built my own swingarm

[posplayr]

The truss structure is going to make the swing arm much stiffer than you would think

[Dave8338]

Having no idea how to fab anything and not building anything more complicated that Chef's wheel barrel frame...IF the welds hold and a good brace is added at the pivot point, that swing arm is just fine.

As far as the "drag race only" application, have you ever seen the torsional flex that drag machine (bike, car, or truck) goes through when the clutch is dumped? Ever sat in the seat and had "seat of the pants" experience of that force? Ever had to refab a "factory designed/built vehicle" for race applications because it was either too light or poorly designed when the hammer is thrown?

1/4" wall thickness over the 18"-24" swing arm that Nasty put together is OVERKILL to say the least. Because there will be little if any flex in the material that you used, the welds are the critical link here. Braced correctly, welded correctly, it would be the only part to survive a pile-up at any speed, and come out straight.

Nasty...I feel for you. It can be rough throwing "your work" out on a fourm. Those who know will offer good design suggestions and help where they can. Those who don't will criticize and slam you, for lack of real world experience and next to no fab knowledge. No one here has calculated all the factors that are going to apply to that particular swingarm and unless there is a full table of the #'s before those that are throwing stones and they can read the numbers and do the math...it is all speculation.

Make sure the welds have penetrated all the way through (a bevel on the materials to be joined works very well and two to three passes may be needed depending on the welder-wire-rod -flux and heat being used) and a good gusset brace at the pivot and ride it.

Start slow and use a laquer based primer (it will crack not flex if there is stress movement) over the welds instead of paint and watch them closely and you'll be fine.

[Nessism]

The truss structure is going to make the swing arm much stiffer than you would think

I seem to remember Ducati making some truss design steel swingarms, but the tubing diameter is roughly double what the guy used.

[errorcauser]

I've got a spare wheel barrel frame if you all want to build a swingarm.

LOL Is it heavy duty ?

Im not the sharpest tool in the shed, and i'll admit i just don't get all this. Why build your own swingarm ? Why not just get your hands on what was there to begin with and put it back ?

See ? I told you i don't get it.

[Hammered]

I seem to remember Ducati making some truss design steel swingarms, but the tubing diameter is roughly double what the guy used.

The purpose of using alloys like CM is to lighten the weight by be able to use a smaller dia and gauge material. Underbracing like the photo shows increases its ability to resist flexing to the point of failure by a larger amount. And the tubing used in stock swingarms is the stuff to be wary of. Youre looking at .080" NON Dom tubing. Its a medium grade of mild steel. In many cases, the backyard designer has roughly the same level of ability and access to higher grades of materials than the engineers that created the 1980 GS750. A quik Google will land you more useful information than was avilable 29 years ago.

[sschering]

OK Nobody has bothered to ask so I have to..

What welding process and equipment did you use to make the swinger?

[nastyjones]

Having no idea how to fab anything and not building anything more complicated that Chef's wheel barrel frame...IF the welds hold and a good brace is added at the pivot point, that swing arm is just fine.

As far as the "drag race only" application, have you ever seen the torsional flex that drag machine (bike, car, or truck) goes through when the clutch is dumped? Ever sat in the seat and had "seat of the pants" experience of that force? Ever had to refab a "factory designed/built vehicle" for race applications because it was either too light or poorly designed when the hammer is thrown?

1/4" wall thickness over the 18"-24" swing arm that Nasty put together is OVERKILL to say the least. Because there will be little if any flex in the material that you used, the welds are the critical link here. Braced correctly, welded correctly, it would be the only part to survive a pile-up at any speed, and come out straight.

Nasty...I feel for you. It can be rough throwing "your work" out on a fourm. Those who know will offer good design suggestions and help where they can. Those who don't will criticize and slam you, for lack of real world experience and next to no fab knowledge. No one here has calculated all the factors that are going to apply to that particular swingarm and unless there is a full table of the #'s before those that are throwing stones and they can read the numbers and do the math...it is all speculation.

Make sure the welds have penetrated all the way through (a bevel on the materials to be joined works very well and two to three passes may be needed depending on the welder-wire-rod -flux and heat being used) and a good gusset brace at the pivot and ride it.

