New bike build, hub gears & brakes, belt drive

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Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: New bike build, hub gears & brakes, belt drive

Post by Brucey »

it is as well to remember that belt drives were widely used before chains for many purposes, driving all kinds of industrial machines in the 19th century. Later they were used for motorcycles and features such as expanding belt drives to give variable gearing were certainly manufactured.

Whilst belts then were different to those available today, (many were repairable and comprised many links in fact) they were cheerfully abandoned in favour of chain drives for motorcycles and (AFAICT) were never popular for bicycles. I wonder if there are any lessons to be learned there?

The issues with chaincases concerning rear wheel removal and separation of the drive from the wheel etc are all soluble in a variety of ways. Even with chaincases as we know them today there is no need to remove the rear wheel unless the tyre is being changed (even then there are 'Dutch Pliers'); between tube repairs in situ, sealants, and linear tubes, there are plenty of workable methods.

The idea that belt drive will definitely help with the rear wheel in the event of a puncture may be mistaken; the requirements for both tensioning and alignment are more demanding than those for a chain, I would have said.

I'd love to see a practical and inexpensive belt drive but I'm not holding my breath.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
bobc
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Joined: 5 Apr 2012, 11:59am

Re: New bike build, hub gears & brakes, belt drive

Post by bobc »

thanks for the kind words above - OK a few words on various topics.... The SA 90mm drum and dyno hub - it brakes well (wouldn't want it to be much sharper considering that it stresses the front forks in a way they were not designed for) and the dyno seems very effective. But it's all a bit massive... the 70mm hub seems disproportionately less humungous (a colleague has one) but it is noticably less effective. He has 70mm drums front and rear. Now, the gearing & mechanical advantages of all the brake stuff on his bike is the same front as rear but the front seems much more effective as a stopper. Seems strange - the coefficients of friction & leverages don't change but the front wheel stops you & the rear just slows you down a bit. I've noticed this with all the rim brakes I ever had too. Is it because the cable run is shorter to the front? Do hydraulics have the same characteristics? Winding back a bit, the 90mm drum hub without a dyno does look considerably less enormous....
The belt I got was "isoran" from megadyne. I did request information from them about web tensile strength but got no answer; probably thought it not worth putting any effort into a £65 sale, + their strength appears to be less than I need. I've not been able to look for an upgrade yet, but I might go down to the drives and controls show at NEC next week; all the major suppliers will be there & I should be able to sort something out. That includes Gates, it will be interesting to see if they would supply a carbon reinforced industrial alternative to their own (megabucks) carbondrive.....TBH I don't see why not.
For now I'm a bit busy at work so it will probably be a few weeks before I make any real progress (I have to talk to the suppliers in work hours). So don't hold your breath waiting for "latest instalments". Meanwhile the old alfine11 bike is back in use - interesting to ride the steel frame and the ally frame + carbon forks back to back - the steel one gets my vote :)
Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: New bike build, hub gears & brakes, belt drive

Post by Brucey »

re the brakes; with a long cable a good deal of the force is gone before it gets to the brake, and more bends in the cable makes things worse, always. But then the ultimate braking power on the rear wheel is limited anyway; weight transfer sees to that. Hydraulics are better, power-wise; even with a smaller rear disc you can usually lock the rear with no difficulty.

The 70mm drums are not as powerful as the 90mm drums but.... they all need to bed in. Bedding in can take ages. Like about a year, if you don't use the brakes that much! I have well-bedded in 90mm drums on my present town bike and they are brilliant.

I wish you every good fortune tracking down a decent belt. As well as the strength I think you may need to have a worry about the stiffness, and recommended preload etc. I guess strength and stiffness should go hand in hand with any given reinforcing material.

