Return to the bent!

[Benjahmin]

jeez! Been searching for about 3 hours. Cannot find a 26" 36 H black double wall rim of 19-21mm width with no eyelets.
Are the eyelets a deal breaker?
I have, so far, only looked at rims under £40

 

[Nealh]

Rigida Zac 2000 se Bicycle Rim - 26" - MTB - TOUR - black - 32 or 36 hole | eBay

>Rigida Zac 2000 se Bicycle Rim - 26". These are really excellent quality rims that are good for MTB, Touring and even Cargo Bike use. 530g per rim. 32 or 36 hole drillings. Single eyeleted. Colour - black.

www.ebay.co.uk

Pardon our interruption...

 

[Nealh]

Seems prices have risen on 26" stuff nowadays.

 

[saneagle]

jeez! Been searching for about 3 hours. Cannot find a 26" 36 H black double wall rim of 19-21mm width with no eyelets.
Are the eyelets a deal breaker?
I have, so far, only looked at rims under £40

Eyelets don't matter so much if you use 14g spokes and nipples, which I'd recommend anyway.

Can't you save some money by using your present rim?

 

[Benjahmin]

Thanks Neal, I searched bankrupt bike parts but missed that one. Just ordered it.
Thought of using the existing rim but have a notion to sell the wheel/motor.

 

[Benjahmin]

While I'm waiting for the rim (thanks for the help chaps) I'm looking at the gearing.
Currently the rear cluster is a 14-28 freewheel. I find the ratios a bit close, it's difficult to feel when it has changed so often end up going two. On a bent, it seems you have to spin more on hill climbing. Front to back ratios seem OK ish on this point but top end is a bit lacking, so looking to increase the ratio here.
8 speed cassettes seem to have a greater variety available. Not sure whether to go 11-30 or 11-32, think 11-34 may be too far. Derailleur is a long cage so should handle the extra.
Can get a Shimano 11-32 in black for around £16, but will the difference between current 28t and new 32t be too much? If so I'll go 11-30 in silver.
Gearing's such a personal thing so difficult to say, but what's the feel?

 

[AntonyC]

8 speed? That depends on how many gears your shifters are indexed for (or whether they do friction mode) - your cassette is 7 speed so tell us more.
Your derailleur spec will say something like Max. teeth large sprocket 36, Total Capacity 45. Subtract the range of your chainrings (52-28=24?) and that leaves 21 for the cassette, so in that case whatever you can find between 11-32 and 15-36 would be OK, in however many speeds your shifter can handle.
Obviously check the derailleur for wear and damage first.

 

[Benjahmin]

Thanks - not sure I understand the maths, however, I have bar end shifters and the rear one's indexed for 8 (deraileur is currently restricted to 7).
Main aim is to increase the 'space' between ratios so I can feel the difference so it's probably going to be the11-32.

 

[Benjahmin]

Plan is to use my Ezee rear rack battery which fits on a top hat din rail. So, easy enough. However the Velotechnic rack is only 130mm wide whilst the battery is 150mm. Could just mount it on top but this would stop me being able to hook panniers over the top bar. Was thinking of buying a double decker rack and butchering it (with finesse!) to fit on top of the existing rack. I've found one on fleabay for £60 that would do the job but, the skinflint part of me finds paying that much to be butchered offensive. Also, because of the length, it would overhang the existing rack, and we all know how awkward that can look.
So trying to think my way round/through this one.
Considered batteries in panniers. Not great and robs me of shopping/picnic carrying space.
Any thoughts?

 

[Benjahmin]

The rim has arrived. I've watched the Grin wheel building and hub measuring video's and will be measuring stuff tommorrow. I read the Sheldon Brown stuff too, but I couldn't retain it. I function better with visuals.

The motor had this sticker on it:

I've removed it and this was underneath:

So an AKM motor rebranded as Topbikekit.

 

[guerney]

Could just mount it on top but this would stop me being able to hook panniers over the top

I did eventually find pannier bags which go over my rackmounted downtube battery. Cheapos, but they did the job until I saw sense and got bike trailers instead. I can try and find a link for you if you're interested, they cost me less than a tenner (at the time).

 

[Benjahmin]

Just spotted that, on the TBK spec, the motors' gear ratio is 10.5, whereas on the label it says 8.1.
I'm assuminmg this means that the rotor will spin slower for a given rpm. As this motor is specced at 48v/328rpm but I'll be using it at 36v to get 250, will this be a problem given the slower rotor?
Or am I overthinking this and should just go and dig the spuds up whilst it's not raining?

 

[Woosh]

There isn't much you can change, so I would just continue with plan A.

 

[saneagle]

Just spotted that, on the TBK spec, the motors' gear ratio is 10.5, whereas on the label it says 8.1.
I'm assuminmg this means that the rotor will spin slower for a given rpm. As this motor is specced at 48v/328rpm but I'll be using it at 36v to get 250, will this be a problem given the slower rotor?
Or am I overthinking this and should just go and dig the spuds up whilst it's not raining?

The motor RPM is the outside speed, so it'll be 260 rpm at 36v.

 

[guerney]

Could just mount it on top but this would stop me being able to hook panniers over the top bar.

I did eventually find pannier bags which go over my rackmounted downtube battery. Cheapos, but they did the job until I saw sense and got bike trailers instead. I can try and find a link for you if you're interested, they cost me less than a tenner (at the time).

Found it:

Pardon our interruption...

Not waterproof without this:

Pardon our interruption...

They still do the job in a pinch, despite having been used a lot.

 

[Benjahmin]

Thanks Guerny, might consider those 'cos they obviously help you get up hills fast

 

[guerney]

Thanks Guerny, might consider those 'cos they obviously help you get up hills fast

Helpful and amusing. It's 3A extra that's increased my uphill speed, and the subject of another thread - I hope your bent doesn't get chased by people on foot uphill.

Those cheap and nasty pannier bags held up really well, though I totally understand if they're not the sort of low quality product you'd consider buying - the reason why I linked them, is because you asked a question, and because there may be better crafted products of similar dimensions and design to fit over a rear rack mounted downtube battery. Too much weight on the back didn't work out well ascending very steep hills, of course.

I'll ignore your posts and won't see them. I suggest you do the same. Despite apparently knowing a lot about bikes and batteries, you don't appear to try helping people out on many other threads, so I don't think I'll be missing much. The "Ignore" feature of this website is a good one.

Thank goodness for helpful members, who also know a thing or three.

 

[Benjahmin]

Ooops! Shows how attempted humour can go wrong without the aid of facial and tonal expression.

Got everything in place now to start measuring for spokes and the learning can continue.

 

[Benjahmin]

Using Grin's methodology and calculator, I've arrived at spoke lengths of 207 and 206mm. That's fine but, their graphic display reckons I'll get 72% tension one side and 28% the other to get the offset. The advice is to be as close to 50/50 as possible but nothing I alter (within measurements) makes any difference.
It's my first attempted wheel build and 72/28 seems a bit extreme, or am I suffering from information overload?

 

[saneagle]

The difference in tension between the two sides goes up exponentially with the amount of offset. At 20mm offset, the spokes on one side would need zero tension. You can't really make a judgement until the wheel is in the frame. You can mitigate the offset by adding spacers to the axle on the brake side, but then you have to open the frame a bit more. That works very well for rim brakes, but you have to be a bit more creative with spacers for disc brakes to get the disc to line up with the caliper.