Start slow and use a laquer based primer (it will crack not flex if there is stress movement) over the welds instead of paint and watch them closely and you'll be fine.

Thanks, Dave. A voice of encouragement is great. Thanks to all the others that encouraged me and those who offered opinions on how to make it better. Those of you who criticized my idea shame on you. Why did I build my own when I could just buy a gixxer one and make it fit. The answer is "because I can". I just wanted constructive criticism on what I have done.
I am hardly a novice at biking. Besides riding for 40 years, I have piloted my own 9 second gs1000 down the track dozens of times, although this is the first time I have built my own. This swingarm is not strictly for dragracing. It will primarily be for the street. I will brace it as recommended, I said that about 5 pages ago. I had it mig welded by a professional welder and will use the same guy to add a brace or braces. I will use every caution in the book when I test it out. When we drag raced I went over every inch of that bike after every pass and will do the same here with this bike.

nastyjones

[Jethro]

Every after market piece you can buy was homebrew, backyard tech at some point. Don't let the haters here get you down, just make sure your health coverage and death benefits are paid up!

[Hammered]

I want to see the finished project. Im a photo junkie and love seeing ideas other people have.

[tkent02]

Those of you who criticized my idea shame on you..... I just wanted constructive criticism on what I have done.

You ask for constructive criticism and when you get it, you start crying about it.
Did you want constructive criticism or did you just want a bunch of people sucking up to you?
Go back to kindergarten.

[salty_monk]

I wouldn't hesitate to make my own swingarm for personal use. I would use the same philosophy as 80GS1000.
Pick a stock design that would fit well with what you want & copy it. Remembering of course that your bike may be heavier than the one you are copying if relevant.

1/4" thick material is over the top, the size of tube is more important as stated but other than extra weight & making sure you get good weld penetration it won't do any harm.

You could take a look at the Yoshimura race design.

By the way you guys... who designs those 4" GSXR extensions? How do you know the engineering is sound? How do you know they don't place stress on the stock swingarm that it's not engineered to cope with?

Just playing devils advocate. As with a lot of this stuff I suspect someone took an educated guess, did it & tested it but certainly buying it off Ebay it would be good to be sure...

[Nessism]

By the way you guys... who designs those 4" GSXR extensions? How do you know the engineering is sound? How do you know they don't place stress on the stock swingarm that it's not engineered to cope with?

Just playing devils advocate. As with a lot of this stuff I suspect someone took an educated guess, did it & tested it but certainly buying off Ebay it would be good to be sure...

Thanks for saying this Dan, I was thinking the same thing. Another thing, aluminum is usually heat treated after welding; different alloys require different HT’ing techniques. Taking an existing Al part and tacking on extra pieces like these extensions anneals the metal in the heat affected zone and makes it weak. Most likely this reduction in strength is not a deal breaker though. Just trying to make a point to those advocating this method vs. building your own steel swingarm.

[nastyjones]

"You ask for constructive criticism and when you get it, you start crying about it.
Did you want constructive criticism or did you just want a bunch of people sucking up to you?
Go back to kindergarten".


Hey Pal,

To me, constructive criticism doesn't include phrases like
"would be ok for a 1;12 scale model, but for a real bike?????? f*&k that"
"You will die if you use that"
"6 months off work and a trashed bike".

Go back to kindergarten, you say. How about you stay out of this thread if you're going to be a jerk.

Nasty

[salty_monk]

Weren't all those non constructive comments by the same person or largely by the same person? Suggest you ignore said person & read the other posts.

I believe there is also a function where you can block posts from particular users should you not wish to read them. I'd forgotten about this function but I know it's working well for some members who don't wish to read the political threads.

Don't forget you'll have to lengthen your torque arm for the brake too. Suggest you put a secondary tube inside the first to strenthen it when you do or cut the ends off & weld them to a new longer tube.

Dan

[tkent02]

Go back to kindergarten, you say. How about you stay out of this thread if you're going to be a jerk.

Nasty

I'm sorry, I thought you were the jerk. People are trying to help you out and you sh:t on them.