[TrueScotsman]

OK fellow Monkeys;
Some of you may know from other threads that I have been posting in that I am currently building my own G-boxx DH Bike. Well, I am just back from the Waterjetters and I can't shut up about it anymore! So, I am starting my own thread (a bit like Havefaith did) following the progress of the frame.

A wee bit about the frame design;
It is based around the G-boxx2 gearbox.
It has a Split-Pivot rear end.
I am testing an Anti-Squat idler system.
Rocker Link to give a slighty progressive rear wheel rate.

I don't want to show my CAD drawings of the frame just yet (don't want to give everything away at once!) but here are a few small pics of stuff so far(some of the waterjet stuff has still to be milled out);

What d'ya reckon?

P.S.- It won't be flexy, will not come in Rootbeer, and won't need moar shimz!

 

[BadDNA]

When will I be able to get one?

Sounds like a fun project, I wish I had the time and resources for something like that.

 

[al-irl]

looks cool can't wait to see more

 

[monkeyfcuker]

Subscribed!

Awesome dude, gonna love watching this thing come together and can't wait to see it on the trails!

How's that Fort William deadline looking?

 

[TrueScotsman]

How's that Fort William deadline looking?

Hmmm, VERY tight!

 

[Vrock]

I designed a G-Boxx bike last year, I used a Horst link in the rear, but It doesn't need a tensioner. Then I heard that G-Boxx 3 was comming so I'm waiting until I know how it is...

 

[TrueScotsman]

Yeah I know about the g-boxx3 but I bought the G-boxx2 last year. I didn't get my arse into gear quick enough then (spent a year just looking/fondling it!) but nevermind!

 

[FCLinder]

In no way am I trying to open a can of worms, just fair warning to you,

Be ready for DW to say something about you using the Split Pivot on your design. Not to throw him under the bus our anything, because I do feel he has helped bike designs out a lot over the years. I just remember when I posted up a design I worked on for a long time early last year that looks much like the now new Devinci Wilson and got a personal E-Mail (2 hours later) from DW saying it looked much like his design. Didn’t know how to take that one. Now with that being said I do have respect for him and at the time only planed to make the frame for me only and not to sell. Now with the new Wilson being made for 2011 I have no need to build my own design. It’s already done and I don’t have to do any more work on it.

Still think it would be super fun to make your own frame. I will some day. Glad to see more people doing it. Good luck with the build!!!!!

Cecil

 

[Prettym1k3]

Epicthread will be epic.

 

[TrueScotsman]

Be ready for DW to say something about you using the Split Pivot on your design.

It's cool, I already have asked DW and said it was only for my own one-off and he said it was OK. This is not for re-sale, just for laughs.

 

[Trekrules]

Intressting project,im gonna follow this thread.Can't wait how the complete bike looks like

 

[FCLinder]

It's cool, I already have asked DW and said it was only for my own one-off and he said it was OK. This is not for re-sale, just for "$#!+s and giggles!"

Good, glad he is cool with you doing that. Props to him for working with you.

Cecil

 

[Total Heckler]

Get building dude! Lets see some more!

 

[no skid marks]

If your running an idler, why not use a Horst link, and get more rearward axlepath?
Will you be getting more meat milled out of those parts?
G-Box 3 will have same mounts anyway, won't it?
Nice job, I look forward to watching it evolve. But please, post all the info you got, feedbacks what your after afterall isn't it?
What geo will it have? DH or more trailbike?

 

[TrueScotsman]

If your running an idler, why not use a Horst link, and get more rearward axlepath? Hopefully things will become clearer in time.

Will you be getting more meat milled out of those parts? Yeah, most of the parts will be hand milled down- only the profiles were done in waterjet as it is only a 2D process.

G-Box 3 will have same mounts anyway, won't it? I was told that G-boxx3 won't conform to the g-con standard in an e-mail from Kalle Nicolai.

Nice job, I look forward to watching it evolve. But please, post all the info you got, feedbacks what your after afterall isn't it?

