Broken AF frame - Do you know of any?

[mxaniac]

That would be correct, it is.  I'm simulating a high load on the steering head such as when you overshoot the tabletop and land on the front wheel, not that I would ever do that but you know hypothetically.

Here is a deformation plot, in this model I've boxed in the high stress area with 5 mm plate.

[sandblaster]

Very nice.
I guess it's time to up the tube thickness...

[mxaniac]

Just to be clear, that last plot is showing exaggerated displacement and not stress.

[jBernard]

wonder if putting a strip of alum the width of the rail on the inside of the rails between the Y and the top motor mount to beef it up would help. basically just re-inforce the area showing failure.
i'm doing a front headstay as we speak, glad to see that it may take some of the load off.

[mxaniac]

Well for entertainment purposes mind you I modelled up fish plates between the rails and on the side of the rails towards the engine tiening the Y together with the motor mounts and it greatly reduced the stress in that area.  Combined with the front head stay and a rigid rear one things are starting to look iffy instead of disasterous.

[sandblaster]

Cool!
But we need pics 

[sandblaster]

Can you get your engine in and out?  With all the cases on?  If i recall correctly the water pump is always part of the problem getting it out.

Yes  
Remove the fuel tank, carb, rad hoses, chain, the rear head stay, mounts bolts, exhaust, ect.... Push, pull, twist, shake it a bit, then start over, do this 2-3 times and out it comes... piece of cake.

[Ims Roll]

Can you get your engine in and out?  With all the cases on?  If i recall correctly the water pump is always part of the problem getting it out.

Yes  
Remove the fuel tank, carb, rad hoses, chain, the rear head stay, mounts bolts, exhaust, ect.... Push, pull, twist, shake it a bit, then start over, do this 2-3 times and out it comes... piece of cake.

sounds a little easier then how the motor comes out of my beta lol....

[mxaniac]

I went with this for the front stay:



Very tight.

[sandblaster]

I like it.

[nikabele]

I've heard about people heat treating or stress relieving, but my question is, what every bodies opinion on doing the frame rail mounts along the bottom with the two top mount front and back. I am done with my frame I have both front and back top mounts and am deciding if I need to heat treat it. With the front top Mount you are basically making the motor part of the frame, not allowing the weight and pivot of the motor itself directed towards the fabricated y yoke. Hope I am not asking a repetitive question. What does everybody think?

[jBernard]

i'll say this....
service honda doesnt heat treat
and i just found out lately that their whole rail design is 2pc SOLID machined pieces. not bent tubing.

the VAST majority of the distributed weight is on the swingarm pivot and the top engine mount on the frame rails (below yoke).

[Starky307]

Has anyone considered that by moving the "y" section up we have actually exposed the frame rails to a high stress point?
The point most of these breakages is occurring is in an area that the standard 250f or 450f would have the main large spar still in place.

With my build I put a lot of effort into the rear head stay to ensure it was positioned to provide the best load sharing opportunity possible.
I am a firm believer that those that use a 09 or later frame need to mount the rear head stay from the spar not from the side.
Don't forget that the 09 onwards 4 strokes share the load of the top of the motor across the rear and front of the head so the strength isn't required in the rear so much.

That's my $0.02

I hope my theory is right as I'm about to start riding my build in the coming weeks, I will be monitoring the frame each ride.