[Closed] Dual disc hub - anything like this around?

I am having issues finding a hub that has two for the front wheel

No shit!

No one's ever made them commercially (tho I remember a prototype in the 90s, before even standards were settled)

There was a guy in Cheltenham making them back at the turn of the century, can't remember his name

This isn't it but.. http://www.bikerumor.com/2011/09/24/gatorbrake-eight-piston-hydraulic-disc-brakes-with-carbon-fiber-rotors/

Id get busy with a hacksaw, some carbon fibre & resin and a pair of deore front hubs 🙂

what stoner said. Somethign with a 20mm axle and the disk half of two hubs.

If you cut them askew or machine castellations into them then the two halves will resist twisting a a bit too.

Mountain Cycles San Andreas bike with big old triple clamp forks had a dual front disc option IIRC
Hannabrink (sp?) fork maybe?

Id get busy with a hacksaw, a spoon, some carbon fibre & resin and a pair of deore front hubs

FTFY

Or, a Cully's DH Beast set up;
[img] [/img]

[img] [/img]

Yeah, someone in the 90s did them - was it middleburn?

Your fixed hub idea is probably the closest to being practical.

Though unlikely as I suspect it will be, it could be worth a word with Hope - they manufacture in house and setting up the CAD for this wouldn't be a big job (assuming that they have some CNC set aside for test pieces rather than all being tied up for production) and they might be willing to help on a project of interest (particularly if it was academic in some way).

So out of interest, why the need for double disk?

I've seen that on a really horrible looking cheapy bike (think it was £60 for the whole bike). Not sure if you want to go down that route though!

CA - I see it has been done, hence the interest

Stoner - Not a bad idea actually.. I like it.

Clubber - I doubt hope would be up for it but once I've done some cad there cant be any harm in asking I suppose. The project will involve a pair of 36" wheels each weighing in at around 5kg each, I would quite like to stop at some point so dual 180's on the front (with bb7's) and a 180 on the rear (4pot zee) should give me ample stopping power, someone has done custom dual disc with 210 rotors either side and nearly snapped their stem by grabbing too much brake so 180 would be ample.

One the hub is sorted, will you have to mount the none-driveside calliper on the front of the fork, as per the Cotic Roadrat?

non-drive side will be a standard IS mount, driveside will be as per roadrat fork (to even out the braking forces through the axle)

Found these:

[img] [/img]

[url. http://www.bikerumor.com/2011/09/24/gatorbrake-eight-piston-hydraulic-disc-brakes-with-carbon-fiber-rotors/
'Gatorbrake'[/url]

Do you *really* need double disc for that? People manage ok on 160s with 26" so assuming that the nominal wheel size is approximately right, 36/26 x 160mm = 220mm. You can certainly get 220mm discs.

The 5lb wheels aren't much of an issue really given that's a small weight compared to most riders and the bigger wheels obviously turn slower than smaller ones.

EDIT - just noticed it's 5kg - I'm still not convinced you really need double discs or at least not considering the associated hassle.

clubber - based on what ive read its either double disc, 4 pot w/ 210 rotor or 2 pot with custom rotor and mount. Considering the tyres weight 1.6kg, the rims weight 1.1kg and thats the rotating mass, its a lot to try to stop with one rotor, I would definately risk overheating riding downhill, even rotor warping at that kind of temp.

What clubber said - wheel weight is irrelevant here, the rest is simple maths, unless something such as awesomeness requires more power than usual.

Level double fixed hub is a possible.
You'd need custom rotors to match the cog fixing pattern though.

http://www.levelcomponents.com/tech.html

BETD might be able to do a custom hub?

I don't agree. How much do you weigh? Very heavy riders cope with reasonable sized discs unless they're riding the Alps (and brake dragging 🙂 ) and the wheel weight isn't that big an issue - as I said, it's rotating weight but it will rotate slower to the same degree as the size increase.

Anyone know the weight of a set of DH wheels and tyres?

hmm, i'm liking the sound of this proj!
can we get a sort of blog on the build, pics etc as you go along?
: )

But the wheel weight will matter, especially that far from the hub, I could get the same force at the tyre with a 220 rotor but that wouldn't slow me down as quickly because my wheels and bike (~20kg estimate) are that much heavier, at the same speed as a 26" I would have more energy to get rid of so I would brake significantly slower for the same tyre force. Even though it will have a lower rotating speed if its a pig to get up to speed it will be a pig to slow.

I weight 85kg on a good day.

TL - Ill give them a look, might be worth it, if not Ill just have to make my own.

edit:

Jamie - absolutely, but this will take actual designing and not geometry robbing like my current 29er project.

Just FYI, rotating mass effectively doubles the weight from a linear momentum point of view (assuming the mass is all at right at the outside of the tyre, of course in reality, it's less as the rim, etc are a bit closer in).

So, your 10kg 36" wheels compared to say 4kg 26" wheels are only making 12kg difference as far as the discs are concerned (for heat management purposes, the larger rotor will account for the leverage difference) - that's a bit under 2 stone. That really isn't critical. Or at least, not to the point of needing dual discs.

