[Closed] An out there bodge quesion

forks with disc mounts are pretty cheap and abundant now, even for road.

Links please, I've not found that many at reasonable prices.

This for a start: http://www.cyclesurgery.com/pws/UniqueProductKey.ice?ProductID=CKNS0001KK

I've already got a set of those 😎 they're not that light IIRC!

I guess your definition of cheap differs from mine!

Maybe 🙂 However, how much is it going to cost to bodge some - machining generally isn't that cheap then you need some epoxy and matting plus a fork in the first place.

Don't suppose you're selling the DC19?

I've already got a set of those they're not that light IIRC!

I guess your definition of cheap differs from mine!

No, but they are reasonably cheap (compared to a lightweight road fork), reasonably light (compared to the cheaper and functionaly similar 700c P2 - 650g compared to ~1000kg) and are well thought out in terms of the detailing (I've got two pairs and haven't found anything to beat them).

At the moment, to get anything better is truly moon-on-a-stick material (IMO).

Clubber - I still have the 700c P2's mentioned you can have for peanuts if you're after something like this.

No Clubber, not for sale.

650gm is not ringing a bell for me...point is I do have some forks and frames, am on a budget, and like projects like this. It's annoying that the DC19s have no rack mounts.

I also know how long it would take to knock up what I am asking for!

I also know how long it would take to knock up what I am asking for

Which is fine - the bit you don't know is how long they would take to fail as, per the other thread, you CBA to do the calcs (or let Toys do them!) 😉

They won't fail, the method of mounting them might, seems to me if you slap enough carbon on there in a well thought out way then you should be fine, certainly on the frame, which takes less forces from the caliper.

How are you going to define 'enough' without it weighing/costing tonnes? Without any form of calculation it's thumb-in-the-air and trial and error.... in fact, nevermind. You're heart is set on doing this so [i]bon chance[/i] and make sure the helmet-cam is recording!! 😉

I've seen a fork with rack mounts and a disc mount - Karbona is the brand. Can't find it easily but Performance Cycles used to sell them.

http://performancecycles.co.uk/

You'd need to call them though

bristolbiker - Member
How are you going to define 'enough' without it weighing/costing tonnes? Without any form of calculation it's thumb-in-the-air and trial and error.... in fact, nevermind. You're heart is set on doing this so bon chance and make sure the helmet-cam is recording!!

I've had mounts welded on to various frames and forks that have worked fine (and one that didn't). I don't think the frame builders spent too much time on CAD packages in the process. Sure there's an element of guess work.

I guess I'd rather be the guy that makes his own stuff and has fun experimenting, like I have done in the past, than be the web-drone saying "you can't do that".

Questions

Do you know what the magnitude of the forces is ( clue - shedloads)
Is the frame and forks designed to takes this loading?
Is the frame and fork strong enough to take the loading?
Do you you have a jig to ensure the mounts are placed with sufficient accuracy?
Do you know how to bond 2 dissimilar materials together with a third material?
Are you well insured?

I guess I'd rather be the guy that makes his own stuff and has fun experimenting, like I have done in the past, than be the web-drone saying "you can't do that".

I guess I'd rather be the guy that makes his own stuff and has fun experimenting, like I have done in the past, than be the web-drone saying "you can't do that".

I've had mounts [b]welded[/b] on to various frames

That is the point - welding is a world away from what you are proposing. My day job is strength and fatigue assessments for metal and composite structures, so look elsewhere to hang the web-drone tag thanks. I never said it couldn't be done.....

OK I'll play a little...really TJ, did you even read my post? Do try harder! 😀

Questions

Do you know what the magnitude of the forces is ( clue - shedloads)
Is the frame and forks designed to takes this loading?
Is the frame and fork strong enough to take the loading?
Do you you have a jig to ensure the mounts are placed with sufficient accuracy?
Do you know how to bond 2 dissimilar materials together with a third material?
Are you well insured?

Bristolbiker, if you've got expertese and have something helpful to give me then I would be glad to hear it rather than hear you take the **** from a position of expertese.

At what point did I take the ****? I simply said that if you weren't going to do calcs then trial-and-error and (probably) several versions is the only option open to you and wished you good luck. All the factors that you need to consider to get it work are WAYYYYY beyond a few words on an internet forum - to get it to work first time and sign it off as such would be a reasonably sized commercial project.

You make me laugh

Of course I read your post. Its clear you really haven't a clue. A quick back of a fag packet calc give around 500 kg as the max force thru the fork mount, less on the rear, the post mount is off centre on the fork so there will be a twisting / side load on that. The caliper mount is offset from the pads so another twisting force generated. These could add up to hundreds of kilos. Its really very highly stressed.

So a bit of CF wrap with some room temp curing epoxy is going to be strong enough to contain a off centre force of hundreds of kilos?

I know we all like a pie in the sky idea but this one is frankly ridiculous.
Teh caliper has very little tolerance for misalignment in some directions.

TJ you make me laugh too, with the mitigating factors you've clearly not identified.

BB my profuse apologies but I took your "bon chance" and helmet-cam comments as less than genuinely well-intentioned...are you up for helping a poor commercial lawyer with some left over screw-fix eposy and enough in his pay-pal to buy some ebay carbon out?

What mitigating factors? Nothing can reduce the magnitude of the forces involved nor willbe able to suddenly make the frame be able to resist force in the directions it was not designed for

you're wasting your time Teej and Bristolbiker and others. I already offered Al a free calc service to help him along and stop him from being "bullied" but he doesn't want it, this is essentially a troll and not a real request for help advice.

