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My idea for a gearbox bike

EVRAC

EVRAC

Monkey
Jun 21, 2004
757
19
Port Coquitlam, B.C., Canada
8 inch travel. Shock is 240 x 76. Leverage ratio from 2.8 to 2.5
Single pivot.
Double downtube and seattube-braces for a partial space-frame.

What do you think? I'd like some feedback before I start serious solidworks modeling.
 
MobileChernobyl

MobileChernobyl

Monkey
Apr 16, 2006
392
0
Golden, CO
if you can get the solidworks 3d file of a g-boxx, that frame could be rough drafted up in like 6 hours tops haha - granted you've already done the calculations for obvious interference, bearings, tubing, etc. I don't know if your trying to keep it overly simple or not, but you could throw a linkage in there and maybe lighten it, and lower the cog, not to mention modify your leverage rate and get rid of the #1 response your gonna hear from most people "OMGZORS your shock is gonna get bombarded with exploding ROX!!!" or something like that. This comment holds true especially since your going twin-spar for the downtube, unless you'll do the obvious thing and place some kinda carbon fiber glory-hole-esk gaurd there.

Make a rough draft 3d model and post it, more people will comment cause they can better relate to it.

Oh yea forgot...

LOOKS FLEXY

DOES IT COME IN ROOTBEER/CREAM SODA??
 
EVRAC

EVRAC

Monkey
Jun 21, 2004
757
19
Port Coquitlam, B.C., Canada
MobileChernobyl said:
if you can get the solidworks 3d file of a g-boxx, that frame could be rough drafted up in like 6 hours tops haha - granted you've already done the calculations for obvious interference, bearings, tubing, etc. I don't know if your trying to keep it overly simple or not, but you could throw a linkage in there and maybe lighten it, and lower the cog, not to mention modify your leverage rate and get rid of the #1 response your gonna hear from most people "OMGZORS your shock is gonna get bombarded with exploding ROX!!!" or something like that. This comment holds true especially since your going twin-spar for the downtube, unless you'll do the obvious thing and place some kinda carbon fiber glory-hole-esk gaurd there.

Make a rough draft 3d model and post it, more people will comment cause they can better relate to it.

Oh yea forgot...

LOOKS FLEXY

DOES IT COME IN ROOTBEER/CREAM SODA??
Click to expand...
Thanks for replying. 184 views and only one reply.
I've got the gboxx model and the assembly is well underway. The cog is in it's proper place for the gboxx. Please tell me the advantage of adding a linkage? I thought the leverage curve looked quite good.

And yes, of course there will be a shock guard.

Comments please??
 
noskcaj

noskcaj

Monkey
Oct 24, 2005
106
0
Northford, CT
What type of material are you thinking about making it out of? The weight placement looks good, good pivot point, good braking/pedaling tendencies. The only thing I can think of that might be a problem is the weight of the double tube/space frame front section, but that all depends on material. Would it be possible to somehow make it from carbon if you have the facilities and do more of a shell with the gearbox inside and room for the shock/swingarm?
 
buildyourown

buildyourown

Turbo Monkey
Feb 9, 2004
4,832
0
South Seattle
Building a bike with a double down tube will be tough. Finding tubes that will be strong enough without being overly heavy is going to be a challenge.
The main advantage of a link is the ability to move the shock placement. You obviously have a shock rate curve in mind and this theory dictates the relationship between the swing arm and the shock. Hence your shock running into your DT. By using a dogbone and a swinglink, you can place the shock and link somewhere in the frame that is convenient, and then use the dogbone to attach the swingarm. If you don't/can't machine one, just steal one from a Turner or other similar bike and design around it.
 
xy9ine

xy9ine

Turbo Monkey
Mar 22, 2004
2,940
353
vancouver eastside
looks neat. love seeing the independent builders / backyard tinkerers leading the gearbox revolution. vaguely reminds me of an old se quadangle. i personally tend to prefer rising rate link bikes, but that does introduce more complexity. so, how does one actually go about buying a gboxx? i'd assume they're oem only & not available to the public.

flashback:

 
jonKranked

jonKranked

Detective Dookie
Nov 10, 2005
85,871
24,456
media blackout
If you have access to solidworks, then you can probably design a lower carriage and get it machined if you are working with Al. Oh and if you have some friends at a machine shop. You might have to pull some strings with them.
 
