Diy Bike ...ideas, Suggestions, Improvements

[Alex Dark]

Interested to see how this pans out

If I have any thoughts once your designs are uploaded Ill let you know

Ideal thanks man, feedback is what i'm looking for

have the magura mounts underneath the seatstays so it's got a clean profile to the frame

I've got an even better idea than that

Yes, come on Alex, I have been waiting patiently to see how this is getting on for long enough now.

Pictures please.

They will be up shortly...having some problems getting the seatstays to surve properly in solidworks at the moment

That will affect the operation of the brake though, same as reverse 4 bolt mounts on forks. In theory it should increase the hold backwards (on the edge of blocks) as the pads will be pulled backwards through the frame, as a result bite will be reduced.

I dont know if its been tried before though.

Yep, considered the above as well...so ive come up with a new solution

[psycholist]

There's one more fundamental very good reason for putting the magura mounts on the top of the seatstays - given very short seat tubes are the standard, there's no space to mount the brakes between the seat and chainstays with standard bolts anyway, especially if you factor in trying to get tools to it... Customising the frame with proprietary clamps for the brake pistons would be interesting but a serious design headache.

Based on some of the clearance issues between Maguras and cranks thanks to small frames, wide rims and very thick CNC brake pads, using one of the longer DH BB setups could guarantee clearance between the Magura pistons and every crank on the market regardless of how far out the Maguras are. There are a few DH specific 83mm shell BB's around and thanks to Hollowtech II, you can pick whatever BB width you like provided you can get a BB axle machined to suit. You may need a wider rear hub to maintain the chain line, but building the frame to sit the hub off centre so you can build a dishless rear wheel into a 6 speed freehub would be very cool indeed - definitely need to get some CAD modelling together before you build something like that to check for chain/tyre interference...

[Alex Dark]

There's one more fundamental very good reason for putting the magura mounts on the top of the seatstays - given very short seat tubes are the standard, there's no space to mount the brakes between the seat and chainstays with standard bolts anyway, especially if you factor in trying to get tools to it... Customising the frame with proprietary clamps for the brake pistons would be interesting but a serious design headache.

Based on some of the clearance issues between Maguras and cranks thanks to small frames, wide rims and very thick CNC brake pads, using one of the longer DH BB setups could guarantee clearance between the Magura pistons and every crank on the market regardless of how far out the Maguras are. There are a few DH specific 83mm shell BB's around and thanks to Hollowtech II, you can pick whatever BB width you like provided you can get a BB axle machined to suit. You may need a wider rear hub to maintain the chain line, but building the frame to sit the hub off centre so you can build a dishless rear wheel into a 6 speed freehub would be very cool indeed - definitely need to get some CAD modelling together before you build something like that to check for chain/tyre interference...

oh yes..im having lots of those. Hoping my idea will be revolutionary, my tutor seems to think that the frame will be pretty clever when it's finished.

Im just going to use a 128, 68mm bb shell...although it will be fully cad modelled to check just in case

[Alex Dark]

Right...so here we are after a massive bump.

Projects stands thus;

* Bottom bracket, Magura mount and all tubes barring seat tube fully cad modelled

* Pages and pages done on aluminium research with the conclusion that the 6000 ( 6061 ) aluminium will have to undergo 2 heat treatment stages to regain it's t6 temper.

* Magura mount has been fully designed, and tested on CAD

Attached are pictures of the BB yolk, Magura mount system, Frame assembly ( very rough ), dropouts and headtube. Tomorrow I'll have the first proper part assembly renderings finished.

All comments welcome, especially possible improvements.

[trialsmax04]

Alex i cant wait to see this finished. But i would seriously keep try and get some copyright on it as its starting to take shape. some of the ideas especially the magura mount very special indeed.

Having not read the whole thread, whats the geo going to be like?

max

Edit: Bit confused about the magura mounts. Will the cross over run through the frame? And how can you do up the clamps? Surely drilling holes for an alenkey/ bolt would weaken the thin top piece too much?

Will it be stiff enough without a seat tube?

Anyway looks really good.

max

Edited December 15, 2009 by trialsmax04

[Dr.scratchensniff]

I would seriously question the strength of this. You're going to be Putting a lot of force through the welds. Unless you weigh less than a 10 year old, it just won't hold.

Then again, considering the current weight of 10 year olds, even they might not be light enough...

[Alex Dark]

I would seriously question the strength of this. You're going to be Putting a lot of force through the welds. Unless you weigh less than a 10 year old, it just won't hold.

Then again, considering the current weight of 10 year olds, even they might not be light enough...

Dude, come on....there's a picture just below it with a toptube

I'm putting in a seat-tube as well...just not so sure how i want it to go. Maybe coustellier style, or possibly a la rockman slate.