I have a feeling that if you make a narrow belt stronger, the reinforcement plies need to be thicker, and that this may influence the minimum bend radius and perhaps even the fatigue life of the belt. So industrial belts are usually made wider if they need to be stiffer or stronger, which is much the easiest thing to do so far as the belt manufacturer is concerned.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
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breakwellmz
Posts: 1982
Joined: 8 May 2012, 9:33pm

Re: New bike build, hub gears & brakes, belt drive

Post by breakwellmz »

Quit happy with my Galvanised chain,probably too little "dry"motorcycle spray lube,simple home-made friction"tensioner",and the very occasional proper chain clean! :D
Is motorcycle cam belt material technology different again?
bobc
Posts: 495
Joined: 5 Apr 2012, 11:59am

Re: New bike build, hub gears & brakes, belt drive

Post by bobc »

Saw a bunch of toothed belt vendors at the "drives & controls" show today, the good news is that 4 or 5 claimed they could compete with gates & megadyne said they'd do me a replacement FOC from their "platinum" range ( which they pitch against gates' carbon jobs) Apparently some patent covering carbon reinforcement recently lapsed so there should be price competition in that sector starting now. There was a bit of interest expressed about the bike market, but I take that with a pinch of salt - reps & salesmen don't forge company strategy...
Anyway - I might get something to try in a couple of weeks.
I also spoke to dunlop and poggi that I can remember & maybe one or two others.
Generally - sounds optimistic - even Gates sounded positive about sourcing one of their industrial products to compete against their highly priced "bike specials" (not very convinced about that one....)
Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: New bike build, hub gears & brakes, belt drive

Post by Brucey »

I think you have done well to tap up as many belt makers as that 'in one fell swoop' as it were.

If you get any specifications for the belts I'd be interested to see them.

Are you looking only at belts to fit your new pulleys or are you looking at others too?

BTW is there an alternate approach to the possible alignment sensitivity issue? Gates do a special ridged belt for this, but as long as it isn't a mainstream thing, it'll be 'specialist' and a bit pricey.

Also- did you ever look at the belt used in the 'strida'? I wonder how that stacks up vs what you need? I guess it didn't see anywhere near the same load, being on a small wheeler.

cheers
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squeaker
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Joined: 12 Jan 2007, 11:43pm
Location: Sussex

Re: New bike build, hub gears & brakes, belt drive

Post by squeaker »

cycle tramp wrote:
bobc wrote:My motivation here, for the benefit of everybody, is to try to reduce that cost.


And i for one, am grateful. i've really enjoyed tuning into this thread, and following the build up of this bicycle, and the development of a home made belt drive system...

+1, big respect to bobc :D
"42"
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[XAP]Bob
Posts: 19793
Joined: 26 Sep 2008, 4:12pm

Re: New bike build, hub gears & brakes, belt drive

Post by [XAP]Bob »

Brucey wrote:I think you have done well to tap up as many belt makers as that 'in one fell swoop' as it were.

If you get any specifications for the belts I'd be interested to see them.

Are you looking only at belts to fit your new pulleys or are you looking at others too?

BTW is there an alternate approach to the possible alignment sensitivity issue? Gates do a special ridged belt for this, but as long as it isn't a mainstream thing, it'll be 'specialist' and a bit pricey.

Also- did you ever look at the belt used in the 'strida'? I wonder how that stacks up vs what you need? I guess it didn't see anywhere near the same load, being on a small wheeler.

cheers


Why a ridged belt rather than a flared "guard" either side of each sprocket?
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: New bike build, hub gears & brakes, belt drive

Post by Brucey »

[XAP]Bob wrote:

Why a ridged belt rather than a flared "guard" either side of each sprocket?


I can think of two possible reasons for this;

-if the installation width is limited and the strength/stiffness of the belt is also a limiting factor (rather than tooth engagement) then arguably a ridged belt gives a lighter/ stiffer/more compact installation than one installed with pulley flanges.

- possibly the ridged belt tolerates a little mud better because it can be squeezed out sideways more easily.

but maybe I'm thinking about this the wrong way...?

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
bobc
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Joined: 5 Apr 2012, 11:59am

Re: New bike build, hub gears & brakes, belt drive

Post by bobc »

I think you're right on that one Brucey. Answering your questions above:
No never looked at the strida belt; Yes I want to use same pulleys, so want same HTD14mm section (a reason to steer clear of gates...)
I'll relay specs as and when I get 'em, I believe the "platinum" megadyne is nearly twice as strong as the "isoran" (what i have already)so that should be fine, for me at any rate - might not be reliable for Chris Hoy!
I was talking about 5000N (+) on a 10mm wide web, whereas they, of course, wanted to talk about power, revs and diameters; no matter, it should all come to the same. That would give big fat me an FOS of 2.5 or so.
Note that the existing belt did not fail, just stretched enough for me to notice, then it un-shipped; it was OK afterwards for 15 miles home.
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[XAP]Bob
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Re: New bike build, hub gears & brakes, belt drive

