New Design for a DH Race Frame

[jeremy_2640]

What improvements need to be made. Bull bar and roll cage please

1.5 Steer tube so 0 stack head set can be used to keep front end low.

Alls balls bearings standed. No cage just balls.

Greasable DU bushes.

I was wondering when you'd make some suggestions Calv, its a pretty safe bet that it will have a big bull bar and perhaps some orange lights all the way down the side haha ... whats the reasoning for DU bushes as opposed to ball bearings?

Also thanks for a well thought out post Ajay... There's still some of the forum heavy weights left to post their thoughts...come on guys....

 

[spinner]

I'd like to see all pivots go to greaseable bronze bushings over bearings.

Rotation isn't the main requirement , but load bearing is. What are we talking in rotation , 20 degrees .... 30 ? Bushings are easily replaced (as easy as bearings) and have a greater surface area. Seems logical. For mass production , I guess bearings are cheap and quick to fit.

 

[s_t_3_v_3]

What do you like about existing products (DH frames)?

They are good quality products that you can expect to trust. They are strong and hard wearing.

What do you dislike about existing products (DH frames)?

They can be heavy, bulky, and annoying. They are harder to manouver than lighter styles such as light freeride bikes etc. It would be cool if they were as manouverable as freeride and freestyle style bikes.

What are the most important issues you consider when purchasing a DH bike frame/bike (not considering componentry)?

The function and how it feels to ride. I would look for something thats gonna last a long time and not become obsolete in technology in the near future. A good quality build is important to make you feel safe as you ride it so you dont feel like its gonna break. it needs to run smoothly, especially with as little noise as possible (as it creates a mental image that your riding smoothly).

What improvements would you make to the products?

I dunno how you would do this but i find with current designs that the faster you go, the smoother it gets, so if you could somehow make the geometry so that the bike is smooth when going slowly, then as you speed up, the geometry changes to remain smooth similar to a current design. I dont know if you've seen the Millyards Downhill bike but maybe try looking at that to get some ideas.
The rear shock apparently auto-adjusts to the terrain to make the shock softer, harder, faster or slower depending on what your riding. Maybe if you could somehow incorporate this into the fram design rather than the shock so that the geometry changes to accomodate these terrrain changes, as the track become rougher, or smoother or whatever..

What specific features/atttributes and characterisitics do you desire in a DH race bike frame?

A rig that remains a constant feel on all terrain without change in efficincy of the bike. A low centre of gravity allowing you to dig into corners more. A good braking system such as that on the Kona DH range with the floating brake, preventing shock lockup.

good luck with your project.

 

[bjmtb]

What do you like about existing products (DH frames)?


There are many downhill bikes out there on the market, all catering for different fields. I am impressed with the level of options one has in purchasing a bike to suit their needs.


What do you dislike about existing products (DH frames)?


There is not enough good bikes out there with a high level of perfarmance for racing downhill. I think the main let down is funding.


What are the most important issues you consider when purchasing a DH bike frame/bike (not considering componentry)?


Weigh, Frame size, strenght of frame (these are three issues many would be looking at), however the most important issues are suspension set up (ie travel), pedal efficiency (majorly important), head tube angle, and bottom bracket height. In my opinion there is only a few bikes which can perform on such a high level on all of those needs. Foes bikes have it machined to perfection, I think the most important thing is research, taking the time to develope the original design.


What improvements would you make to the products?


That all depends on what bike you ride, take a Foes DHS 2:1 Mono for example (yes i have ridden one many times). there is next to nothing that would improve such a bike. really the only problem with any downhill bike is the points of movement (headtube, bottom bracket, pivots etc). there is a lot of wear and maintenance required to keep these moving parts in good condition. This also comes down to cost, ideally it would be benefitial to use titanium, howvere the cost is just too much. On another front, the asthetics of a bike are very important. Riders want their bike to be good on the eyes, not some bits of metal welded together that looks like a plucked chicken.



What specific features/attributes and characterisitics do you desire in a DH race bike frame?