What geo will it have? DH or more trailbike?Full-on DH geometry. Long and low-I'm 6'3" so it has a really long toptube and i've gone full-on with a 13.5" BB as the g-boxx has more clearance than a std chainring. We'll see if this is a mistake and is too low!

Reply above

 

[karpi]

this sounds promising! Damit, I need to get out of school, get a job, and start building my own ****!

 

[Bikael Molton]

good stuff; looking forward to the finished bike.

 

[IH8Rice]

is there any downside to using a waterjet to cut your pieces?

 

[ocelot]

is there any downside to using a waterjet to cut your pieces?

From the parts i've seen for my school's formula sae car, you get a pretty rough surface from waterjet cutting. I'm not sure if it's possible to get a smoother surface, but I guess it would be more costly/time consuming

 

[IH8Rice]

I'm not sure if it's possible to get a smoother surface, but I guess it would be more costly/time consuming

actually, he did say he was going to hand mill them down so more, so that should fix that.

 

[TrueScotsman]

Yeah, going to hand mill/ream down the critical dimensions. Waterjet is only accurate to 0.1mm so any crucial holes,etc are undersized and will be turned/reamed further. Waterjet was good for removing large areas of alu and cutting complex shapes.

 

[istratetm]

do you have the heat treatment process sorted? what aluminium do you use? best of luck

 

[Vrock]

That hole is there for some reason...

 

[TrueScotsman]

That hole is there for some reason...

Ha ha!-someone has been studying the pics!- Unfortunately that is the NON-driveside g-boxx mount. The driveside mount is not shown (that would give too much away!)
The only reason for that hole is that it lines up with a torx bolt on the g-boxx2 so it is for access only in case it ever came loose. Sorry to burst your bubble!

As for heat-treating the Alumin(i)um is 7005 (from fairing.com) and requires only artificial aging not sloution heat treatment- easier for a one-off frame for me.

 

[FlyinPolack]

That's really cool, I can't wait to see it built up!

Waterjetters are the best thing since sliced bread!

 

[Vrock]

Jejeje, I think I can almost see what are you going to do. An Idler close to main Pivot with the chain under or over it. I think It can work with the Chain under the Idler if the Idler is very close to the main pivot. Do the math and you'll see, It's only a Gear combo so It's not a lot of work. You are probably going to Archive the same thing that Nicolai did with the Horst link..

 

[fluider]

Heeeey man!! This is great Definitely post further pictures and overall progress. It's very encouraging. Those parts look quite massive but safe!, have you estimated the overall weight already? Is that headtube for 1.5" dimension? There are already some interesting comments in here, aren't they ?

 

[HaveFaith]

Awesome to see you are getting going on it! It will be a fun process. FWIW, I definitely recommend shot-peening after you weld her up. The fairing stuff could be sitting on the shelf for a long time, artificially aging before weld and you may get some interest HAZ effects. I like the idler idea, its something I have been thinking about adding the the rear-end of my bike for fun.

As for waterjetting before machining, there can be a few effects:
1) Sometimes it is harder for the machinist to fixture the part to cut if it is already near-net shape. This is mostly machinist preference, but will probably come up in manufacturing discussions.
2) The rough texture the waterjet produces does not play well with fatigue and aluminum. Make sure to clean up any high stress surfaces or edges with either machining or polishing (or just Shot Peen the thing!)
3) You are right about tolerances, just another thing to consider

Have fun, keep up the work!

Ha ha!-someone has been studying the pics!- Unfortunately that is the NON-driveside g-boxx mount. The driveside mount is not shown (that would give too much away!)
The only reason for that hole is that it lines up with a torx bolt on the g-boxx2 so it is for access only in case it ever came loose. Sorry to burst your bubble!

As for heat-treating the Alumin(i)um is 7005 (from fairing.com) and requires only artificial aging not sloution heat treatment- easier for a one-off frame for me.

 

[TrueScotsman]

Hey guys cheers for all the encouragement! To answer some questions;

Yes it is a 1.5" headtube (allows for angled/offset spacers to fine tune head angle,etc)

As for weight and the fact that the parts look massive- Remember that there is a LOT of meat still to be milled off-i.e. the g-boxx mounts need to be 10mm thick but I could only source 25mm thick 7005 Alu!!! I don't have an estimated weight yet-I am still errring on the safe side so I don't expect to break any low-weight records.