Post by [XAP]Bob »

No reason not to have "mud holes" under the teeth as in bobc's sprockets - but yes, I can see 'foreign' objects being an issue...
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
bobc
Posts: 495
Joined: 5 Apr 2012, 11:59am

Re: New bike build, hub gears & brakes, belt drive

Post by bobc »

Been a while & not much happened with this bike... Frankly, my old alfine 11 bike is going so well I've no great rush and I'm sort of changing my mind about what I want....
At the front, I like the drum brake but the dyno is a big white elephant for me - I use the bike in daylight, why would I want to cart 1/2 a kilo of iron everywhere....
At the back, I'm going off the SA 8spd... I'm an old git & the 300% range is an issue - there's quite a steep hill on my commute & I'd either be pushing or straining. Plus my mate has one & he's already had to change its innards (highest ratio stage actually wore out!!!). So I'm thinking to hell with it - buy a rohloff with a disc :). Evans are flogging a rohloff for about 800notes, but it's QR & 32 hole, still £800 sounds not too bad...
Nice to have choices :)
LollyKat
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Location: Scotland

Re: New bike build, hub gears & brakes, belt drive

Post by LollyKat »

bobc wrote: Evans are flogging a rohloff for about 800notes, but it's QR & 32 hole, still £800 sounds not too bad...

About 870, actually, and it doesn't include the shifter.
bobc
Posts: 495
Joined: 5 Apr 2012, 11:59am

Re: New bike build, hub gears & brakes, belt drive

Post by bobc »

I was talking about this
http://www.evanscycles.com/products/roh ... b-ec044936
they want £70 more for the one with nuts& bolts
http://www.evanscycles.com/products/roh ... b-ec044934
Think I'll wait for what I want.....
bobc
Posts: 495
Joined: 5 Apr 2012, 11:59am

Re: New bike build, hub gears & brakes, belt drive

Post by bobc »

More thoughts on this old project: I will clearly die of old age before I get anything sensible out of the various toothed belt salespeople... but Gates do put reasonable data in their on-line data tables. I've been comparing their glassfibre reinforced belts with their carbon ones - the carbon are approx. 2.5x as strong in tensile strength. This accords reasonably with my experience; with quite a small chainring, when I stood on the pedals I put too much tension on a fibreglass belt (albeit somebody else's) so a carbon copy would have a factor of safety of about 2.5, which all seems reasonable.
The belt length I went for last time, 1288mm, is not very widely available as a standard size in 14mm pitch belt, but 1400mm is. The upshot is, if I design for 1400mm belt I end up with bigger chainrings and sprockets, but this is all good, it reduces belt tension, improves tracking and efficiency and puts more teeth in mesh.
It I look at the rohloff speedhub now; the gear range on this goes from "up a little bit" in top down to "down by about 4:1" in bottom. This is very different from the sturmey archer 8speed which only geared up. So I need a pulley ratio from ring to sprocket of over 3:1. A 1400mm belt works great at 60:18 and an 18tooth sprocket is just about big enough to avoid size derating, gives me nearly 9 teeth in mesh (avoiding derating which starts at 6) and works nicely as a "clamp- on" addition to a standard 13tooth rohloff sprocket.
So I've started putting bits together. I'll get a brake disc lasered (£8 is lots less than a rohloff special....) & start making a caliper bracket to sit in the left side of the rear triangle. I'll get the belt sprocket parts lasered & put that together on the 13tooth sprocket ( that will be about £30 for bits + £23 for the 13 tooth sprocket, minus whatever ebay gets me for the 16t that comes with the hub).
I'll certainly stick with the 14mm pitch belt but I don't know yet whether I'll get a carbon one or an improved non-carbon one; whichever I do, I will have much more choice by moving to 1400mm length rather than the 1288mm I started with.
I'll post pictures when the parts start arriving. I've already sold the dynohub wheel & will ebay the sturmey archer 8speed wheel shortly.
TTFN
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