Personally the key things are: The overall feel of a bike (you have to feel like you want to ride it, fast). suspension (a good shock makes all the difference), pedal efficiency is a must, the bottom bracket height for centre of gravity (turning), head tube angle, frame size, asthetics (a nice looking bike), well designed chain guide, overall handling and the strenght and stability of the frame.

 

[juzz]

I just say dump it and big rims.

 

[whitey89]

What do you like about existing products (DH frames)?
Streamline and simplicity

What do you dislike about existing products (DH frames)?
Bulky/ Chunky frames, heavyness, complicated pivots

What are the most important issues you consider when purchasing a DH bike frame/bike (not considering componentry)?
Weight, size, cost, maintainance issues, pedal efficiancy

What improvements would you make to the products?
Lighter, cheaper, simple swing arm/pivot design, easy access to shock, easy to clean, not too many bearing/stuff to go wrong!

What specific features/atttributes and characterisitics do you desire in a DH race bike frame?
Large travel (over 8" is ok), simple to maintain/clean, compatibilty with a range of components (ie dont make a frame that has for egxample an eye to eye length that only one brand puts out.)

Good luck with it, what course/ uni are you at?

 

[jeremy_2640]

What do you like about existing products (DH frames)?
Streamline and simplicity

What do you dislike about existing products (DH frames)?
Bulky/ Chunky frames, heavyness, complicated pivots

What are the most important issues you consider when purchasing a DH bike frame/bike (not considering componentry)?
Weight, size, cost, maintainance issues, pedal efficiancy

What improvements would you make to the products?
Lighter, cheaper, simple swing arm/pivot design, easy access to shock, easy to clean, not too many bearing/stuff to go wrong!

What specific features/atttributes and characterisitics do you desire in a DH race bike frame?
Large travel (over 8" is ok), simple to maintain/clean, compatibilty with a range of components (ie dont make a frame that has for egxample an eye to eye length that only one brand puts out.)

Good luck with it, what course/ uni are you at?

Thanks for your input mate, I'm studying Mechanical Engineering at Swinburne Uni. in Melbourne...

 

[cheggy]

What do you like about existing products (DH frames)?
Slacker head angle, around 65 degrees. Low bottom bracket, longer shock length, low stand over height, shiny colours are also a plus.

What do you dislike about existing products (DH frames)?
Heavy back ends, long head tubes are nasty too. Keep the stack height short and the front end nice and low.

What are the most important issues you consider when purchasing a DH bike frame/bike (not considering componentry)?
Weight, top tube length, chain stay length, pedal efficiency. A nice light rear end to flick the back out is good.

What improvements would you make to the products?
Maintenance free, bearings that don't come undone. Low to the ground.

What specific features/atttributes and characterisitics do you desire in a DH race bike frame?
Adjustable geometry is nice, like on many of the single pivots out there.

 

[Calvin M]

Sorry should of said shock DU bushes. They are always dry of grease when you pull them down.

If ball race bearings are being used they should be the type that are full of balls no spaces between balls (no cage). Much more suitable for high inpacks but not suitable for high rpm.

But as Tony said bushes are not used enought on bikes. I have greasable bushes in the bottom linkage of my ecd. As the needle roller bearings dont last at all and give the rear end a lot of flex.

 

[jeremy_2640]

Anyone else have an opinion...? Please let me know...

 

[eyes]

DH design

What do you like about existing products (DH frames)?

1. Frames are getting lighter - can build strong DH bike full build 17-18kgs
2. Movement towards VPP bikes with pedalling efficiency, ie Santa Cruz V10, Intense Socom, M3, M6 etc
3. 150mm/165mm rear axle width, wide BB housing 100mm, 1 1/8" 1.5" hybrid head tubes improving stiffness
4. Gear box drivetrain - ie. G boxx 1 and G boxx 2 like Nicolai TST Evo - keeping centroid of bike where it should be - right below the centoid of the person and as low to the ground as possible.
5. Gear box again - mechanical efficiency of normal drivetrain can go down to 80% in shit conditions - gear box maintains 96-98% at all times.
6. Suspension design incorporated with Stable Pedalling Valve (SPV) shocks.

