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Thanks ben, looks like its custom or bust then. or 120 front axle.
Alex - I plan on making it not un-rideable in terms of handling and braking. If I can buy the tubes then beauty may come into it, may not though, some pretty shoddy looking 36"ers around.
Talk to Ted James (Ted James Designs) maybe, he has a workshop in Stroud and has made hub shells for his own projects from scratch.
I had a set of the Z1 Bombers with dual disk mounts. I bought them when I lived in Boulder, Colorado. Paid buttons for them too (in uk terms)
The Disk mounts IRC weren't standard size and I'd a helluva time getting an adapter to make Hope and then Shimano XT calipers fit. I never liked the feel of the forks either.
The kicker was when selling no one wanted them because of the double mount.
Edit: Again, my memory may be failing me, but I think Goldtech made a dual disk hub back in the day.
Why is one caliper mounted on the front of the fork?
won't the dish (or lack of)caused by two discs on a 100mm fork dropout, combined with the wheel size, make for a horrible and fairly weak wheel?
paul - because otherwise youd probably foul the spokes.
faustus - having spoken to my favourite wheel builder he said he has seen similar builds and they have been fine, see mountian unicyclists and the stuff they ride, with 14 gauge stainless spokes I should be fine. I am also thinking of running 120 up front.
Why is one caliper mounted on the front of the fork?
Because nobody makes mirror image calipers. Really, the front of the fork leg is usually a better place to put the caliper anyway.
My motorbike weighs 160kg, + 60kg of Northwind, and stops very nicely from warp speed with only one rotor. Admittedly, a rotor the size of a pizza, but still.
Considering the stupendous power of the best brakes these days it does seem like you're overcomplicating things but I do like a mad project.
"Just because" is a perfectly valid answer...
any updates maximus? : )
He's still doing a superman from the first time he pulled the brake lever 🙂
He's still [s]doing a superman[/s] trying to pull his head out of the brick wall from the first time he pulled the brake lever
😉
I remember when V brakes first came out. People would go on a test ride, and we had to warn them about the braking! Riders used to heaving on the anchors with cantis would grab the same handful of lever with a V and stop rather suddenly!
[i]Riders used to heaving on the anchors with cantis would grab the same handful of lever with a V and stop rather suddenly! [/i]
I had almost the reverse issue. Having ridden only disks for years I switched to a canti-braked cross bike. First time I braked on a wet, chalky downhill it took me 'til I was half way up the next hill to stop.
Same when I'd let my cousin try my mtb. He's French and grabbing a handful of 'back' brake to do a skid didn't quite have the effect he intended 🙂
Jamie - This is as far as I have gotten so far.
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Spacing between disc and spoke flanges has changed since I rendered the image. 110 OLD with 4 sizeable bearings, need to grind my own QR15 axle and also need to find somewhere for custom 14G spokes in the 370-380mm range else my flange diameters get huge.
Also depends entirely on the dual crown geometry (that I am yet to get hold of) and how much bodging would be required. Reasons for not using a double fixed hub are sealing issues but surly seem to do a double fixed 120 OLD with cartridge bearings so if this custom one doesnt work, those may be worth a shot, but the flanges are pretty tiny.
Mainly it depends on spoke lengths at the moment.
Full set up [url= http://www.ebay.co.uk/itm/Marzocchi-Bomber-Z1-with-CHE-Twin-disc-brake-set-and-wheels-Retro-/300954257550?pt=UK_sportsleisure_cycling_bikeparts_SR&hash=item461245888e&clk_rvr_id=601214920525 ]Ebay last year[/url]
There's more info on retrobike if you search
P20 - based on yours going for 300(!!!) it's unlikely to fit such big wheels in I don't think I'll be looking for those forks (although the hub looks good!) seems pretty rare as well, probably quicker to make my own.
thanks maximus.
love what a slow burner this is. and how totally overengineered it sounds, tho not in a position to pretend i can do the 'math'
doesn't sound like it'll break tho, or you'll have trouble stopping
what about the rest of the bike?
Jamie - The rest of the bike is on a back burner, I have a very good idea of what I am going to do for tube sets etc I just need to decide on rear axle spacing and head angle/mechanical trail to try and get it to handle like a 26" bike. My other project is coming first ([url= http://maxengineeringdesign.blogspot.co.uk/2014/02/the-homebrew-steel-29er.html ]shameless plug[/url]) as I would like a 29er before the 36.
I ask questions like this as I want to do a stupid amount of research to make sure I don't get further down the design stage for nothing.
