Author Topic: Brompton builder  (Read 3759 times)

Re: Brompton builder
« Reply #50 on: November 08, 2018, 02:12:02 pm »
The biggest faff is fitting the chain tensioner, which is always a filthy-fingers job.  On IGH Bromptons the anti-rotation tab washers have to go the right way up...they sort of fit the wrong way up, so it's easy to get it wrong.  British engineering prowess.
Never tell me the odds.

whosatthewheel

Re: Brompton builder
« Reply #51 on: November 08, 2018, 02:14:39 pm »
The biggest faff is fitting the chain tensioner, which is always a filthy-fingers job.  On IGH Bromptons the anti-rotation tab washers have to go the right way up...they sort of fit the wrong way up, so it's easy to get it wrong.  British engineering prowess.

Why they didn't use a hanger like "normal bikes"?

Re: Brompton builder
« Reply #52 on: November 08, 2018, 02:21:11 pm »
The trick is to not put the tensioner arm into the chain until after you’ve bolted it on.

[quote author=whosatthewheel link=topic=110101.msg2340228#msg2340228 date=
Taking into account everything, including the fact that it's easier to fiw a puncture on a 2 speed than it is on a 3 speed, I cam to the conclusion that 2 speed is the best compromise for me.
There will be a couple of times per year when I will regret that choice, but I will probably regret more often having the 3 speeder
[/quote]

The upgrade path from two speed to six speed is fairly straightforward, so worst case scenario you can do that.

Kim

  • Timelord
Re: Brompton builder
« Reply #53 on: November 08, 2018, 04:40:39 pm »
The trick is to not put the tensioner arm into the chain until after you’ve bolted it on.

Seconded.

The other gotcha is not trapping an extra half-link of chain between the sprocket and the jockey wheel, but I assume that's a Kinetics 8-speed specific issue.
To ride the Windcheetah, first, you must embrace the cantilever...

SoreTween

  • Most of me survived the Pennine Bridleway.
Re: Brompton builder
« Reply #54 on: November 11, 2018, 09:49:48 am »
The SA8 hub steps up through two epicyclics most of the time and three of them in top gear. It isn't a particularly efficient hub gear for losses under power, unlike a three speed hub. How well it runs while coasting is much less important.
I bought a 2 speed always intending to go kinetics 8 in a second year cyclescheme. That's the least wasteful in discarded parts my legs can cope with. This is making me reconsider, having the direct gear at the bottom feels wrong, it would annoy me. SA5 (assuming it fits) or Alfine 8 are back on the table. No rush to decide, changing jobs in the new year which will rule cycle commuting out :-(
2019 targets: TINAT 160 rough
There is only one infinite resource in this universe; human stupidity.

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton builder
« Reply #55 on: November 11, 2018, 10:04:49 am »
To be fair, the SA8 has a lot of positives. It is lighter and cheaper than every other complex gear hub and it is most efficient when you need every watt to be useful; climbing with no easier gear available. It just isn't a 'performance' hub. A Brompton isn't a performance bike either but it is eminently practical and useful, so they are a good match for some folk.

I'd still be happy enough to use a SA8 (or a Brommie) on a brevet again while understanding that there are easier ways to get round. I ride a trike, tandem or other machines on some brevets because it is more interesting/ fun than just bombing around for the least effort expended.

The Alfine 8 isn't a particularly efficient hub either; driving up and down through sequential epicyclics. It is closer to bombproof and shifts nicely, though heavier and more expensive.
Wheel meet again, don't know where, don't know when...

Kim

  • Timelord
Re: Brompton builder
« Reply #56 on: November 11, 2018, 01:09:39 pm »
To be fair, the SA8 has a lot of positives. It is lighter and cheaper than every other complex gear hub and it is most efficient when you need every watt to be useful; climbing with no easier gear available. It just isn't a 'performance' hub. A Brompton isn't a performance bike either but it is eminently practical and useful, so they are a good match for some folk.

+1

I reckon they're well suited to each other.  For me the Brompton is a workhorse for short urban journeys and occasional mobilty aid, which I sometimes do a Bike Ride on (mainly because the foldingness means I can have a bike with me when I otherwise wouldn't).  The SA8 was the most elegant way of giving it the required bottom gear to handle my knee flare-ups, and it does that well.

The unconventional only-gearing-up approach is designed to sidestep the issue of small-wheeled bikes needing awkwardly large chainrings.
To ride the Windcheetah, first, you must embrace the cantilever...

SoreTween

  • Most of me survived the Pennine Bridleway.
Re: Brompton builder
« Reply #57 on: November 11, 2018, 03:56:18 pm »
The unconventional only-gearing-up approach is designed to sidestep the issue of small-wheeled bikes needing awkwardly large chainrings.
Ah yes, I see.  Thank you both for the education.
2019 targets: TINAT 160 rough
There is only one infinite resource in this universe; human stupidity.

whosatthewheel

Re: Brompton builder
« Reply #58 on: November 13, 2018, 03:57:15 pm »
The Cyclescheme voucher arrived early, so Saturday I went to place my order... S2L  all white...  :thumbsup:

SHould take up to 12 weeks, apparently...  :o

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton builder
« Reply #59 on: November 14, 2018, 09:41:19 am »
The biggest faff is fitting the chain tensioner, which is always a filthy-fingers job.  On IGH Bromptons the anti-rotation tab washers have to go the right way up...they sort of fit the wrong way up, so it's easy to get it wrong.  British engineering prowess.

Why they didn't use a hanger like "normal bikes"?

Because it would make even harder to remove the rear wheel if the chain tensioner is still bolted to the frame. The Brompton has slightly rear-facing dropouts, so that the tyre clears the chainstay bridge as it drops out. The bridge is so close to the tyre because the bridge stabilises the front of the rear mudguard without using a bolt. That rearward movement as the wheel is removed is the wrong direction for the sprocket to clear the top pulley.

I don't understand why people find the chain tensioner to be difficult to deal with. I remove/ fit the chain tensioner from/ to the frame one-handed with the chain correctly running around the pulleys before the tensioner is fitted to the bike. No need to directly touch the chain at all.

All white Bromptons (with blue decals?) used to denote 'demonstrators'. I'm not sure if they were influenced by Moulton's 'works' specials being painted white.
Wheel meet again, don't know where, don't know when...