Search found 157 matches

by StephenW
16 Feb 2018, 10:29am
Forum: Bikes & Bits – Technical section
Topic: Which chain Guard?
Replies: 4
Views: 594

Re: Which chain Guard?

Hello Belgiangoth

I have this chain case:

https://www.dutchbikebits.com/mudguards ... -chaincase

I find it very worthwhile. When I look at the places where it is dirty, not all of them are in areas which would be covered by a hockey-stick chain guard.

It clamps around the chainstay, so won't affect chainline. If it doesn't quite fit you can carve pieces off it with a stanley knife, or bend the bracket a bit.

Do you use chain tugs? Perhaps that would make setting the chain tension easy. Alternatively, if you use Sheldon Brown's method for setting the chain tension, it should be possible to find the right sideways pressure to get chain tension just right, even without being able to see or touch the chain.
by StephenW
18 Jan 2018, 10:21pm
Forum: Non-standard, Human Powered Vehicles
Topic: Why are recumbents so rare?
Replies: 126
Views: 12468

Re: Why are recumbents so rare?

I have a Dutch friend who owns a Zephyr Lowracer. Yesterday I asked him why he didn't bring it with him when he moved to the UK. He replied: "Because I want to live!" This friend rides an upright to work every day here. He also commented that even in the Netherlands he has some safety concerns in certain situations with the lowracer, for example if there is a small hedge between the cycle path and road, he might not be seen by drivers turning into the side road.

I think it is reasonable to say that recumbents are perceived as being much more dangerous in traffic than upright bikes. (As I said before, whether they actually are or not is a separate matter).

If a Ford Fiesta does a good enough job at everything average Joe wants to do in a car, why would he want a BMW Series 5?


Well, the most popular car in Britain is the Ford Fiesta! Some people are car enthusiasts, and some are bike enthusiasts, but most are neither. Most people just want something that does a decent enough job. Also, it seems that you are saying that a recumbent is a pure upgrade on an upright bike, whereas I would see it as a different thing, with its own different set of compromises. To me it's not so much like Ford Fiestas and BMWs, more like skiing and snowboarding.

People don't cycle in general because it's weird and different (the "dangerous" is a misconception used to rationalise, I suspect).


I disagree! If people repeatedly say that they think cycling is dangerous, I believe them! I don't think people consider cycling to be weird. Lots of people have a bicycle languishing in a shed. It's riding in traffic that people find weird or unnatural, especially riding in a "vehicular" fashion.
by StephenW
16 Jan 2018, 10:46pm
Forum: Non-standard, Human Powered Vehicles
Topic: Why are recumbents so rare?
Replies: 126
Views: 12468

Re: Why are recumbents so rare?

Hello Tangled Metal

I bought a very good second hand recumbent for a good price in a village a few miles away from me. (It was on ebay).

I'm not in London or SE.

If you keep your eyes peeled, hopefully something will turn up locally.

Some recumbents have racks for conventional panniers. Others use special recumbent-specific panniers.
by StephenW
16 Jan 2018, 10:42pm
Forum: Non-standard, Human Powered Vehicles
Topic: Why are recumbents so rare?
Replies: 126
Views: 12468

Re: Why are recumbents so rare?

Hello all

I suppose I was really making two points:

1. People won't ride recumbents if they perceive them to be dangerous in traffic.
2. As enthusiasts, we shouldn't misunderstand what most people want from a bike.

Personally I find the experience of riding in busy traffic more unpleasant on the recumbent than upright.

"Is it safe?" is a question I am frequently asked. It is people's perception of danger that matters - the actual level of risk is neither here nor there.

If recumbents are to become common, I think a significant increase in subjective safety is necessary (e.g. through Dutch-style infrastructure).

If a roadster does a good enough job at everything average Joe wants to do on a bike, why would he want a recumbent? I'm talking about people who are not "proper cyclists", and have no intention of becoming one. They just want an easy way of making short trips around town.

Regarding pockets, I've twice dropped my phone on the road! Of course, on longer journeys it is no problem to put things in a bag or deliberately wear something with zipped pockets, but on short trips this is an inconvenience.

Regarding shoes, I find that being clipped in makes a far greater difference on the recumbent than on the upright. (I have particularly high BB).

There's recumbents and there's recumbents.


Very true! My experience is limited to SWB bikes.
by StephenW
13 Jan 2018, 2:11pm
Forum: Does anyone know … ?
Topic: Fast rolling tires? 26 inch
Replies: 35
Views: 7517

Re: Fast rolling tires? 26 inch

Schwalbe Kojaks are described by many people as being quite fast. But on bicyclerollingresistance.com they get a very poor rating.