What do you dislike about existing products (DH frames)?

1. Bikes sticking with boring old deraillier based drivetrain.
2. All the above options equal expensive (building up a TST Evo would cost AUD15,000.

What are the most important issues you consider when purchasing a DH bike frame/bike (not considering componentry)?

1. Geometry suited to normal riding locations/style
2. Weight Vs Strength
3. Is it just dinosaur technology with gussets and SPV.

What improvements would you make to the products?

See above comments

What specific features/attributes and characterisitics do you desire in a DH race bike frame?

1. See above comments on centroid, stiffness, geometry, strength, weight
2. Good cable routing - can they go internally to save them in the continuous crashes I have?
3. Will update again over weekend with more thoughts.

Eyes

 

[jeremy_2640]

Thanks for your comments eyes, I was wondering how long till someone would mention the G-boxx, it's definately an option at the moment - I've been thinking about it for quite a while now. I'll see how it goes in the concept selection....

 

[BUSHPIG]

What do you like about existing products (DH frames)?
Large tubing and semi-slack head angles
What do you dislike about existing products (DH frames)?
NOTHING
What are the most important issues you consider when purchasing a DH bike frame/bike (not considering componentry)?
strength through the whole frame, 8-9 inches of travel, 68 degree head angle.
What improvements would you make to the products?
more efficient peddling, bottom out restrictions (so you cant hit the tyre on your seat for those who like low seats).

 

[JSPhoto]

4. Gear box drivetrain - ie. G boxx 1 and G boxx 2 like Nicolai TST Evo - keeping centroid of bike where it should be - right below the centoid of the person and as low to the ground as possible.

I forgot about that! that commen can be added to my input, G-box would be a nice inclusion

What improvements would you make to the products?
more efficient peddling, bottom out restrictions (so you cant hit the tyre on your seat for those who like low seats).

Totally agree!! I'm so sick of hearing the dang seat rub on the tyre after a big drop or something similar.

 

[PSYCHO-T]

What do you like about existing products (DH frames)?
Strength, 7inches + travel, the smoothness of the ride

What do you dislike about existing products (DH frames)?
Weight, pedal bob, all the same designs, i'm wanting something new

What are the most important issues you consider when purchasing a DH bike frame/bike (not considering componentry)?
Weight, strength, options (ie; adjustable head tubes, shock options longer sorter,)

What improvements would you make to the products?
the stuff i just said, Light weight, all the good options. at a price thats ok

What specific features/atttributes and characterisitics do you desire in a DH race bike frame?
some thing thats is as nimble as a gazelle, yet feirce as a lion! without a large amount of movement under break preasur, can eat up rock gardens!

 

[eyes]

techy linkies

I'll see how it goes in the concept selection....

If you like G boxx check the 'Tech talk/Faq 06' link on the following website:

http://www.g-boxx.org/

You can obtain some CAD guides from here to work in with your design.

And check this sh*t out for some more inspiration:

http://www.pinkbike.com/news/allen-millyard-part-1-2008.html

Millyard is a genius with design - I think he is actually a rocket scientist.

Eyes

 

[jeremy_2640]

Cheers mate, I've got all the G-boxx files and have had a bit of a play with them, thanks for the pinkbike link haven't seen that yet...Absolutely love Millyards work...

 

[Lorday]

What do you like about existing products (DH frames)?
Durability and effectiveness

What do you dislike about existing products (DH frames)?
Curvy and over compicated designs, long swingarms (like KONAs)

What are the most important issues you consider when purchasing a DH bike frame/bike (not considering componentry)?
Price, and a good comprimise between weight and strength

What improvements would you make to the products?
Between super light yet super dtrong, when you crack that you'll be rolling in the $$$$$$$$$

What specific features/atttributes and characterisitics do you desire in a DH race bike frame?
Being light, strong yet not super expensive.
AND Good Geometry