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G-boxx2 project

wuchi

Chimp
Jun 7, 2008
17
0
Åre (sweden)
hey.
Some of you saw my first render of the frame in the Gearbox thread, well here's the final version for those who are interested.

Some helpful members at a swedish mtb-forum just gave me all the bearings and bolts for free.
Another member is going to watercut all the sheetmetalparts for the frame for a bottle of whiskey and the metal-warehouse is sponsoring with rawmaterial.

Me and a friend will lathe all the axles and the headtube.
We will also do the tube cutting/fitting at his place.

So now i'm only waiting for the sheetmetal and tubing to arrive at my place so i can send it to the watercut guy.

Finally the project is slowly on its way to become a frame.

I hope you like it!



ps. i will post updates along the way. as soon i have something to tell or show :)


Geometry:

Wheelbase: 1155mm
Chainstay: 430mm
Frontend: 725mm
BB-height: 350mm
Headtube-angle: 66°
Headtube-height: 120mm
Headtube-size: 1,5"
Axle-Crown-height: 570mm
Horizontal toptube length: 580mm
Seattube angle: 71,5°
Max seatpost insert: 220mm
Reartravel: 170mm
Rearshock: 8,75"x2,75"
Dropout: 150x12mm
Brakemount: IS-rear

Pics:





 
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buildyourown

Turbo Monkey
Feb 9, 2004
4,832
0
South Seattle
Nice work.
I think your disc side dropout is going to fold on you. I know you were trying to design everything to be waterjet cut, but without a center web, the brake mount will fold. I tried it once too. It didn't last one ride.
 

no skid marks

Monkey
Jan 15, 2006
2,511
29
ACT Australia
I've said it before, and I'll say it again.
If you moved the pivot to the Horst link position, you could customise your axle path.
Also by rotating the G-Box more vertical, you could raise your pivot(a tincy wincy bit)and make the front lower mount stronger, although I suppose you get more welding surface having it like that.
 

wuchi

Chimp
Jun 7, 2008
17
0
Åre (sweden)
buildyourown: The whole frame will be built in steel so the brake mount is not that weak as it looks, i've done some FEA on it and it seems to hold up well. the sheet-metal it's made from is 6,35mm (1/4") thick. well if it's break I'll just waterjet one with a center web. no problem :)

noskidmarks: a horstlink swing would generate chain growth, and I don't want to use a chaintensioner.
the only solution I think could work is the split-pivot with a eccentric axlemount for wheel and seatstay. but i don't want to interfere with patents and so on.
maybe the next version will have another solution at the dropouts.
 

ire

Turbo Monkey
Aug 6, 2007
6,196
4
the only solution I think could work is the split-pivot with a eccentric axlemount for wheel and seatstay. but i don't want to interfere with patents and so on.
Do you have intentions of producing the frame, or just building one for yourself? If you are building it for yourself then you don't need to worry, you get in trouble when you try sell products that infringe on a patent
 
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wuchi

Chimp
Jun 7, 2008
17
0
Åre (sweden)
I might sell a few frames in the future if someone's interested, but first I'll test the prototype for a season or two.

the next frame won't be in 4130. maybe some swedish steel called Sandvik NANOFLEX or Reynolds tubing.
If i can find some cheap russian titanium tubing and sheetmetal there will be an titanium version :)


I will also manufacture a floating brakeadapter for the frame to eliminate brakejack.
I'll post renders of that later
 

wuchi

Chimp
Jun 7, 2008
17
0
Åre (sweden)
a small update:

:: the sheetmetal is on it's way for watercutting, i expect to have it at my place in a few days.
:: the bearings and bolts have arrived.
:: I just found out that the new place i'm working for just got their 5-axis CNC-mill. (perfect timing) :)
:: My friends father works at a custom paint-shop and will paint my frame for a small cost.

I feel so lucky right now :)
 

ohio

The Fresno Kid
Nov 26, 2001
6,649
23
SF, CA
Really nice work. Looks great and if those brake mounts/drops are steel, my gut check says they're sufficient.