What's going on?

Are people being deceived by their perceptions? (more vibration=faster)

Are the bicyclerollingresistance.com tests simply wrong?

Do the bicyclerollingresistance.com tests not adequately reflect the real conditions of using a tyre?



https://www.bicyclerollingresistance.com/tour-reviews/schwalbe-kojak-2017
by StephenW
13 Jan 2018, 2:04pm
Forum: Non-standard, Human Powered Vehicles
Topic: Why are recumbents so rare?
Replies: 126
Views: 12468

Re: Why are recumbents so rare?

I do think that the presence of busy motor traffic has a big influence on who cycles, where they cycle, and what kind of bike they ride. If people perceive riding a recumbent in traffic to be too dangerous they won't do it, even if there is no hard evidence for this. (We on this forum think it's fine, but then we are the people who have chosen to do it!).

I'm sure the UCI ban has some sort of effect too.

But even if we got rid of these deterrents (i.e. if we had Dutch-style road design and racing rules changed), and allowed some time to adapt, I don't think anything like the majority of bikes would be recumbents. My reason for saying this is that I think all that most people want to do on a bike is make short trips around town (up to around 4 or 5 miles), and perhaps occasionally go for a gentle potter on a sunny Sunday afternoon. A roadster does this job quite well, whereas in this application a recumbent has some disadvantages:

- things can fall out your pockets
- can't wear certain clothes
- works better with special shoes
-can't carry rucksack (although you could put a basket on)
etc...

But clearly as you start to want to go further (and faster) the advantages of the recumbent increase.

I could imagine that maybe 15% of bikes could be recumbents, if we had Dutch-style infrastructure, different racing rules, and some time to adapt.
by StephenW
29 Oct 2017, 7:36pm
Forum: Non-standard, Human Powered Vehicles
Topic: Recumbent Steering - What's going on?
Replies: 41
Views: 3791

Re: Recumbent Steering - What's going on?

I can ride no-hands on my Metabike, but I need to be going quite a bit faster than on an upright and it takes a lot of concentration.

Initially I found "superman" type handlebars much more intuitive and similar to an upright bike. However, with a bit of practice tiller bars are also fine.
by StephenW
29 Oct 2017, 7:16pm
Forum: Non-standard, Human Powered Vehicles
Topic: Avoiding power idler by using Alfine hub gear
Replies: 20
Views: 3627

Re: Avoiding power idler by using Alfine hub gear

Hi all

I realised that the boom had been cut down by a previous owner. Because I am quite tall, I have the boom extended fairly far out. This meant that not enough of the boom was inside the frame, causing undue flex. I was able to buy a spare full length boom from someone on BROL, and this has fixed the problem. The old boom had been slightly squashed out of shape :shock: Oops!

I've been thinking a bit about two mysteries: firstly, Jan Heine's "planing" idea, meaning that a more flexible frame seems to climb hills better, and secondly that recumbents supposedly don't climb hills well. Are these two things related? I have an idea that they might be.

My idea is that the abdominal muscles contribute quite a lot to cycling. A flexible upright frame might allow the hips to move sideways relative to the pedals and the abdominal muscles to be used more effectively. Since the hips are more fixed in position on a recumbent, it is harder to use the core muscles effectively.

According to Heine, flexible chainstays are not good. It is a flexible top tube and seat stays that are desirable. This fits with my experience - I don't think sponginess in the drivetrain is beneficial at all. Even a relatively flexible upright is likely to be stiffer than many recumbents in this regard I suspect.

What I think would be best, is a drivetrain which is as stiff as possible, combined with the necessary sideways flex to allow the core muscles to contribute to the effort of pedaling. I can think of three ways this might be achieved:
1. Front wheel drive. The front part of the frame, as far back as the power idler, can be made very stiff. Rearwards from this point, the frame can be made more flexible.
2. Stick bike with no idler. In this case, the chain is loading the frame in almost pure compression. This gives a stiff drivetrain. The stick could have a certain amount of sideways flex.
3. A seat which consists of two parts: a back which is firmly fixed, and a bottom part which is flexibly mounted so that the hips can move a bit. Perhaps it could be able to swivel, with a spring pulling it back to the centre.