SPINTECK

SPINTECK

Turbo Monkey
Oct 16, 2005
1,370
0
abc
That looks unbelievably sweet. Your design puts the majority of weight LOW and CENTERED!!

This is above many people, including me. BUt it looks sweet and I'd ride it.
 
EVRAC

EVRAC

Monkey
Jun 21, 2004
757
19
Port Coquitlam, B.C., Canada
jonKranked said:
If you have access to solidworks, then you can probably design a lower carriage and get it machined if you are working with Al. Oh and if you have some friends at a machine shop. You might have to pull some strings with them.
Click to expand...
There would be many machined al. parts. I've been in the business of CNC machining for 12+ years, so I've got more than a few connections.
 
EVRAC

EVRAC

Monkey
Jun 21, 2004
757
19
Port Coquitlam, B.C., Canada
xy9ine said:
looks neat. love seeing the independent builders / backyard tinkerers leading the gearbox revolution. vaguely reminds me of an old se quadangle. i personally tend to prefer rising rate link bikes, but that does introduce more complexity. so, how does one actually go about buying a gboxx? i'd assume they're oem only & not available to the public.

flashback:

Click to expand...

That frame is rad! Lots of double tube frames out there: Nicolai, Evil, etc. The Milliard racing bike had double top and downtubes, with diagonal reinforcements all the way, and it was still light. I was also considering the idea shown there of having the downtubes meet the top of the headtube and the toptube to the bottom of the headtube. Sort of makes sense with the way the loads are applied.

What would you consider an ideal rate curve? I was thinking, very slight rising rate, because the shocks themselves nowadays also have their own progressivity.

Buying the g-boxx? You are right, it's oem only, so I was assuming I would just say I was a builder? I guess there might be minimum qtys. The other thread with the "sub-40 lb g-boxx", the author was able to order one direct.
 
R

Rover Nick

Monkey
Oct 17, 2006
280
0
xy9ine said:
so, how does one actually go about buying a gboxx? i'd assume they're oem only & not available to the public.
Click to expand...
You'd probably have to get in touch with Karl Nicolai, I'm sure he'd be more than happy to work with you and work something out.
 
L

LMC

Monkey
Dec 10, 2006
683
1
EVRAC said:
Thanks for replying. 184 views and only one reply.
I've got the gboxx model and the assembly is well underway. The cog is in it's proper place for the gboxx. Please tell me the advantage of adding a linkage? I thought the leverage curve looked quite good.

And yes, of course there will be a shock guard.

Comments please??
Click to expand...
looks decent to me also, that change in rate is about the most progressive you can get with a single pivot. i wouldnt bother with a linkage myself.

if you want to make it more progressive you could just get a progressively wound (variable pitch) spring made up to fit your shock, which would probably cost about the same as getting all the linkage parts machined up... and weigh less.

as for obtaining a g-boxx, best way would be to say you are a builder and perhaps set up a website holding page and contact him using a proper email account from that website, i doubt youd get much luck with a hotmail or some other such account. A sample aint cheap tho. about the same price as a rohloff speedhub..

if i were to design around the g-boxx standard id make the pivot a little higher and run a chain up to the pivot. it may add a little weight with the extra axle etc but would provide a better suspension action at the rear in my opinion, it would also mean no need to pierce the downtube with your shock as the whole swingarm assembly would be higher

also it would give scope for manipulating the size of the cogs to provide a better anti squat
curve to the rear wheel.

you could also mount an onboard brake too.

Carve has to be the coolest name ever for a bike company!!
 
H

HaveFaith

Monkey
Mar 11, 2006
338
0
The bike looks good, especially from a concept perception. One thing that I would recommend, especially with going with the split downtube is to keep it as simple as possible. Think about where the forces are coming from and their direction and try to handle them in the most efficient way. With the weight of a gearbox, its very easy to overbuild and end up with a 48lb bike. I like the look and think you should get that 3d model going!
 
no skid marks

no skid marks

Monkey
Jan 15, 2006
2,511
29
ACT Australia
You also have to concider the weight of the gearbox and the stress it can cause on the frame in a crash(cassing a big jump,frame stops,gearbox eight wants to keep moving).
 
buckoW

buckoW

Turbo Monkey
Mar 1, 2007
3,786
4,727
Champery, Switzerland
Looks cool! The one thing I would say is that the chainstays look very long. 450mm to 470mm at full travel seems a bit much to me.....but I like the steep and tech trails on short and slack bikes.
 
