Search found 495 matches

by bobc
29 May 2017, 11:23am
Forum: Bikes & Bits – Technical section
Topic: Disc brake fitting
Replies: 13
Views: 2548

Re: Disc brake fitting

Be very thankful you found this in safe circumstances. Potentially lethal manufacturing error by the sound of it.
Hopping mad is well understated....
by bobc
26 May 2017, 12:17pm
Forum: Bikes & Bits – Technical section
Topic: Raleigh strada 4 belt drive problems
Replies: 6
Views: 2007

Re: Raleigh strada 4 belt drive problems

My "belt drive" experience has been overwhelmingly positive, but not much help seeing as I made all the parts except the belt myself.
I have a colleague at work who has run a gates "centretrack" where the belt has failed after about 1000miles, my "flanged" homebrew one still looks and works good as new after 12k miles. I'm pretty heavy with suspect knees so I probably give it average grief....
by bobc
26 May 2017, 12:09pm
Forum: Bikes & Bits – Technical section
Topic: What's the term for an e-bike drive from the rack?
Replies: 10
Views: 2352

Re: What's the term for an e-bike drive from the rack?

I don't think you'll find it.
I've made a few of these but all homebrews.
Maybe you could look for "friction drive" - sounds awful but actually works OK and should be cheapest possible solution. Knobbly tyres are a nono though.
by bobc
18 May 2017, 3:15pm
Forum: Bikes & Bits – Technical section
Topic: Supercommuter?
Replies: 121
Views: 24856

Re: Supercommuter?

Seems a slightly odd attitude to the ebikes
if the electrics fail - it's still a bike; pedal on dude :)
the big hub issue: a legal power ebike will have a hub only slightly larger (if at all) than an IGH or a dynohub. The old nuvinci IGH weighed in at over 4kg for the hub alone & might well be heavier than most legal hub motors. Spoke angles are kept sane by going down to 2cross or 1cross like you would with IGH or dynohub.
A 10kg monster hub would have been considerably over the 250W average limit, many of these things are 3kW average(!)
I've currently lent my ebike to an ex colleague who is "waiting for treatment" for a properly damaged knee. He is thereby now mobile again (has got his life back). Mine was home made & doesn't use a hub motor, so it neatly avoids all the above issues (at the expense of a rather noisy motor meant for a model plane)
I've said before, I like the ebikes; they enable the old or infirm enjoy cycling with more able friends, and regardless of anything they are able to put a big goofy grin on your face. Or get you to work in your work clothes and not all sweaty...
by bobc
16 May 2017, 9:03pm
Forum: Bikes & Bits – Technical section
Topic: Tyre width on a road bike
Replies: 22
Views: 8486

Re: Tyre width on a road bike

My bike of the last 6 years was on 28mm tyres, which are about as big as will go through long drop dual pivot rim brakes. The bike I use now has hub brakes (drum and disc) so I went for as big tyres as I could get through the frame, 35mm.
It is SO nice to ride - rolls great & I no longer even notice road imperfections that would have me swerving previously (so it's more relaxing to ride). Plus there's a big reservoir of air in there, the tyres seem to stay pumped up for months. Others have noted wider tyres' remarkable puncture resistance elsewhere on other threads. I expect they'll last more miles too :)
OP - put max pressure in your 30mm tyres & enjoy the ride!!!
by bobc
9 May 2017, 11:59am
Forum: Non-standard, Human Powered Vehicles
Topic: KMX X Class 16" Replacement Front Wheel/s
Replies: 10
Views: 7595

Re: KMX X Class 16" Replacement Front Wheel/s

I have a couple of rims/tyres/tubes for this, maybe some spokes but not the hubs - any use?
by bobc
15 Apr 2017, 11:10am
Forum: Bikes & Bits – Technical section
Topic: Bullbars.....(Show us yours?)
Replies: 82
Views: 24088

Re: Bullbars.....(Show us yours?)

Lots to like there colin, & always nice to see someone going beyond chequebook engineering. Particularly liking the use of housebricks as jigs for brazing :)
My brother also uses bullbars on his singlespeed. He somehow got his brake levers backwards on the bar ends - I'll give it a closer look next time I'm round there.
by bobc
2 Apr 2017, 11:49pm
Forum: Bikes & Bits – Technical section
Topic: Pedelec modification to enable hill start
Replies: 12
Views: 1038

