dynamo tyre wear

[andrew_s]

also what do the bits in red and green mean?

The red is a diode, green is "no connection"
It is not a good circuit for the careless or inattentive.
The dynohub will be trying to deliver about 0.5 amp, and if the USB port isn't taking that much and the batteries are fully charged, the voltage will rise until something gives - either blowing whatever is plugged into the USB, or more likely cooking the batteries. You would want to run off the batteries until you got a low battery warning, then close the switch and charge & power for a while - up to 5 hours perhaps, but not so long that the battery reached full..

 

[young Ed]

SIC - is a product I linked to in an earlier post
istr - standard abbeviation for "I seem to recall"
red & green bits - if you don't know what that (standard circuit diagram symbology) is all about just don't go there, put your soldering iron away and buy a comercial product instead.... several have already been suggested to you.

Sorry it having been a long tiring day and having mind go blank combined meant i managed to forget all but how to write my name etc but when I looked at it today I immediately recognized them and kicked my self!
So might still try.
Just to make sure i don't f anything up the diodes are to convert the ac to dc right?
Cheers Ed

 

[Davidc]

Yes, the AC dynamo** output needs to be turned into DC.

I totally agree with andrew_s. I'd suggest if you go down this route that that circuit would be best used with two sets of NiMH cells, and the set not in the bike charger used with your Garmin. That way if you cook the charging set your Garmin will survive!

**Although the word dynamo is most commonly used for DC generators, bike dynamos are a type of generator called a magneto. It uses permanent magnets on the bit that goes round to produce current in fixed coils. The system is contactless and inherently produces AC. ( I have however seen one advertised which contains a rectifier and has DC output).

If you're interested - PM me - I have a document produced as briefing notes for an A level Physics group who were using them in a project, which I'll attempt to attach to a reply!

 

[Davidc]

Rear hub is complicated enough without a dyno.
Don't try to re-invent the ....er .... wheel (sorry)
Go with a front wheel dynamo hub - it will be the same 100mm spacing as your current wheel (unless you have something very weird)

This is stupidly good value..... basically a rim, spokes and wheel build thrown in for less than a £ over and above the price of the dynamo.
The rim is not super high end, but it is very adequate and ideal for the 700x38c you want to run - personally I'd go narrower but that's just me.

Don't forget you need DC 5V for the Garmin (USB standard) and 99% of hub dynamos will give AC at constant current(-ish) and voltage varying according to speed.

ISTR you are into soldering in which case you "could" do this (missing out the Philips Saferide if you don't need lighting)

The impedance of the rechargeable cells will ( I gather) give you the over-voltage protection on the USB - although it might be safer to run it via cache battery (choose a model that can both charge and be charged at the same time - not all can).
Alternatively buy that Pedalpower SIC I recommended earlier.

The wheel in that link is stunningly good value. That's what I have on my tourer and the components cost me over £80 5 years ago!!!!!

Not to mention a day building it.

 

[young Ed]

This is stupidly good value..... basically a rim, spokes and wheel build thrown in for less than a £ over and above the price of the dynamo.
The rim is not super high end, but it is very adequate and ideal for the 700x38c you want to run - personally I'd go narrower but that's just me.

may well get that set if i can save up for it after my garmin
is it preassembled?
two sets of NiMH cells, and the set not in the bike charger used with your Garmin. That way if you cook the charging set your Garmin will survive!

If you're interested - PM me - I have a document produced as briefing notes for an A level Physics group who were using them in a project, which I'll attempt to attach to a reply!

this confuses me???
yes please will send a pm
Cheers Ed

 

[young Ed]

could i run a 28 inch wheel in place of a 29er wheel?
http://www.ebay.co.uk/itm/28-inch-f...sure_cycling_bikeparts_SR&hash=item35ced01d1a
Cheers Ed

 

[Rickshaw Phil]

could i run a 28 inch wheel in place of a 29er wheel?
http://www.ebay.co.uk/itm/28-inch-f...sure_cycling_bikeparts_SR&hash=item35ced01d1a
Cheers Ed

Yes, because that is a 622mm diameter wheel which is the same diameter as a 29er wheel. It's best to look for the ETRTO sizing as inch sizes are incredibly confusing. For example there are about six different sizes that are called 20 inch - none of which are compatible with each other and the 700C (622mm) sizes can be referred to as 27, 28 or 29 inch. A real minefield.

 

[mcshroom]

If you fancy really confusing yourself Ed: -
http://sheldonbrown.com/tire-sizing.html

Simply put, 29er/700c wheels have a 622mm diameter.

 

[Rickshaw Phil]

The Schwalbe link I put in your other thread has a good list of all the various sizes available too.

 

[young Ed]

Yes, because that is a 622mm diameter wheel which is the same diameter as a 29er wheel. It's best to look for the ETRTO sizing as inch sizes are incredibly confusing. For example there are about six different sizes that are called 20 inch - none of which are compatible with each other and the 700C (622mm) sizes can be referred to as 27, 28 or 29 inch. A real minefield.

how do you know it is 622mm diameter?
why make it so confusing for me?
i just liked the look of that wheel as it is cheap!
Cheers Ed

 

[Rickshaw Phil]

how do you know it is 622mm diameter?
why make it so confusing for me?
i just liked the look of that wheel as it is cheap!
Cheers Ed

It says in the description that it's 700C and further down where it goes into more detail says it's ETRTO size 622-19, which is 622mm x 19mm.

For what it's worth, it looks like a decent spec wheel for the price to me.

 

[Andrew Br]

why make it so confusing for me?

Cheers Ed

It's not just confusing for you

.