Search found 210 matches

by Chris Jeggo
8 Apr 2021, 10:29pm
Forum: Does anyone know … ?
Topic: Cracked carbon frame
Replies: 53
Views: 2110

Re: Cracked carbon frame

Has anyone tried a carbon fibre repair like this on a metal frame? A clubmate of mine suffered a broken seat tube of a 531DB frame, fitted some sort of metal sleeve round it and glued it all together with araldite. It doesn't look pretty, but it's still holding together many decades later. (He's the last of the small spenders.)
by Chris Jeggo
8 Apr 2021, 10:16pm
Forum: Does anyone know … ?
Topic: Tudor Sports jerseys/jackets sizes?
Replies: 6
Views: 267

Re: Tudor Sports jerseys/jackets sizes?

Agreed, they're a bit on the large side. I think they're a bit bigger than they used to be (a good many years ago), as you might expect, young cyclists being taller than old ones on average.
by Chris Jeggo
8 Apr 2021, 10:02pm
Forum: Does anyone know … ?
Topic: Strange items
Replies: 19
Views: 823

Re: Strange items

I'm white and graduated, but I don't rule anywhere.
by Chris Jeggo
5 Apr 2021, 11:58am
Forum: Does anyone know … ?
Topic: Superwheel - how does this work ?
Replies: 71
Views: 3646

Re: Superwheel - how does this work ?

jb wrote: 5 Apr 2021, 11:36am Drop a perpetual motion topic into any forum and you have a perpetual thread of infinite length - - -
:lol:
by Chris Jeggo
24 Mar 2021, 9:54pm
Forum: Fun & Games
Topic: English Language - what "Does your head in" ??
Replies: 970
Views: 37675

Re: English Language - what "Does your head in" ??

Bmblbzzz wrote:If you're referring to "CD's" .....

"GP's" could be quite confusing.
by Chris Jeggo
23 Mar 2021, 6:00pm
Forum: Bikes & Bits – Technical section
Topic: Best wishes for Brucey
Replies: 400
Views: 23842

Re: Best wishes for Brucey

I just got back from an afternoon on the bike enjoying the sunshine to be confronted by this terrible news. Get well soon, Brucey, we all miss you.
by Chris Jeggo
17 Mar 2021, 12:27am
Forum: Does anyone know … ?
Topic: Poyner's of Wolverhampton
Replies: 32
Views: 16621

Re: Poyner's of Wolverhampton

Fred Poyner is mentioned on this Wolverhampton history webpage.
by Chris Jeggo
16 Mar 2021, 1:15pm
Forum: Does anyone know … ?
Topic: Superwheel - how does this work ?
Replies: 71
Views: 3646

Re: Superwheel - how does this work ?

I have just received the Spring 'Arrivee' magazine from Audax UK and read a short piece about this device.

Yes, it sounds very like a perpetual motion machine.

Brucey wrote:Another way of looking at it is that if the claims were true, there would have to be at least 30% losses in a standard bike + rider that disappear once the gadget is used. There are only three places where such losses might occur;

1) in a standard transmission
2) in the way that a standard bike handles the bumps in the road
3) in the way that the human machine converts perceived effort to watts of pedal force

There are no claims for 3) ; no mention of any difference in pedalling, except that it is 'less effort'. Re 1) standard transmissions are measurably 90-95% efficient, so there is no scope for a large change in efficiency there. Which just leaves 2). If anything I'd expect a load of extra pivots in the rear wheel and a non-concentric rotation to absorb energy rather than dish it out somehow.

If there really was an effect of any kind (leave alone that magnitude) it ought to be easy to observe and measure.

cheers


Totally agree.

1) The only part of a standard transmission that this device alters is between driven sprocket and wheel rim, which I reckon is so close to 100% efficient that it is not worth the effort of trying to measure or calculate it.

2) This device may deliver the benefits of suspension over bumpy roads, but no more than a well designed dedicated suspension system.

3) It is possible that temporary energy storage in springs might produce ergonomic advantages similar to those (unproven) of non-circular chainrings. I road tested the prototype Deal Drive automatic transmission for bicycles for the CTC in 1983. Its complicated expanding/contracting 'chainwheel' contained springs which sometimes produced disconcerting effects when pedalling.

Let's spend no more time in a blind alley.
by Chris Jeggo
16 Mar 2021, 11:23am
Forum: Bikes & Bits – Technical section
Topic: Using smaller chainrings on a road double for touring
Replies: 31
Views: 1467

Re: Using smaller chainrings on a road double for touring

Some MTB double FDs cope better with road bike chain lines than others, so it's a good idea to check what finally limits inward motion of the cage.
by Chris Jeggo
15 Mar 2021, 7:06pm
Forum: Bikes & Bits – Technical section
Topic: Unable to remove HT2 bottom bracket in carbon frame
Replies: 66
Views: 1958

Re: Unable to remove HT2 bottom bracket in carbon frame

You guys are looking at clocks from the outside ... :D
by Chris Jeggo
15 Feb 2021, 11:37am
Forum: Bikes & Bits – Technical section
Topic: Deore 12 speed drivetrain review
Replies: 34
Views: 1056

Re: Deore 12 speed drivetrain review

mikeymo wrote:
Chris Jeggo wrote:
mikeymo wrote:
One advantage of my 9 x 3 ....


It's slightly better than that ....


.... As far as I can measure the middle chainring and sprocket 5 are dead in line, on a 45 mm chainline. So the inner chainring lines up with sprocket 7, and the outer chainring with sprocket 3 (or the other way round, depending on what numbers you assign to the sprockets).....


Your 9 x 3 set-up sounds pretty similar to mine.
by Chris Jeggo
15 Feb 2021, 10:54am
Forum: Bikes & Bits – Technical section
Topic: Deore 12 speed drivetrain review
Replies: 34
Views: 1056

Re: Deore 12 speed drivetrain review

mikeymo wrote:
One advantage of my 9 x 3 (well, any triple I suppose), is that there are 3 chain positions where the chain-line is pretty much dead straight. And if I make frequent use of the front derailleur there won't ever be a particularly bad chain-line.


It's slightly better than that because inter-chainring spacing is significantly larger than cassette inter-sprocket spacing. If the middle ring lines up exactly with one sprocket then the outer ring will be within a gnat's whotsit of aligned with the next two sprockets, and likewise for the inner ring.
by Chris Jeggo
14 Feb 2021, 12:29pm
Forum: Bikes & Bits – Technical section
Topic: Deore 12 speed drivetrain review
Replies: 34
Views: 1056

Re: Deore 12 speed drivetrain review

One chain per 500km; that would be 18 chains per year for my mileage, £450! More than £1 per day, just for chains. I am not going to bother trying to compare fettling time to riding time for that bike.