But so far its looking like 110/120OLD front hub, Hope pro2 trials rear hub (or SS specific so 135OLD but may go to fatbike 190OLD), 100mm BB and a 31.6 post. Going to keep ATC as small as possible and it will of course have a 1.125" headset with a 44mm HT. I also want it to have 15mm axle up front and a 12mm axle out the back (if possible with the given hubs) with pinch bolts on each for extra security.
Decided against hydro brakes for the front at least as the piston movement in the lever is designed for one caliper, leaving me getting half the braking force at each caliper so not improving anything (apart from heat dissipation and resistance to the power mode of failure). The mechanical levers will be much easier to bodge either 2 lever bodies to one lever or incorporate a cheater system into the cable run to increase pull. Although I do still have concerns about the force still being halved or a huge amount of set up to get anything worth while.
As I said, its all in my mind atm and I have it down on paper in a few places but the 29er project is coming first in the funds department which is hindering the 36" project.
[i]the lever is designed for one caliper, leaving me getting half the braking force at each caliper[/i]
Hope V twin/TRP Parabox with both outputs sent to the front wheel?
You can get cable splitters for mechanical brakes - eg pull one lever which goes into the splitter and then pulls two cables for the calipers.
V-twin/parabox needs two cables going in so you could use a splitter as above but you're not really gaining anything other than having a semi-hydro setup.
This thread may be useful:
http://singletrackworld.com/forum/topic/bike-brakes-for-people-with-one-hand
this being the splitter EDIT - it's actually called a 'doubler'.
http://problemsolversbike.com/products/cable_doubler/
Clubber-very useful thread!
It seems no mater which system I use the force will be halved, just means heat build up is less likely to fail the pads, which is no bad thing. Maybe Ill use that mechanical puller and get on the squash balls for grip. It will be a lot simpler than either dual hydros or a semi hydro system.
need to find somewhere for custom 14G spokes in the 370-380mm range else my flange diameters get huge.
Well that's easy at least. Ben will remember my saga trying to source spoke blanks to make a double ended spoke - I eventually found a source at http://www.unicycle.uk.com/unicycle-parts/spokes.html - 371, 375 or 376 available, or they'll cut and thread custom length ones.
Well you're only providing X force at the lever so other than through leverage, you can't change that unless you have some sort of servo assist 🙂
But as we discussed a while back, I don't think it's really an issue - you're overengineering it IMO - a single, large brake would be fine.
aracer - I have looked at them and my calculated spoke lengths are ~378, I know you can get away with 1mm either side of that but am yet to speak to the person I would get to build the wheels if using longer nipples would be appropriate (I don't like to pester him with too many questions, I imagine I get annoying after any period of time). Those penny farthing spoke blanks are something I hadn't considered though, and in the correct gauge.
clubber - yeah, thinking about it properly (and not being a numpty) I don't need the same force in each caliper to equal a standard one, together they will equal a standard one, it's the equivalent rotor size I am after, dual 120's would give me the perfect rotor size but to make sure I don't gather too much heat in the pads and glaze them over or cause power absorption failure I have been advised for 160's.
Admittedly yes, dual discs are overkill, but it does cancel the reaction forces out and mean I don't need a custom rotor (which I am more worried about designing and making than a hub) or custom caliper mounts. All the safety critical bits are not my problem 🙂 .
Bit more info that may be helpful:
[url= http://www.retrobike.co.uk/forum/viewtopic.php?t=106317 ]Here[/url]
&
[url= http://www.retrobike.co.uk/forum/viewtopic.php?f=1&t=75618 ]21 pages on a similar project here[/url]
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thats from my post below.
I was going to link that photo when i saw it but i had issues with the hub.... i.e. missing spoke hole.
Doesn't help with the hub, but Magura do a setup with one lever to 2 calipers:
[url= http://pedicabshop.com/blog/perfect-twin-disc-brakes-big-magura-twin.html ]http://pedicabshop.com/blog/perfect-twin-disc-brakes-big-magura-twin.html[/url]
I had some reverse hubs on mavic 325 rims a while back that had mounts for 2 front discs. Lovely set of wheels that I only parted with due to the acquisition of a dh bike and needed a wider rear hub and part ex'd mine
http://m.pinkbike.com/photo/3457391/
[url= http://maxengineeringdesign.blogspot.co.uk/2014/04/a-36-wheels-are-dual-discs-necessary.html ]An update with graphs, drawing and picture[/url] on where I am at the moment. But making my bike frame jig had priority at the moment!
