How to ruin a perfectly good stock frame

[mlc216]

As I said, it doesn't take a rocket scientist to figure out when something is poorly constructed. Any serious frame modifications need a proper jig to ensure everything is in line, and I see nothing worth calling a jig anywhere near that bike.

A frame built with a jig is only as straight as the jig. I'm building ONE frame, and a jig is NOT needed to build a frame straight. A level, tape, and plum bob are plenty enough to build anything you want straight. Even the best jig cannot hold a frame perfectly straight if it's not welded in an manner that promotes even heating. When welds are thought out and planned appropriately, a fabricator can pull metal one way or another as desired. Basically I used the frame as a jig. I braced around areas I wanted to stay put and cut and extended other areas using the existing triangle to create the geometry I wanted.

Then let me tell you this: Nothing in the pictures posted is over-engineered. I can't even spot a properly notched tube (which is basic frame building 101) and then it's been roughly MIG-welded together and had it's welds ground down. If you want to extend or change the bend of a tube midway you need to make slip joints and stuff which gives the tube strength where the weld is. There's nothing of that here.

To me, it seems like this was thrown together on a hot afternoon using an angle grinder.

I don't have a "tubing notcher", but I do know how to properly notch or cope tubing. All of my tubing was test fit multiple times to assure proper fitment before it was welded. The only place I needed to extend or change the bend of tubes was on the lower frame rail connections front and rear. I created a slip joint up front and lugged, plug welded, beveled the tubing, and then did a full penetration weld on the rear joints. Both of these connections are strong, but I will add a triangular gusset on the front joints and add some extra bracing on the inside of the frame rails on the rear connections.

I took my time because I enjoy metalwork and I want a strong frame. This was not just thrown together... maybe my crappy cell phone pictures have given the wrong impression.

[mlc216]

Honestly re-read this from the beginning. Nessism was quite polite in his suggestion that more bracing would be needed. The OP then went off talking about how he would remove his trash from the board and even in a slant at Nessism's stable just for good measure. When you come in with an attitude that everyone is against you, people are going to end up against you.

I apologize for coming in with a negative attitude. I shouldn't have responded how I did originally. I will continue to post progress and answer as many questions as I can, and I'll do it without any negativity.

[Krunk_Kracker]

I have no idea from a structural point whether or not his frame is good.

I'm just commenting on the trend that anything done that isn't OEM is usually poo-poo'ed on this forum.

[Nessism]

The frame is not done... it will get a seatpost and a few gussets.

The neck to frame attachment alone is good for over 35,000 lbs in shear. For a 300 lb bike with a 200 lb rider that seems to be plenty strong. If I can find some freetime this week I'll draw it up in 3D and do a little FEA for you so you guys can sleep at night.

Shear strength is one thing, but there are other important design considerations for a motorcycle frame too, such as torsional and lateral rigidity of the front end so the frame is not unstable at speed when upset by road inputs. I suggest you run some moment of inertia calculations on the torsional and lateral stiffness of your design, particularly the front end, and compare to a stock 450 frame as a reference. This frame is clearly designed to flex in a vertical plane, which may be okay for a ridged frame, but a torsionally flexy front end with make the bike prone to possible tank slappers.

[mlc216]

it's been roughly MIG-welded together and had it's welds ground down...

Also, I've not ground down any welds...

[Adler]

http://www.youtube.com/watch?v=5DmYLrxR0Y8

[Nessism]

I'm just commenting on the trend that anything done that isn't OEM is usually poo-poo'ed on this forum.

My beef with so called "customs" is the fact that the huge majority of them wind up with straight pipes, or something similar. Why?

[mlc216]

Shear strength is one thing, but there are other important design considerations for a motorcycle frame too, such as torsional and lateral rigidity of the front end so the frame is not unstable at speed when upset by road inputs. I suggest you run some moment of inertia calculations on the torsional and lateral stiffness of your design, particularly the front end, and compare to a stock 450 frame as a reference. This frame is clearly designed to flex in a vertical plane, which may be okay for a ridged frame, but a torsionally flexy front end with make the bike prone to possible tank slappers.

With more rake comes more stability at speed as long as the rake/trail calculations are correct. I'll check into the torsional and lateral stiffness as well, but as I said before the bike will not, and was never meant to handle like a sport bike. It will handle much more like a cruiser with most of the weight residing over the back wheel which removes a lot of force from the front end especially in cornering. Yes, this removes a certain amount of traction from the front end, but again it's not a sportbike.

[mlc216]

http://www.youtube.com/watch?v=5DmYLrxR0Y8

haha

[afholderman]

http://www.youtube.com/watch?v=5DmYLrxR0Y8

Haha, that's perfect.

[Agemax]

keep up the good work mlc216 and keep them pics coming in.
ignore the boring farts that are only interested in concourse restoration projects, they have no imagination

[mlc216]

Ha well I don't want anymore drama. I appreciate the concern, but let me finish it up and we can discuss what areas may need more support then.

[old_chopper]

Hey what's the matter with straight pipes!?! My 550 has them, well with an internal restrictor. It's disappointingly quiet! Guess the small cc's have a lot to do with that.

[tkent02]

The frame is not done... it will get a seatpost and a few gussets.

That's a start, a seatpost would help immensely.

[mlc216]

That's a start, a seatpost would help immensely.

Yeah I have to go get the other motor from my old house... Want to mock it up so it's not impossible to get the motor in and out.