Geo is 1085, +35, 380, 71.5 ....so far anyway

Ill bang up a picture of the magura mount with the slave in if i have time today Max

[trialsmax04]

I would seriously question the strength of this. You're going to be Putting a lot of force through the welds. Unless you weigh less than a 10 year old, it just won't hold.

Then again, considering the current weight of 10 year olds, even they might not be light enough...

I think this picture is to show just the down tube, chainstays, bb yolk and head tube together. I presume the finished frame would be the one above this picture including the top tube and seat stays.

edit: beaten to it!

Yea that would be cool alex, seams like its coming allong rather quickly now.

Edited December 15, 2009 by trialsmax04

[Revolver]

Yoke!

[monkeyseemonkeydo]

With regards the BB yoke: SHARP EDGES!! Get that shizzle smoothed out or you'll just end up with stress raisers and headaches. Also I hope you have access to a 5 axis CNC machine?! Other question is also with the brake mount. Are the threaded holes through or blind? If they're blind I can see you having trouble tapping them through the allen key access hole in the top. You've probably considered that but just in case . Overall looks good though!

Edit: The 'SHARP EDGES' also stands for the dropouts and possibly the seatstay section too. Just whack some rads on there and you'll be laughing.

Edit 2: There's a lot going on in there. Lots of corners and edges that just end abruptly at the lightening holes. If possible I'd try and smooth things off and make it 'flow' better in the design sense...

[Dr.scratchensniff]

Dude, come on....there's a picture just below it with a toptube

I'm putting in a seat-tube as well...just not so sure how i want it to go. Maybe coustellier style, or possibly a la rockman slate.

Geo is 1085, +35, 380, 71.5 ....so far anyway

Ill bang up a picture of the magura mount with the slave in if i have time today Max

As long as there's a seat tube going in too it should be mint.

I'd also agree with monkeyseemonkeydo. Sharp edges are your enemy.

However, it should be a beautiful bike.

[Alex Dark]

I think this picture is to show just the down tube, chainstays, bb yolk and head tube together. I presume the finished frame would be the one above this picture including the top tube and seat stays.

edit: beaten to it!

Yea that would be cool alex, seams like its coming allong rather quickly now.

Sure would, toying with a few ideas at the moment

Yoke!

Touche, Just googled it and you;re right

With regards the BB yoke: SHARP EDGES!! Get that shizzle smoothed out or you'll just end up with stress raisers and headaches. Also I hope you have access to a 5 axis CNC machine?! Other question is also with the brake mount. Are the threaded holes through or blind? If they're blind I can see you having trouble tapping them through the allen key access hole in the top. You've probably considered that but just in case . Overall looks good though!

Edit: The 'SHARP EDGES' also stands for the dropouts and possibly the seatstay section too. Just whack some rads on there and you'll be laughing.

Edit 2: There's a lot going on in there. Lots of corners and edges that just end abruptly at the lightening holes. If possible I'd try and smooth things off and make it 'flow' better in the design sense...

IMG

Ah, I hadnt actually noticed how sharp it was I'll get right on that cpt.

As long as there's a seat tube going in too it should be mint.

I'd also agree with monkeyseemonkeydo. Sharp edges are your enemy.

However, it should be a beautiful bike.

Thanks very much dude...

Here's the new BB yolk.

Pictures of forks will be up shortly.

Edited December 15, 2009 by Alex Dark

[Matt Vandart]

Dude where the yoke bit meets the bb shell on the LHS there (and obv the right) it will be impossible to machine this like that in one piece need radius there too.

Edited December 15, 2009 by Matt Vandart

[psycholist]

It's coming together very nicely. The brake mounts look very weak though. I reckon unless there's a lot more reinforcement that's not obvious in place when the brake clamps are fitted, the mounts will probably buckle on heavy landings. Putting the brake pistons through the tube is a nice design detail, but it adds a lot of stress risers to the frame. The seatstays will stay mostly in compression, so they're less prone to fatigue than chainstays (Fatigue needs a tensile stress), but with all the cross section changes there will be local tensile stress all over the place now.

Definitely smooth out all the corners too - the edge where the BB shell and the chainstays join definitely needs a big fillet. Internal corners will be a lot harder to smooth after manufacture, so they're the priority, external corners can be dealt with by manually rounding the edges afterwards if there are manufacturing issues that make putting them in initially difficult.

[Alex Dark]

New screenshot of magura mount with clamps.

Dude where the yoke bit meets the bb shell on the LHS there (and obv the right) it will be impossible to machine this like that in one piece need radius there too.

Yeee, i was planning on welding the two together, lathing the bb shell in one go, milling the slots then later milling the yoke separately.