Re: Pedelec modification to enable hill start

I've not used a modern commercial ebike solution, so anything I say is not gospel, just observations based on the limited constructions and experiments I've made over the years...
Setting off uphill is not easy. The cheapest motor controls, the radio controlled plane ESCs are all "sensorless" meaning they have no feedback of the motor's mechanical position. This actually works fine on a bike if you give it a turn of the pedals before applying the electricity, If you want reliable high torque from stationary it's usual for the system to utilise hall effect position sensors built into the motor. FWIW all systems revert to sensorless operation when they get up to a certain speed - it gives better and more reliable results than the position sensors. note this paragraph is just about making the motor turn.
Controls: Pedelecs need a pedal sensor. Again 2 sorts - position sensor or torque sensor. The position sensors are cheap and reliable (no sensitive analogue amplification required) but there has to be a change of position for them to be able to detect it - i.e. a (say) 1/4 turn of the pedals. Torque sensors must be based on some sort of strain gauge somewhere (chain stay?) and will be expensive and tricky to engineer right - but will work from the get-go.
So to get assist from first pedal pressure application on an uphill, I'd say you need all the expensive options - maybe that's what the bosch system mentioned above gives.
If I'm way behind the state of the art I apologise, I've never bought any sort of ebike, never mind a "smart" one, just played with radio control plane parts & arduino (nano) controllers on a couple of 'toy' bikes at home
by bobc
27 Mar 2017, 10:48pm
Forum: Bikes & Bits – Technical section
Topic: Brakes: Rim vs Disc vs Drum - how heavy?
Replies: 96
Views: 5030

Re: Brakes: Rim vs Disc vs Drum - how heavy?

Gattonero wrote:That's why PM mounts are widely used. If (if) there is any rubbing, undo the bolts, squeeze the lever & tighten the bolts. Job done.


Ah - I wish I lived in that world.....
We used bike cable discs on the greenpower race cars for many many years. It was never ever ever that simple. The last 2 cars have been on SA drums. they go faster and stop more reliably.
FWIW our team are world champions at the moment (the greenpower folk say "imternational champions" but I think world champions has a nicer ring to it :)
by bobc
26 Mar 2017, 7:26pm
Forum: Bikes & Bits – Technical section
Topic: My new bike has a rohloff speedhub & belt drive
Replies: 27
Views: 1988

Re: My new bike has a rohloff speedhub & belt drive

Yeah there will be a disc setup soon enough. I'm old enough and daft enough to remember my childhood experience using feet as emergency back up brakes. :) Not recent experience.....
But what does the letter of the law say? - is it illegal to use a bike with only a single brake, or just illegal to sell one? Does it depend on the age of the bike (e.g. penny farthings - did they all have a back brake?) IMO the only point of a back brake is so you still have something (however pants) if your front brake breaks.
OK looked it up - construction & use regs 1983 - I need a brake on the back on the road. If I have a prang & don't have one I'm not insured. Fair enough!
by bobc
26 Mar 2017, 2:27pm
Forum: Bikes & Bits – Technical section
Topic: My new bike has a rohloff speedhub & belt drive
Replies: 27
Views: 1988

Re: My new bike has a rohloff speedhub & belt drive

Frame is 18.23 on the sticker, I measure a 23" top tube
No the chainring isn't round, I couldn't resist putting a slight "osymmetry" on there. It reduces the belt tension in a couple of spots, but in theory that shouldn't be when there is most torque going through, should be top and bottom of the stroke,
by bobc
26 Mar 2017, 12:55am
Forum: Bikes & Bits – Technical section
Topic: My new bike has a rohloff speedhub & belt drive
Replies: 27
Views: 1988

Re: My new bike has a rohloff speedhub & belt drive

I actually bought it a few years ago for £20. It's (clearly) quite a big frame I'll get or measure the size :)
by bobc
25 Mar 2017, 2:58pm
Forum: Bikes & Bits – Technical section
Topic: My new bike has a rohloff speedhub & belt drive
Replies: 27
Views: 1988

Re: My new bike has a rohloff speedhub & belt drive

I promised pictures - here are all the home made bits. Gear changer (& cables)and back brake will be sorted out in the fullness of time...
DSC01698.JPG

DSC01703.JPG

DSC01702.JPG

DSC01701.JPG

DSC01699.JPG
by bobc
23 Mar 2017, 10:30am
Forum: Bikes & Bits – Technical section
Topic: Brakes: Rim vs Disc vs Drum - how heavy?
Replies: 96
Views: 5030

Re: Brakes: Rim vs Disc vs Drum - how heavy?

Thanks Brucey - very interesting!
Do you know offhand what the weight penalty of going up to 90mm drums is? (I suspect it's quite significant). Note also with drum brakes, all the spokes can be a bit shorter.....
discs v drums I see 2 big drum plus points - 1) no drag when brake off (very difficult to adjust real world discs to achieve) and 2) very simple to adjust when (rare) adjustment required (disc calipers typically have 4 possible adjustments; cable stop, clearance, 2 positions). They are also better protected than discs, little affected by conditions and modulate just fine - yes I'm a fan.....