All IMO, of course.

but that would be front and rear, so I would have a stone extra to stop and slow (I think your forgetting how awesome it would look as well 😀 ), but based on the trouble it looks like I am going to have to go with a large rotor and some massive 4 pot calipers.

two 36" wheels = 10kg, right? so that's effectively 20kg linear mass
two 26" wheels = 4kg = 8kg linear mass

so total differnce for the bike is 12kg = 2 stone.

You're saying that a rider changing weight by 2 stone would require dual/different rotors. I'm saying that you might choose to do so but it is far from necessary, particularly given the hassle required. In fact my weight has varied by more than 2 stone over the years but my rotors remain the same size and I haven't died/turned my rotors molten yet.

It would look cool though and by all means do it on that basis but don't try to claim a scientific basis for it 🙂

Phil Wood make an ISO track hub - a double sided fixed hub for 6-bolt cogs. 120 mm OLN so a little wider than a normal front.

https://www.philwood.com/products/hubspgs/ISOtrackhubs.php

Have a look at trials motorcycles: 250- 300cc, 70kg ish , top speed in normal gearing = 50mph+

1 diddy disc up front. Probably down to competition rules than anything else, but they work.

[img] [/img]

maximusmountain - Member
clubber - based on what ive read its either double disc, 4 pot w/ 210 rotor or 2 pot with custom rotor and mount. Considering the tyres weight 1.6kg, the rims weight 1.1kg and thats the rotating mass

When you pull the brake on there's 60-100kg of you to stop also, with its CoG centred way more distant from the front hub.

EDIT the CoG isn't actually relevant.

There was a run of production z1's (can't remember what year) with double disc mounts. Seen them sell for £80 before. Bloody good forks too, open bath reliabilty and pretty stiff for the era.

Stoner - Member
Id get busy with a hacksaw, some carbon fibre & resin and a pair of deore front hubs

The disc sides of two drore hubs bonded together, and six long disc bolts running between the spokes and secured with nuts on the other side?

It's all very well having stupendous stopping power but don't forget the thing that actually stops you is the grip between the tyre & ground.

If the tyre/surface interface isn't good enough it's not going to matter how good the brakes are, you still won't stop well.

I'm circa 95-100kg at he moment in my stockinged feet, go out well kitted up on a bike probably weighing around 16kg (possibly more) and find 205 front & 180 rear discs using Hayes Strokers more than enough stopping power when pointing downhill.

nedrapier - Member
Have a look at trials motorcycles:
1 diddy disc up front. Probably down to competition rules than anything else, but they work.

There's no maximum permitted size for brake rotors but bigger = heavier of course, so it's down to the smallest that will do the job.

I'm circa 95-100kg at the moment in my stockinged feet

Pinky? In stockings?

#strangest

120kg using Hope Mono Minis with 183 mm rotors. I stop just fine. I think you'll be fine with something "normal".

* If it's just to see if you can build it then crack on. 🙂

years and years ago I bought a second hand Zascar which had some of those Bomber Z1s with the double disc mount fitted. Intriguing but never saw a brake or hub to match.

There was a run of production z1's (can't remember what year) with double disc mounts.

I had a pair!
Z1 Alloy, imported from Supergo in california in 1998.
Had "Formula" mounts on both legs - similar to IS, but slightly smaller bolt spacing, meant could only run a (single) Hope C2 as that was they only brake available with optional mounts.

Seen here, some years later:
[url= http://farm3.staticflickr.com/2409/2410263313_08924cc9b6_b.jp g" target="_blank">http://farm3.staticflickr.com/2409/2410263313_08924cc9b6_b.jp g"/> [/img][/url]

After some quick calculations I have found that actually I have ~250% more energy to lose with 36" wheels (5% increase with a rider on in linear terms at 20mph), so I think my requirement for dual discs isn't un-sensible when I could run dual 180's to dissipate the heat and reaction forces more evenly, and less funny things happening on the stanchions. The traction at the wheel isn't a concern considering the expected contact patch and weight transfer.

Yeah, yeah, you just want double discs because they'll look cool 🙂

I made this for a Brompton a while ago:

[img] [/img]

Perhaps a little bit overkill on a Brommie 😉

That is the absolutely most ridiculous thing I have ever seen. which hubs did you butcher? (look like hopes)

Oh, some basic physics - you don't have more energy to dissipate with a larger wheel, but the leverage ratio is worse - so to get the same braking force as a 180mm rotor on 26", you need a 250mm rotor on 36".

Might be a lot easier to use a custom Hope rotor and a fork with disc mounts higher up.

There's no maximum permitted size for brake rotors but bigger = heavier of course, so it's down to the smallest that will do the job.

OK, same as for push bikes then, except weight is less of an issue when you have an engine. So if a single 185mm rotor does fine stopping a 140kg - 160kg motorcycle and rider from 40 - 50mph, it'll probably work ok on a push bike with big wheels.

go on then ben, put the OP out of his misery, from what did you fab the dual rotor mount hub?

Wasn't a Hope - it was someone who made a prototype for BMX I think got the shell through BikeBiz, then hand to turn a custom axle.

i have a pair of Z1 bams with the dual disc brake mount but sadly not the right hand side caliper 🙁

This sounds ace!
Are you planning on trying to make it a thing of aesthetic beauty too?

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.

[img] [/img]

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]

[img] [/img]

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.