It's coming together very nicely. The brake mounts look very weak though. I reckon unless there's a lot more reinforcement that's not obvious in place when the brake clamps are fitted, the mounts will probably buckle on heavy landings. Putting the brake pistons through the tube is a nice design detail, but it adds a lot of stress risers to the frame. The seatstays will stay mostly in compression, so they're less prone to fatigue than chainstays (Fatigue needs a tensile stress), but with all the cross section changes there will be local tensile stress all over the place now.

Definitely smooth out all the corners too - the edge where the BB shell and the chainstays join definitely needs a big fillet. Internal corners will be a lot harder to smooth after manufacture, so they're the priority, external corners can be dealt with by manually rounding the edges afterwards if there are manufacturing issues that make putting them in initially difficult.

Well, the idea is to have seat stays that directly reinforce the magura mounting area. Ill bang up some more cad pictures in a moment to illustrate

Righto I'll re-do that now

Thanks for the feedback Guys.

EDIT: I reckon the gap between the plates that the magura clamps fit into could be decreased? hmmm...any ideas folks?

Edited December 15, 2009 by Alex Dark

[Alex Dark]

New filleted BB yoke

EDIT: Rainbird grammar check

Edited December 15, 2009 by Alex Dark

[Matt Vandart]

why dont you machine the mounts out of billet and have the clamps contained within. rather than that terribly flexy looking set up?

Edit:sorry missed the bit about making them thickerer.

New filleted BB yolk

Is that 2 piece welded?

Thinking about it again, seeing as the seat stays are mainly under compression why don't you just make them clamp the clamps if you get me.

A cut out in the machined bit allowing the clamps to move longitudinally with a very small clearance and then the bolts just go through that bit and thread in the other dise, rather than the spacers and crap mess around.

Edited December 15, 2009 by Matt Vandart

[Luke Rainbird]

Looks like you really took on board the "yoke" comments

[psycholist]

You'll need lots more fillet at the sides where the chainstays curve inwards towards the BB shell and at the bottom of the BB shell. Cracks will grow very quickly off those areas as their high tensile stress and already quite acute angles.

The brake mounts really don't look very strong at all. Fitting and adjusting the brakes to them will be a real pain since there's no way to loosen the brake mounts off properly without straining the frame. The V shaped slots in the chainstays look like a significant fatigue cracking risk too. If you're to get away with a setup like this try using C-Section bars for the top and bottom of the brake mounts to increase their bending stiffness so the chance of buckling or bending from braking force is reduced and use a rounded or flat cut on the seatstay where the brake mounts are fitted rather than the V cut.

[Alex Dark]

You'll need lots more fillet at the sides where the chainstays curve inwards towards the BB shell and at the bottom of the BB shell. Cracks will grow very quickly off those areas as their high tensile stress and already quite acute angles.

The brake mounts really don't look very strong at all. Fitting and adjusting the brakes to them will be a real pain since there's no way to loosen the brake mounts off properly without straining the frame. The V shaped slots in the chainstays look like a significant fatigue cracking risk too. If you're to get away with a setup like this try using C-Section bars for the top and bottom of the brake mounts to increase their bending stiffness so the chance of buckling or bending from braking force is reduced and use a rounded or flat cut on the seatstay where the brake mounts are fitted rather than the V cut.

As in on the chainstays themselves? or the bb shell?

Point taken....

Where are the V shaped slots ?

We talking U profile here?

[monkeyseemonkeydo]

Where are the V shaped slots ?

V shaped cuts:

The comments relate to the area where, in the BB yoke, the BB shell joins what is the yoke for the chainstays. If it were one piece it would be impossible to machine due to the acute internal angle and even if it were welded (if that were possible) it would still be an area of very high stress and likely spot for crack initiation.

[forteh]

I would be inclined to put a couple of spines/plates on the outsides of the flat section of the upper maggie mount (the booster could be extended on the lower to do the same job) to resist buckling; you could also extend them further up the chainstays to increase stiffness and allow more weld area.

Something like my bad photoshop

Edited December 15, 2009 by forteh

[trialsmax04]

Alex i have an idea for the brake mounts. Forget the idea of thin seat stays. Instead produce the stays like a normal frame, but machene the bottom part of the brake mount into the top of the stay. That way when the top part of the mount is bolted in, it will be an integral part of the frame. However to do this you need to have a weighty solid seat stay. Of which ihave no solution

anyway, i doubt it would work, just throwing up ideas.

[Alex Dark]

V shaped cuts:

The comments relate to the area where, in the BB yoke, the BB shell joins what is the yoke for the chainstays. If it were one piece it would be impossible to machine due to the acute internal angle and even if it were welded (if that were possible) it would still be an area of very high stress and likely spot for crack initiation.

Ah, I see what you mean. Those two pieces of plate will be welded together before being welded into the frame.

surely it would be able to be welded? hmm..ill check

Thanks

[Revolver]

That looks like a massive weak point