H

Hougham

Monkey
Mar 28, 2007
375
3
EVRAC said:
8 inch travel. Shock is 240 x 76. Leverage ratio from 2.8 to 2.5
Single pivot.
Double downtube and seattube-braces for a partial space-frame.

What do you think? I'd like some feedback before I start serious solidworks modeling.
Click to expand...
It should work fine. The swing arm would have to be quite weighty due to the design but that’s not the end of the world. The hard bit would be taking that geometry drawing a step further and designing a full frame out of it. The its the fun bit, you get to make it :)
 
NY_Star

NY_Star

Turbo Monkey
Jun 10, 2007
1,046
0
10 Sq Mi Surrounded by well armed white men
This looks live a very good idea. I would not mess with a linkage on this bike. If you build this one and want to move on to something else then you may want to mess with a link. You may be able to call Sully from Rotec. I know that he has been building a Gboxx bike. He may be able to sell you one
 
vitox

vitox

Turbo Monkey
Sep 23, 2001
2,936
1
Santiago du Chili
hey i like it a lot, creative with the shock arrangement !

one thing i remember from pedalling around on a gearbox bike was that it bobbed a lot, more than the bb7, and looking at the rendering it says 0,1mm chaingrowth, maybe you could put a slider in there to tighten up things?
 
EVRAC

EVRAC

Monkey
Jun 21, 2004
757
19
Port Coquitlam, B.C., Canada
vitox said:
hey i like it a lot, creative with the shock arrangement !

one thing i remember from pedalling around on a gearbox bike was that it bobbed a lot, more than the bb7, and looking at the rendering it says 0,1mm chaingrowth, maybe you could put a slider in there to tighten up things?
Click to expand...
If, by slider, you mean sliding dropouts, then yes it will have them. The small chaingrowth shown is because there was no way to accurately snap the "idler sprocket" to the main pivot, so it's out a tiny bit. In real life there would be no chaingrowth.
 
P.T.W

P.T.W

Monkey
May 6, 2007
599
0
christchurch nz
Nice work!:rockout:I like the simple unclutered layout.think your heading in the right direction.
Have you thought of rotating the lever arm for the shock clockwise an locating the bottom of the shock to the bottom g-box "bulkhead"?This area is all ready a strong area of the frame an if you use it for a shock mount itll save weight from not having to beef up another area...an also lower the c of g even more.
Also im not to sure of a double down tube idea.IMO a single tube would overall be stiffer an weigh less,the triangle it formed would be self bracing esp if you add a few webs ala Milliyard.
An unbraced square section can still lozenge where a triangle is self bracing
 
L

LMC

Monkey
Dec 10, 2006
683
1
im not too sure about the double down tube either but if you do want to have this feature id say this would be the best arrangement..

kinda like a cooler looking millyard...
 

Attachments

L

LMC

Monkey
Dec 10, 2006
683
1
EVRAC said:
Yeah, those bikes look rad. Always loved the lines.
By "best arrangement" do you mean having a plate across the bottom of the two tubes?
Click to expand...
yeah they look pretty cool!

i wasnt thinking too much of the plate, more the layout of all the tubes in the front triangle.
i just think that layout would chanel all the stress from the g-boxx most efficiently, and would result in a very stiff, strong front triangle. The whole G-boxx mount/ shock mount could be machined in one piece then you are looking at possiby the lowest CoG out of all the G-boxx bikes.

it would be harder to build than your layout though..

have you considered using carbon fibre for any of the project? with you being a machinist the moulds wouldnt be too much of an obstacle.
 
H

HaveFaith

Monkey
Mar 11, 2006
338
0
unskilled said:
:banghead: reading this thread made me go out and convert a transition dirtbag into a gboxx bike via illustrator, good homework distraction.
Click to expand...
Nice drawing. Looks pretty similar to the frame I am currently building. Execution and pivot placement are fairly similar, but they definitely resemble each other.
 
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