Bump!
Homemade Split Pivot Gearbox DH Bike
- Thread starter TrueScotsman
- Start date
Hey Ian, how are you doing with your frame? Have you already welded it? Keep up 
any news at all? I would hate for this thread to be made with all those teasing pics and then not find out how it finishes 
Cool.
First, big question:
How much suspension kinematics, stress and vehicle dynamics analysis have you done to your design? Please answer as detailed as possible
Second question:
What aluminum are you using? In case of the tubes, what profile are you using (ID and OD dimensions)
Third question:
Are you a ME?
Fourth question:
Is it a personal project, or a school project?
Cheers
First, big question:
How much suspension kinematics, stress and vehicle dynamics analysis have you done to your design? Please answer as detailed as possible
Second question:
What aluminum are you using? In case of the tubes, what profile are you using (ID and OD dimensions)
Third question:
Are you a ME?
Fourth question:
Is it a personal project, or a school project?
Cheers
First of all- sorry for the lack of updates- I been mega busy at work and have not had time to spend on the g-boxx bike.
BUT, because of Christmas Holidays I now have some time. So the build is back on! Woohoo!
To answer some questions;
First question-All suspension kinematics is self-taught (I highly recommend Tony Foale's "Motorcycle Handling and Chassis Design"). This bike is experimental- putting some of this theory to the test. All the designs were done on AutoCad (2d) and I haven't done any FEA, stress analysis, etc.-If in doubt I have oversized stuff (this bike won't break any lightweight records!)
Second question- The aluminium is 7005- from fairing.com. The Downtube, Seat Tube and Top Tube are round section (various diameters) and the Seatstay is 25x19 rectangular section. The Chainstay is tapered and is to be made from two bent channel sections welded to form a tube. Tubing thicknesses varies depending on the section-all are at least 2mm thick! (PM me if you need specifics)
Third question- No, I am not a Mechanical Engineer. I am an Architect by training but now run the family sales business. I have always had a design/engineering interest though (no doubt helped by my Dad's engineering background).
Forth question-Yup, this is a personal project- just for $hi+s and giggles!
Hopefully more info/pictures to come in the following days
BUT, because of Christmas Holidays I now have some time. So the build is back on! Woohoo!
To answer some questions;
First question-All suspension kinematics is self-taught (I highly recommend Tony Foale's "Motorcycle Handling and Chassis Design"). This bike is experimental- putting some of this theory to the test. All the designs were done on AutoCad (2d) and I haven't done any FEA, stress analysis, etc.-If in doubt I have oversized stuff (this bike won't break any lightweight records!)
Second question- The aluminium is 7005- from fairing.com. The Downtube, Seat Tube and Top Tube are round section (various diameters) and the Seatstay is 25x19 rectangular section. The Chainstay is tapered and is to be made from two bent channel sections welded to form a tube. Tubing thicknesses varies depending on the section-all are at least 2mm thick! (PM me if you need specifics)
Third question- No, I am not a Mechanical Engineer. I am an Architect by training but now run the family sales business. I have always had a design/engineering interest though (no doubt helped by my Dad's engineering background).
Forth question-Yup, this is a personal project- just for $hi+s and giggles!
Hopefully more info/pictures to come in the following days
this!Hopefully more info/pictures to come in the following days
Did you do kinematic/dynamic calculations by hand or did you use a software? Did you calculate the pedalling efficiency in certain gears, anti squat, brake squat, pedal feedback etc or did you just placed pivots in locations similar to Split pivot bikes?First of all- sorry for the lack of updates- I been mega busy at work and have not had time to spend on the g-boxx bike.
BUT, because of Christmas Holidays I now have some time. So the build is back on! Woohoo!
To answer some questions;
First question-All suspension kinematics is self-taught (I highly recommend Tony Foale's "Motorcycle Handling and Chassis Design"). This bike is experimental- putting some of this theory to the test. All the designs were done on AutoCad (2d) and I haven't done any FEA, stress analysis, etc.-If in doubt I have oversized stuff (this bike won't break any lightweight records!)
Second question- The aluminium is 7005- from fairing.com. The Downtube, Seat Tube and Top Tube are round section (various diameters) and the Seatstay is 25x19 rectangular section. The Chainstay is tapered and is to be made from two bent channel sections welded to form a tube. Tubing thicknesses varies depending on the section-all are at least 2mm thick! (PM me if you need specifics)
Third question- No, I am not a Mechanical Engineer. I am an Architect by training but now run the family sales business. I have always had a design/engineering interest though (no doubt helped by my Dad's engineering background).
Forth question-Yup, this is a personal project- just for $hi+s and giggles!
Hopefully more info/pictures to come in the following days
7005 Al is rare.. any reason you went for it instead of 6061 or the superior 7075?
Thanks for the responses, and very good luck with your project. Remember to do everything slow and perfect
You can weld it. 7075 = not.
weldability & 7000 series
Sorry I meant 7020.
why cant you weld 7075?
You get a lot of cracking in the weld.
can it just not be done at all?
I did most of my working out graphically on AutoCad- things such as shock leverage ratios, anti-squat percentages, etc. Anti-squat is simplified by using a gearbox as there are not multiple gear ratios/chain force angle.
