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Discussion Starter · #1 ·
I am pulling what little hair I have in my head trying to build a subframe that suits the look I am going for. My issues are, I already paid a guy a good sum to f*ck up my first subframe design (as shown welded below). I now want to cut that entire frame off and build a removable plate style frame (the red scribble is what I want it to look like). However, I am unsure on material thickness and type.

Here is what I want to do>
1. have two 5-6" angle steel welded to the upper part of the frame for for use as mounts. The frame at that point is about 1" wide.
2. since I want to build a subframe similar in style to the last picture. It will be all aluminum flat plates, angles and rectangular bars for rigidity and support. (all bolted together, no welding...the guy below used 1/4" for the side rails)

My questions are:
How feasible is this design? I will be riding 1up only, I'm roughly 200 lbs.
My biggest concerns are what type of steel angle to weld to the steel frame? Hot Rolled, Alloy Steel? Is 3/16" too flimsy or should I go to 1/4" or 3/8"?
For the Aluminum plate - I have the following grade choices, I am thinking 1/4":
2024T3
3003H14
5052H32
6061T6
7075T6






Thanks!
 

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lb/hp is what it's about!
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First off what is fucked up with your subframe? It isnt a great pic to see details but it looks fine to me. :confused:

I dont like your subframe design. Not because it doesn't look good, it does, but I dont like that there will be a ton of force on those mounting bolts. You're basically sitting on the end of a 2' lever. Think of a 2' breaker bar vs a 8" wrench and how much easier it is to turn a stuck bolt with a breaker bar. You also need to keep in mind that while you may only weigh 200# you will momentarily weigh more then that when you hit bumps.

1. What does 5-6" angle mean? You have a piece of angle of unknown size and thickness that is 5-6" long welded somewhere on your bike in some unknown location and orientation?
2. I assume you mean 1/4" thick angle but thickness is only a small part of it. What are the other dimensions of the angle, how do you plan to fasten it to the other plates/bars/tubes/angles. You said bolts but how will you bolt together two pieces of angle when they meet at a 90*?

Why aluminum? Why not stick with steel? Steel would be a lot more forgiving.
 

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Discussion Starter · #3 ·
First, it's crooked as hell and I dont trust the welds. He threw on a shit load of bondo and covered it up before I got to inspect it. Second it isn't what I asked for, he went and did his own thing without consulting with me first.

Now as for the subframe; I understand that the longer the rails the more of a moment I am creating at the connection point...which is why I'm asking. Buckling of the subframe rail and shearing of the bolts are my main concerns. I obviously don't want to make the connection point too long(for aesthetic purposes) nor do I want to make it too small/flimsy.

The 5-6" is the length of the angle that I plan on welding along the the frame. Orientation is the inner part of the channel is open to the outside of the bike. The subframe would then bolt to that inside face to so mainly see the subframe and not the angle. As for material, I'm thinking 1" h x 2" v x ? thickness - which was my main question.

2. Partially answered above - the main angle I mentioned in the first post were the two pieces welded to the subframe, the other angle pieces are just for mounting the seat and underside of the subframe. The 1/4" was referring to the plate thickness which is used as the main subframe walls/rails.

And I figure aluminum would be easier to use with the limited tools I have but I could be very wrong. Below is a more accurate picture of what I want to do. Again, the main reason for me to do it this way is to save money by only making 2 welds. I'm in Ottawa, Canada and just got quoted 600$ locally for a guy to make me a custom sub and weld it to the frame. I think that is ubsurd.

 

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i'd think 1/4" for the angle would be sufficient. (i have to formal education on it tho). i don't know about the shear forces involved, but i'd use grade 8 hardware

with the 1/4" ally plate, lateral stiffness would be my next concern. the 2 main side plates would need bracing between them, and if you bolt braces on, be sure to use lots of loctite (i'd be using the red stuff)

the ally plates might look good with a bend or two, to give them some more shape.
 

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Discussion Starter · #5 ·
i'd think 1/4" for the angle would be sufficient. (i have to formal education on it tho). i don't know about the shear forces involved, but i'd use grade 8 hardware

with the 1/4" ally plate, lateral stiffness would be my next concern. the 2 main side plates would need bracing between them, and if you bolt braces on, be sure to use lots of loctite (i'd be using the red stuff)

the ally plates might look good with a bend or two, to give them some more shape.
Thanks, I'm going to reinforce the hell out of the subframe. That is the least of my worries. I think my design is fairly sound. What type of steel would make a good subframe plate? The local metal supplier only has 1/4" angle made from hot rolled steel, from what I understand its pretty ductile compared to other steel types.


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