machined them to fit into the stock tube cradle. But when I welded it I preheated the solid stock with the torch to I,m guessing around 450 -550 degrees? Before welding it to the Y and the stock tubing.

Looks like thease bike that are braking in half were not properly welded at the Y section, and it seems that they all had solid billet Y's

[yota]

it amazes me that neither of these guys got hurt.

[redrocket190]

The same recessive gene thats causes the British to have nasty teeth, appearantly hinders their welding skills as well....

You have confused genetics with socialized dentistry. I had to go to a US dentist to discover you can have anesthetic when you have your teeth drilled.

[AlisoBob]

You have confused genetics with socialized dentistry.

Genetics..... 110%

[redrocket190]

Oh we are certainly congenital idiots - perhaps that's why we think that paying dentists by tooth won't lead to lots of necessary fillings.

[100hp honda]

probly broke near the Y then the rest of the bike folded in half. wonder if he welded on the spars aswell ? maybe coil mount or something else. still i think the root of the problem started near the Y though. same scenario as the other broken bike. might sound stupid but exactly the reason im going to find out what alloy honda used and whether it needs to be re-treated . still aint made it to the metallurgist yet

[Gmbond]

This makes me wonder if the billet Y pieces are too stiff and instead of flexing like the thinner stock pieces it cracks or break above/below??

[AlisoBob]

This makes me wonder if the billet Y pieces are too stiff and instead of flexing like the thinner stock pieces it cracks or break above/below??

I've said this from day one.

[cmotodad]

Wasn't the broken frame we saw recently in the UK also? I would like to know if they came from the same shop?

[asteroid500]

any one got pics of the first UK squeeze....yeh and he didnt get hurt, what about pride....

i wonder if it was HEAT TREATED

[ukaf]

Wasn't the broken frame we saw recently in the UK also? I would like to know if they came from the same shop?

I know of four frames (in the UK) that've broken. Two of them broke on the Y piece welds and it was found before the bikes came apart - they vibrate really bad when it happens. Bear in mind that the UK is only 680 miles top to bottom so any news here gets around the whole dirt bike scene - especially bad news like this.

The bikes which snapped appear to have broken at the Y but continued to be ridden (maybe only for one jump). When the Y comes apart the stresses have to go somewhere and the spars are the obvious fulcrum point I'd thing. Standard Honda frames are known to sometimes develop cracks inside the spars right where the two broke so it seems it's the weakest point (on an um-modded bike). That said I've never seen an un-modded bike snap in half.

The two bikes which did snap used modified cradles and Y piece rather than Billet. It's most likely the failure was due to bad welding rather than the material used.

I have photos of the other bike - before and after it broke. Is it possible to put the photos directly in here or do I need to link to Photobucket (or similar). It'd be interesting to get some thoughts on why they failed.

Oh, the conversions were done (in all 4 cases I mentioned) by different people - as far as I know no-one in the UK will take the work on commercially as it's not worth the bother of researching it all for the small amount of work they'd get.

On dentistry - we're mostly a fairly practical lot over here. Teeth are for biting stuff so as long as that works we're happy not to pay dentists for the pain. Having a bad tooth pulled costs £20, having cosmetic work on it will be 10 times that (per tooth). By the way, what was that anesthetic thing someone mentioned earlier?

Here's a link to my Photobucket - the photos are on there.

http://s677.photobucket.com/home/ukaf_photos/index

I tried putting the photos here but they were huge, is it possible to post a clickable thumbnail?

[100hp honda]

were all the bikes crf250 ?

[ukaf]

were all the bikes crf250 ?

3 were for sure, the fourth might have been a CRF450.

Lots of people have used the CRF250 without any problems so I'd think that being the cause of the failures is unlikely. Maddison's SH bike is CRF250 based and it survives all he throws at it. Did you folks see this?

http://www.youtube.com/watch?v=_PvNRiz6zEw

[AlisoBob]

A 900' jump with a good landing puts far less strain on the bike than a 40' that you case hard.

[ukaf]

A 900' jump with a good landing puts far less strain on the bike than a 40' that you case hard.

Obviously. As a rule a pro rider will give a bike an easier time landing jumps because it'll be accurate. Kind of at odds with a lot of people's idea of "I'm just a play rider, I'll be fine even if the bike isn't quite right"

Maddison's Corinth Canal jump was anything but a good landing though and the CRF250 based chassis worked just fine.

[asteroid500]

thats why i put the cross brace back in my bike...i recon it helps take the harmonics out of the bike, were most remove it gain access to the barrell at rebuild time alitle easier...NOT ME though.
UKAF...i like you bash plate, i was contemplating doing this myself, after seeing yours i will be now.

[98cr500rider]

asteriod500, If you are referring to this bash plate in the picture link below, I think it would be a mistake to weld in a plate like this directly across the front engine bolt mounts. The frame needs to pull in a bit when you torque up this bolt and the bash plate will stress the frame and maybe start the crack that will ultimately cause the Y piece to fail.

However as you are doing a gen-1 frame, which has no Y piece, then carry on, but for gen-2 frames and onwards I think it’s a bad idea, better to weld on some lugs that you can bolt a bash plate onto.

http://s677.photobucket.com/albums/vv13 ... g&newest=1


.

[ukaf]

asteriod500, If you are referring to this bash plate in the picture link below, I think it would be a mistake to weld in a plate like this directly across the front engine bolt mounts. The frame needs to pull in a bit when you torque up this bolt and the bash plate will stress the frame and maybe start the crack that will ultimately cause the Y piece to fail.

However as you are doing a gen-1 frame, which has no Y piece, then carry on, but for gen-2 frames and onwards I think it’s a bad idea, better to weld on some lugs that you can bolt a bash plate onto.

http://s677.photobucket.com/albums/vv13 ... g&newest=1


.

None of the broken bikes are mine' they're just photos I gathered in a folder.

I agree with 98cr500rider. Adding strength to the rails will mean that the shared stressed are focussed elsewhere and I'd think that could be a bad thing. Bolt on plates work really well and the standard Gen 1 plate will probably fit - much easier than trying to fab. your own too.