One tweak i would make is to go with a standard 1 1/8" headtube. On a steel frame the 1.5" is completely unnecessary (unless you are running a 1.5 single-crown) and reduces the weld surface for your top and down tube, compromising critical strength. I would be realy worried about that headtube junction on a DH bike as it is currently designed.
 

EVRAC

Monkey
Jun 21, 2004
757
19
Port Coquitlam, B.C., Canada
Awesome work. I can't wait to see it built.

I agree with not having a tensioner. It's one of the main points of the whole thing.

Too bad it's so tricky to have a split pivot where you can adjust chain length, because then you wouldn't need the floating brake.

One more thing: Carbon Drive belt instead of the chain.
 

HaveFaith

Monkey
Mar 11, 2006
338
0
buildyourown: The whole frame will be built in steel so the brake mount is not that weak as it looks, i've done some FEA on it and it seems to hold up well. the sheet-metal it's made from is 6,35mm (1/4") thick. well if it's break I'll just waterjet one with a center web. no problem :)

noskidmarks: a horstlink swing would generate chain growth, and I don't want to use a chaintensioner.
the only solution I think could work is the split-pivot with a eccentric axlemount for wheel and seatstay. but i don't want to interfere with patents and so on.
maybe the next version will have another solution at the dropouts.
Check out my gboxx bike build thread about the brake mounts. I had 4130 dropouts at 5/16" thick with a very similar webbed design and they did end up folding inwards towards the wheel. Both frames that we have built now have a full 1/8 plate welded to the back side, so now its like a pocketed section. Haven't had any stiffness issues since.

Otherwise, the design looks really clean, simple and efficient. Nice inclusion of the adjustable dropouts. Can't wait to see it come together!
 
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wuchi

Chimp
Jun 7, 2008
17
0
Åre (sweden)
The brakemount won't be a problem, It's waaay stronger than the balfa bb7 brakemount and I never had any problems with that. I did some changes after the renders were posted.

About the headtube I haven't really decided yet, I'd like to mount a fox 36vanRC2 with a 1,5" steerer but as I'm going to manufacture the headtube myself I can always change my mind until its welded on the frame. The only reason I would change the headtube-size is for the weight. Probably a 1,1/8 fork would work just fine for me, i'll decide later :)

And yes it will have belt drive, but I will buy both kits and try what I like the most.

the next frame might as well have some kind of split-pivot, I've started to sketch on a system that has an eccentric axlemount for chaintension. hope DW doesn't mind :)
 
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unskilled

Monkey
Jul 12, 2007
218
0
there need to be more of these bikes.
looks exactly like a transition blindside/or bottlerocket frame
with sick drop outs
 

jonKranked

Detective Dookie
Nov 10, 2005
85,559
24,182
media blackout
there need to be more of these bikes.
looks exactly like a transition blindside/or bottlerocket frame
with sick drop outs
but its cooler than either with a g-boxx

Wuchi - very cool design! I look forward to seeing it completed.

I do agree with what some folks have already said - you are going to want to beef up your rear dropouts. My advice - since they are bolt on (and can be easily replaced) design a few other dropouts styles, each getting a little more beefed up so to speak. Get them all cut at the same time (since you are doing water jet, if you have the spare material that is), so if one set breaks, you will have something else to install right away. This will also help you figure out how strong they need to be.
 

wuchi

Chimp
Jun 7, 2008
17
0
Åre (sweden)
jonKranked: i've ordered all the sheetmetal parts so i have for two extra frames, just for that reason, if i screw one up during tubefitting or welding. And this is i only a prototype, it wont last forever. I want to build a lighter version later in another material later.

IH8Rice: yes, the frame have been redesigned a lot of times, first I wanted to build a more DH race inspired frame, lower BB, more reartravel and shockstroke than this current version.
But now it seems like I'm going to move away from the mountains for some smaller hills around the capital of Sweden; Stockholm, so the bike was made a little "smaller".
More like the SX-trail I had before.

It won't have DH-components but more freeride-inspired parts that still can handle the dh-stuff pretty well.