Digested thread:

Al "I don't really know anything about engineering but I fancy trying this"
Miserable nayasyers "never work yer a pillock"
Optimistic and knowledgeable helpers " yeah go on Al if you do x or Y it might help, let us use our expertise to see you through this fun little diversion"
Al "no thanks, despite knowing nothing about engineering I think I'll maintain my cool we b persona by making out I know better than you, and I'm loving the attention so I'll keep being obtuse until I fall of my poorly modded bike and hurt my little ego"

Al - I know it "can" be done (shhhhh - I had a hand in a prototype to test something for, er, somebody.... NDA's prevent further detail), but it was ugly as sin and even then had only sufficient strength for the intended bodged test before it fell off.

If I was going to do it again I would bring the full power of my commercial tools/software/instruments on it and do the science properly as, IMO, to let it loose in the real world on such a safety crital area was madness - and TBH, I don't have the time right now (and the time required would be obvious around the office).

Happy to offer hints and tips as you go along, but without doing to the n'th degree as above, you're man-in-a-shed approach is as good as it'll get with all the caveats that go along with it.

Erm OK look at frames and forks not designed for disc mounts beside those that are. Are the tubesets significantly bigger? Often not, so stiffness will be similar, and often there is no brace either.

The disc/wheel itself offers a stabilising effect resisting torsional forces.

I don't really see any issues in overcoming the below; you may not know but I've made & used various components for bikes previously.

Teh caliper has very little tolerance for misalignment in some directions.

toys19 you've missed the bit where I've said I'll take you up on your kind offer, perhaps you can retract your comments before a bullying complaint has to be made 😉

TJ - please check your units 🙂

BITD Hope's first mech disks were held on with a machined axle bit and a jubilee clip around the fork leg

[url= http://www.retrobike.net/forum/viewtopic.php?t=94741&postdays=0&postorder=asc&start=0&sid=766f53df81363ff66a432826337c5085 ]see here at retrobike...[/url]

Are the tubesets significantly bigger? Often not, so stiffness will be similar, and often there is no brace either.

But the carbon forks with tab fall into two camps a) the tab is metal and integral with the drop-out, this is then bonded to the carbon blade(Pace, Kinesis) or b) fully integrated carbon tabs into the carbon blades (Woodman et al, IIRC). There are reasons why bonded metal/carbon/metal isn't a good way to go, some are commercial, some are pure engineering/materials

kiss kiss I have missed it, oh well it was fun writing it and made me laugh!

edit - where exactly, I can't find any acceptance of my offer???

Knowing the force the caliper sees isn't going to help, because you don't know what force the 'bodge' can take. So as has been said before, make it as 'strong' as possible and see if it works.

The disc/wheel itself offers a stabilising effect resisting torsional forces.

Hahahahahahaha. 🙄

Its the interaction between the disc and the caliper that produces the torsional forces.

Teh same thing cannot mitigate it. A disc has almost no lateral stiffness - it just flexes. So as you put the brake on the caliper will be pulled both forward with a force of many thousands of newtons and into the centre of the bike with a force of mmany hundreds of newtons. hitting bumps will add a shock load to this as will teh initial application of the brake

you are also twisting the forks

toys see the other thread.

I will send you and BB hugs and daft questions by email if I may, at least you are not pissing in the wind and attacking me personally like so many others 🙄

There are those that do, and those who come up with a million reasons not to - which mainly boil down to "it may not work".

Cynic-al obviously has enough nous to realise it's a trial and error process and at his own risk. It has to be for anyone who does not have the full resources of a lab and engineering workshop.

If it wasn't for bodgers we wouldn't be riding bicycles.

TJ is right that there are some fairly heavy loads being applied, but there are plenty places on a bike where there are heavy loads and we use carbon and epoxy.

If I was doing what cynic-al was proposing, I'd build a test piece first and bolt a long lever on it to see what would make it fail, but I see nothing wrong with trying the idea. As he says, throw enough carbon and epoxy at it and it should work (and still not be particularly heavy).

Anyone thinking of doing the same could read up on the W.E.S.T. system for some useful guidance (wooden boat oriented, but I have found it useful in the past).

So TJ if you hold a wheel rigidly and apply a twising force to the disc where the caliper grips it, there is no resistance to that force?

Please now leave this thread alone. I will not engage with you further.

This twisting force is around the fork leg - on the disc it is towards the centre line - and the resistance will be minimal as the disc flexes easily

The disc does not have anything like enough stiffness to resist a force of hundreds of newtons in to the centre line of the bike ( parallel to the wheel spindle of the bike

This force is produced buy the fact that the caliper mounts are offset towards the outside of the caliper not oin its centre line

Its o funny that you don't want to listing to anuyone who disagrees with you

So - material science. Do you know what material the frame and fork is made of? Do you know if the resin t#you intend to use is compatable?

Al - yes, by all means wibble away on email as and when you make a start....

I have just been looking at the retro-bike site at the early Hope callipers.

Looks like an obvious solution to the problem - use a disk brake adapter like those available for back brakes. Did anyone make one for the front?

Winstanleys are selling the A2Z Universal Disc Mount Adapter:
[img] [/img]

yes Al I am looking forward to helping in any way I can, I think a few fag packet sketches such that I or BB could make a calc or two would help..