As for Brake Squat/Anti-Rise since it is a split pivot I have the option of having the brake caliper attached to either the chainstay OR the seatstay to give different squat responses- neat, huh!
I will try both out and race with whatever I prefer.Pictures soon, I promise!
Is there even an issue if it is identical to a DW design. I always thought that a Patent protected the patent owner from having other people SELL their stuff? If you are making something for your own personal use I dont think that there is a darn thing anyone can do about it.
Just curious...
Oops.. read that link. I stand corrected.
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he said he spoke to DW and said if he doesnt sell it, then there wont be a problem
posted below that question
http://www.ridemonkey.com/forums/showpost.php?p=3507996&postcount=10
i was wondering about that too, where did you get the billet from?
OK- some pics!
First of the pics are the parts required for the LH split pivot- the chainstay dropout, the seatstay dropout, pivot spigot, axle and brake adaptor (as mentioned earlier). As the dropouts are quite wide I am using a 150mm x12mm Rockshox Maxle even though the rear hub is only 135mm wide. This gives me more room for the dropouts and bearing,etc. Anyway, here's the pic of the parts;
And a pic of the parts assembled (minus the axle locknut);
Right, gotta go now. Will post more pics tomorrow.
First of the pics are the parts required for the LH split pivot- the chainstay dropout, the seatstay dropout, pivot spigot, axle and brake adaptor (as mentioned earlier). As the dropouts are quite wide I am using a 150mm x12mm Rockshox Maxle even though the rear hub is only 135mm wide. This gives me more room for the dropouts and bearing,etc. Anyway, here's the pic of the parts;
And a pic of the parts assembled (minus the axle locknut);
Right, gotta go now. Will post more pics tomorrow.
That wasnt' my question... my question was in regards to the legality of it, which was answered in another post. i always thought that you could make anything you wanted for yourself.. just not to sell.
Some more pics;
This time of the shock linkage. The main shape was already waterjet cut out but it needed turned down to an acceptable thickness.
The parts;
The complete assembly (pre welding);
It's maybe still a bit thick- I may have to mill it down further.
This time of the shock linkage. The main shape was already waterjet cut out but it needed turned down to an acceptable thickness.
The parts;
The complete assembly (pre welding);
It's maybe still a bit thick- I may have to mill it down further.
These are great pictures Ian ! Let me ask you, what smallest radius was you waterjet able to work with? (How) Are you going to make radius on outer edges of you rocker-arm? How thick is the retaining wall of bearing housing (I mean the one with smaller diameter on the inner side of part)?
Let me ask you, what smallest radius was you waterjet able to work with? (How) Are you going to make radius on outer edges of you rocker-arm? How thick is the retaining wall of bearing housing (I mean the one with smaller diameter on the inner side of part)?
Just a wee update;
I've been concentrating recently on getting the g-boxx swingarm mounts done. The basic waterjetted shape needed milled down and then the bearing face needed turned. So here's some pics of the non-driveside mount (the driveside mount is also done but is far too TOP SECRET to show at the moment!!! ) Enjoy;
I've been concentrating recently on getting the g-boxx swingarm mounts done. The basic waterjetted shape needed milled down and then the bearing face needed turned. So here's some pics of the non-driveside mount (the driveside mount is also done but is far too TOP SECRET to show at the moment!!!
) Enjoy;
awesome this is one of the coolest things ever
I want to see this bike made so bad! keep up the good work!
moar!!!!!
Do you not have any CNC access?
Curious as to why you bother with the waterjet.
Gawd, doesn't everybody have there own CNC by now
Curious as to why you bother with the waterjet.
Gawd, doesn't everybody have there own CNC by now
great work dude.
Do you not have any CNC access?
Curious as to why you bother with the waterjet.
Gawd, doesn't everybody have their own CNC by now
I would have been stupid enough in my teenage years to try and make something like that with a drill, grinder, file and a hacksaw... CNC changes everything!
Hmmm, In hindsight I would get future projects CNC'd as it is taking so long to do by hand.Do you not have any CNC access?
Curious as to why you bother with the waterjet.
Gawd, doesn't everybody have there own CNC by now
What can I say- You use the tools at your disposal!
Cheers for the replies/encouragement!
Nice pictures. Ian, what are the 'precision' qualities of waterjet you used? What smallest diameter it was able to cut? How are you going to do all chamfering on edges?
Hi fluider, sorry i did't reply to you earlier post.
As for waterjet- smallest diameter I think is about 3mm- the jet is only about 1mm but I may be wrong(?) It is only precise to around 0.1mm but it is good at removing large areas of alu and doing 2d curves.
As for chamfering the curved parts - I am not planning on chamfering them (though maybe it will be a little ankle unfriendly!) unless anyone can recommend a good technique?
I only have a manual milling machine and a lathe.
This should suffice.
Favourite tool in my collection. So pro for chamfering steerer tubes.
This should suffice.
Carbide chamfer router bit in a Rotozip and a steady hand?
or a router bit with a bearing.. and also a steady hand
Looking good, can't wait to see more 