What do you think?
by StephenW
28 Sep 2017, 10:03pm
Forum: Campaigning & Public Policy
Topic: You can forget about your Dutch-style cycling facilities
Replies: 85
Views: 7154

Re: You can forget about your Dutch-style cycling facilities

Here is an interesting blog post about Stevenage, written by someone who designs roads for a living and has done a bit of cycling in the Netherlands.

http://therantyhighwayman.blogspot.co.u ... ished.html
by StephenW
28 Sep 2017, 9:47pm
Forum: Non-standard, Human Powered Vehicles
Topic: Avoiding power idler by using Alfine hub gear
Replies: 20
Views: 3627

Re: Avoiding power idler by using Alfine hub gear

Hello all

Thanks for the interesting responses. I'll reply to a few points, and then add some new thoughts.

Replies

[XAP]Bob: I was thinking of vertical bending, rather than horizontal bending or torsion. I'm much more aware of vertical movement than the other two, although I'm sure they do happen too. I know the Raptobike has a reputation for a direct feeling through the drivetrain. Do you think this directness translates to hill-climbing ability, or is it more just a nice thing to have?

Upwrong: I have the Terracycle toothed idler. A previous owner must have fitted it. Have you ridden other similar LWB bikes to your Stratus XP which do have a power idler? Did you notice a difference?

Brucey: Your mid-drive sounds very interesting. How did you tension the front chain? Perhaps this kind of mid-drive could also be used on a FWD or even a FWD tandem?! I guess that this is something that the frame really needs to be designed around from the start.

I hadn't thought about the effect of the chain sagging. Do you think that a "clutch" rear derailleur could be useful in this case? I was also musing about some kind of floating chain support, where the chain runs between two wide, smooth pulleys. These are allowed to move vertically, but are held at their height by friction. If the amount of friction is correct, the device will stay in the same place when it is supporting the weight of the chain, but will move to a new position when the rider selects a different gear and the chain needs to be in a different position. I haven't yet done the sums to see if the force after a gear change is significantly smaller than the force from the weight of the chain.

I haven't fully digested what you are saying about toothed idlers and forces, but I will give it further thought.

New Stuff

I went out for a ride on Sunday afternoon and removed the idler halfway around. When I took the idler off, I flew along! It was great! There may be a psychological advantage from having a quiet bike (and a psychological advantage is also not to be sneezed at), but I am certain that there was a genuine increase in efficiency. I can think of two reasons for this:

1. Friction resulting from idler.
2. Reduction in frame flex due to forces from chain being more aligned with frame tubes.

I feel that no. 2 is quite important.

In this instance it seems that the losses from the chain sagging were less than the losses which were avoided by removing the idler.

Consider this M5 m-racer. I have never ridden this bike, but I find it hard to imagine that it would climb well in a small chainring. The load from the chain is not aligned with the direction of the frame tubes, meaning that they are loaded in bending rather than compression.

m5.jpg
m5.jpg (43.86 KiB) Viewed 1514 times


Consider this "stick bike". It seems to me that such a bike would be ideal to run without an idler - the "stick" would be under almost pure compression, no vertical bending forces. Unfortunately, by the looks of things, the chain might rub on the chain stay in certain gears, due to the dropouts. I suppose that on a steel frame these could be modified. I think some kind of cover for the chain as it passes under the seat and the rider's right leg could be a good idea, also to stop the chain flailing around when riding over bumps. This could be a piece of square plastic drainpipe.

giro26-big.jpg
by StephenW
18 Sep 2017, 10:21pm
Forum: Bikes & Bits – Technical section
Topic: Cycling as a whole; losing the plot...?
Replies: 512
Views: 21665

Re: Cycling as a whole; losing the plot...?

This is a slightly different angle to Brucey's original point, but perhaps part of the reason this "progress" is frustrating, is that so much effort is going on things which are relatively unimportant (e.g. adding another sprocket), when there are other areas with significant potential for improvement. If bike design was already nearly perfect in every other way, then we wouldn't be so bothered about all this faff for just one more sprocket.
by StephenW
18 Sep 2017, 9:56pm
Forum: Non-standard, Human Powered Vehicles
Topic: Avoiding power idler by using Alfine hub gear
Replies: 20
Views: 3627

Re: Avoiding power idler by using Alfine hub gear

Thanks for the replies.

Hercule: Yes the range of the 11 speed Alfine is a bit less than I had thought. Or rather, my current gear range is a bit more than I thought. I use all the gears I have.