As for further progress, tonight me and my Dad (my hero!) turned down some seatstay bearing housings.-see pics;

Before;

During with my Dad;

After;

Keep the questions coming!

 

[TrueScotsman]

Cheers Havefaith- I will definately look into shot-peening. I appreciate that you have a lot of first-hand knowledge of these things. BTW how's the latest frame/electronic shifter coming?

 

[Tetreault]

unreal i can't wait to see the final result. do you have a eta as to when you would like it to be all done for?

 

[istratetm]

regarding the heat treatment. an alternative to it is to delay the cooling of the welded area as long as possible. this way u don't aloud for big irregular grain to form. big grain structure causes big gaps between molecules causing early fatigue and cracks(breakes).
the solution is to have a pre heated sandbox in wich to put the frame after welding, and let it there for up to 4-8 hours. the sand temperature should be around 150 degrees Celsius.
this might be a solution that i learned at University, for one off products that complex heat treatment is not the best option(cost related).
best of luck with the fabrication and cheers to your dad!

 

[trib]

More pics!

 

[essenmeinstuff]

Good, glad he is cool with you doing that. Props to him for working with you.

Cecil

FWIW, patents can be used for personal use by anyone.

To the OP, sweet project!!

 

[ChrisKring]

FWIW, patents can be used for personal use by anyone.

To the OP, sweet project!!

caution on this. The above statement is mostly correct in the EU. US law is much more strict. Even for personal use.

In the case of the EU, I would think the definition of personal use could be debated if such use included use by a professional racer. Consult an attorney for a real opinion. At the end of the day, it is often too expensive to pursue claims against individual consumers.

Anyway, cool project. Keep posting pictures of the progress.

 

[essenmeinstuff]

caution on this. The above statement is mostly correct in the EU. US law is much more strict. Even for personal use.

In the case of the EU, I would think the definition of personal use could be debated if such use included use by a professional racer. Consult an attorney for a real opinion. At the end of the day, it is often too expensive to pursue claims against individual consumers.

Anyway, cool project. Keep posting pictures of the progress.

Ah right.

http://www.iusmentis.com/patents/crashcourse/rights/

Didn't realize the US had tighter regulations regarding this!

 

[Wilhelm]

I designed a G-Boxx bike last year, I used a Horst link in the rear, but It doesn't need a tensioner. Then I heard that G-Boxx 3 was comming so I'm waiting until I know how it is...

Vrock, how did you solve the problem of chain grow without a tensioner?

 

[Vrock]

In my design the Horst Link was as close as possible to the wheel axle, and it was in Line with the Chainstays so the chain length didn't change much through the travel, it was only 0.01mm or something like that, It will affect chain tension a little but I was hoping that it didn't need a tensioner.

 

[Wilhelm]

I see, so it should behave at least in terms of chain grow more like a SplitPivot (chain grow along the axle path = 0 ) than a Horst link that is much more distant from the rear axle resp. lower than in your design.

What a pity that the release of the G-Boxx 3 will happen not already these days but next year or even later.

 

[TrueScotsman]

Just a quick update- I have been away working for a week and nothing much has happened to further progress on the bike other than;

I have spoken to the waterjetters who have to re-jet (?) the alu linkage plates as there was a file conversion error with the original ones.

Me and my Dad have been working on the rear split-pivot dropouts (no pics to show yet unfortunately :-( )

I have taken some of the alu to a forum member on Descent-World who offered to help out with milling it (may have pics for the weekend)

As for the time question; ETA is out the window! I had hoped initially (naiively!) that it may be finished by the final Scottish DH series race in a week and a bit's time, BUT there ain't no way that will happen! So, I've decided not to rush things and take my time and do things right! Especially as my right hand man (my Dad) is going on holiday for a week.

So this means that I have to get my cracked Morewood given a quick-fix weld (I know it won't be as strong!) in order to race down the infamous Ft. William WC track. Hmmmm!

So, until more interesteing news!- Over and Out.