You're sure the Zee lever has twice the volume/pull as std levers?
AFAIK 4 pot calipers often use smaller pistons and hence the same lever.
Not sure at all, working off the assumption of larger piston area at the calipers so would be more suited to run two than the standard lever. Not an unfair assumption I dont think, hopes bores seem similar although that doesnt mean jack all about the piston area depending on the design as Ive never had one apart.
Ive got an adaptor for a non disc hub to convert it to a disc. Its made up of a flange that bolts the the hubs original flange with a 6 bolt disc part to bolt to. Ill try and dig it out and get a photo up.
kevs, something like this I assume, it could solve my 4 cross spoke length issues.
Very similar to that, was bought for a go kart project years ago and sat in the shed ever since.
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sorry about the crappy pics, but most amazingly was that fact i found it in the tip of a shed.
Why 4 cross?
I have to say I am not with you on your assumption. Any 4 pot calipers I've seen has way smaller pots. Do the Zee levers look any different to other shimano ones? You'd expect them to if you are correct...
[u]Cynic-al[/u]
The 4 cross is based mainly on trying to build a stiff a wheel as possible, penny farthing riders seem to use 4/5 cross most (although some use up to 7 cross) to build a strong wheel over that diameter. Seems the most sensible idea to me, more cross -> stronger wheel, especially if I am using the equivalent of a 360mm disc.
It is a pretty large assumption, I admit but its either that or my even crazier idea that I am trying to figure out of a positive pressure brake booster system, which will produce many OTB moments.
[u]Kevs[/u]
Looks pretty similar to the one I've seen as well. Have you ever had it fitted? How well does it/does it not clear the caliper??
never had it fitted as such im afraid, was used in such a way with sprockets instead of discs to have a certain gear without ground clearance issues. similar to the way guy martins speed bike had two bottom brackets.
how's about a bump for this thread maximus?
project still going?
My contribution although it's probably a year too late: if trying to use a double-fixed hub with screw-on discs, one of those threads will be the wrong way round and you'll completely rely on the lock ring to hold it on. Doesn't sound safe to me.
I do like the idea of bastardising two Deore hubs though. There can't be much torque going through the centre barrel so some epoxy & carbon matting would probably do the job nicely.
some epoxy & carbon matting would probably do the job nicely.
Now that sounds like job for me!
Jamie,
the project is still going, about to purchase spokes and rims after speaking with my wheel builder. When [url= http://www.broakland.com/dixie.html ]these guys[/url] get back to me then I will use their system on a ambrosia zenith double fixed track hub. My thinking being if its good enough for track riders to brake against a lock ring then it is good enough for me (probably fine), and I will use thread lock on both the adapter and the lock ring. As it is a track hub with cartridge bearings I will be making my own lockring/nylon washer to provide a hope style shield from mud to avoid having to strip it down after every ride. I am still waiting for broaklands to tell me if I should buy the phil wood/campy lockring of the ISO, seen as sheldon says that ISO is the campy standard and JIS is the shimano *confused*.
I have a hope pro 2 evo trials rear hub now ready to build up for the rear wheel and I have some 2010 boxxer crowns to make my forks with to avoid having to buy a crown race cutter, thankfully the hub fits in between the stanchions so it *should* be an easy fix. Weirdly I will also be making my own stem, two of them infact, to attach to the stanchions rather than the standard clamping point for bars (think the way clip on aero bars work).
I am going to use 3 (yes 3) BB7 road calipers as that is what I have lying around, I have the brake levers (some chepo tektro ones from on one) now and will use something similar to a jteck double pull adapter to pull both levers and equal amount, again this is something I will make.
The rest of the build is still going, currently trying to validate some of the FEA testing on a formula student car, once this has been done then I am confident that a bicycle will be validated as well given how simple it is in comparison. I have decided on using plain gauge T45 tubing as its cheaper and I will be using fat bike standards at the rear end (100mm BB and a 135mm rear hub offset by 15mm, think a surly pugsley) which means I can split the seat tube to make it look a bit like a fork and have some super slammed chainstays to make it not handle like a boat. Need to finish deciding on geometry (which I will be going over to mtbr for advice on, as they seem to know their stuff) then I will be able to buy tubes and get brazing!
Sorry for the essay but you did ask 😉
Oli - you are getting no where near this build!
edit: almost forgot! I am moving away from 4x and to 3x because I can only buy the length of spoke required for 3x, I am having to vary nipple size to build the wheel properly, which is fun.
Oli - you are getting no where near this build!
😥