UpWrong: I found an old thread on BROL, where someone from Bacchetta was suggesting losses of 1-2% for an idler. I'm not sure of the losses in the derailleur jockey wheels, but I guess it's not much. So from a strict efficiency point of view, I'm sure you are right. However, if removing the idler increased the stiffness through the drivetrain, this could be beneficial, especially for hill climbing. This is harder to quantify I think.

I had a bit of a read around. It seems there have been some recumbents without power idlers. People said that they were nice and smooth and quiet.

I do think that stiffness through the drivetrain is important. I don't believe that much energy is being converted into heat through flexing. (Although if it was, you probably wouldn't know, due to good thermal conductivity of the frame and good heat transfer through forced convection). I think that the problem with flex is rather that the feet have to make additional movements which are not contributing to the propulsion of the bike, and the flex also shortens the useful power stroke.

Anyway, I think the effect of chainring size on flex is important, and doesn't seem to get a lot of attention. Using the 22 tooth chainring, with 152 mm cranks, the bike feels noticeably noodly. (I am tall and have the boom extended out a long way). Perhaps there would be value in using one of the cassettes with a humongous 42 tooth sprocket, in order to give low gearing without requiring small chainrings. (Hub gear/hybrid gearing would also give low gears without small chainrings).
by StephenW
22 Aug 2017, 10:15pm
Forum: Non-standard, Human Powered Vehicles
Topic: Avoiding power idler by using Alfine hub gear
Replies: 20
Views: 3627

Avoiding power idler by using Alfine hub gear

Hello all

I have a Metabike, which I enjoy riding. It currently has 3*10 derailleur gears. The idler is quite noisy, because it only bends the chain through a small angle. I have discovered that it is possible to remove the idler and ride the bike like that. Unfortunately in some of the gears the chain rubs on the seat bracket, but in the gears where it does work, it is nice and smooth and quiet. It feels more efficient and less flexy, although that might just be psychological, as it makes no noise. (The less flexy part comes from the fact that the direction of the chain is more in line with the frame, thus causing less of a bending load on the frame).

I've been thinking that if I get a hub gear, I could run it without the power idler and still have plenty of gears. I would continue to use a return idler, but would mount it in such a way that it can be moved, so that it doubles as a chain tensioner. Perhaps the lower efficiency of the hub gear will be compensated for by removing the power idler? Also, using a hub gear means that it is possible to use only a largish chainring, reducing chain tension and frame flex compared to a small chainring.

The final part of my plan would be to put the chain inside some kind of conduit. Not the kind of chain tube which rubs on the chain, but a tube which is larger than the chain, and is firmly mounted to the frame. Like a chaincase on a roadster. This would keep both the chain and my legs/trousers clean. The chain would slap against the inside of the tube over bumps, but I don't mind this too much.

What do people think? Has someone done something like this before?

Thanks
Stephen
by StephenW
5 Apr 2017, 9:50pm
Forum: Bikes & Bits – Technical section
Topic: IGH lubrication; a smoking gun.
Replies: 163
Views: 22322

Re: IGH lubrication; a smoking gun.

Mystery solved! As you said might happen, I didn't manage to get all the white spirit out of the hub. It had collected in a puddle at the bottom and had washed the grease off the drag spring, making it noisy. (I suppose it must have been making the same noise in gear 1, but I didn't notice because that gear is a bit noisy anyway).

I wiped out the white spirit and added a dollop of grease, and it is running nice and quietly now.

For future reference, what would you recommend for cleaning out the hub? Methylated spirits? Diesel?

Thanks for all your wise advice Master Oogway, I mean Brucey :)
by StephenW
28 Mar 2017, 7:23pm
Forum: Bikes & Bits – Technical section
Topic: wide tyres; is there any limit in sight?
Replies: 29
Views: 1964

Re: wide tyres; is there any limit in sight?

This is interesting. I have been thinking about this a bit.

One of the main reasons given against fat tyres is aerodynamics. Wheel covers to hide the spokes exist, but as far as I know they are only as wide as the rim. Would it be possible to make a wheel cover which is as wide as the tyre? There could be a flexible skirt joining the tyre to the wheel cover, so that the tyre is able to bulge over bumps without digging into the wheel cover. This would give a smooth transition from the tyre to the cover, to avoid disrupting the air flow. I am thinking of an old inner tube for the skirt, cut in half vertically to give one half for each side. Perhaps some plastic blocks could be glued to the rim, and the cover screwed onto these. Of course, this would all only work with disc or hub brakes.

From what I gather, wheel covers or disc wheels would not be recommended for the front wheel, due to problems with side winds.