AM dual motor = bafang middrive + rear hub motor

[John Bozi]

avoide radial lace if you can, it will be ok for a few months but the life span is so short becuaes spoke are being pulled very hard because there is no tngental angle to transfer torque.

19" bmx/trials rim the pedals will hit the ground with out leaning!!

honestly go for 17" mc or something. equal 22+ out side diameter (how bicycles are mesured)

I am only using 2.8k at full charge, do you have any case proof of failure due to only riding? (links to the basis) I am not into jumps (apart from the front lifting up)

the pedals if you look in the last few posts Ive been collecting info about pedal shortening.

its all a trade off. drill a hole you get shit inside.

put 18 cells on your bike its heavy

put electricity you will end up burning yourself eventually

increase your mountain climbing ability - a frock load of custom jobs to do

Not everyone lives in a flat area or is ready to stuff around with mid drives. (yet)

 

[pendragon8000]

ah yes a saw that... well if you want to shorten pedal cranks then i guess you could go stupid small 19" bicycle trials or 16"mc . i think 17 or 18 mc would be ideal. are you doing fire trails or street these days? or both?

 

[John Bozi]

ah yes a saw that... well if you want to shorten pedal cranks then i guess you could go stupid small 19" bicycle trials or 16"mc . i think 17 or 18 mc would be ideal. are you doing fire trails or street these days? or both?

Street is for reasons - shops - visit people (not commute to work = nowhere to park safely for free

Off Road is for fun -

I'd do more off road the more hills I can conquer quicker. Waiting for heat to drop takes time, half time I just push the bike until it has cooled- unless I've got brews n cigs in the back pack = have a little picnic boo boo.

I intend to do the

holes near perimeter on one side
holes near centre the other side

venting - I won't go too large with the holes as I think going to shorter spokes is already going to put more stress on the motor and axle strength.

I know one day I will cave in and buy the best mid drive out there. At that point I'll convert this bike back to on road.

Edit: I am starting to get more worried. Pedal shortening doesn't look like it's going to work with the shaped cranks I have.

Went to find my bike on the site I bought it but looks like they dont sell it anymore but they do in USA for $1200 now... ($400) cheaper than I paid.

I am wondering weather bmx cranks can be much smaller and if there is a way to fit them

one dood in the UK http://www.highpath.net/highpath/cycles/shorten.html#suitable

NOT POSSIBLE ...

hollow cranks (eg. Shimano Hollowtech)
steel cranks
carbon cranks
very narrow cranks (narrower than 25mm at the new pedal position)
deeply fluted cranks (leaving less than 10mm material thickness)
AND ...
cranks cannot be shortened by less than 20mm

... SO ASK YOUR BIKE SHOP FOR ...

SOLID, UNFLUTED, ALUMINIUM CRANKS.
(I'll contact you if you send me something unsuitable.)

Edit:

Spun out the guy I bought the rim off refunded me $27 on shipping! so the rim only cost me $50 something now...

Also creepy crawlers are about $35 plus shipping. Local bike shop quoted me $30.

so somethings are looking brighter. I'll go visit LBS.

 

[John Bozi]

I started my ride today on 74.8/7v since overnight I lost about point .2

I finished my ride with:

69v 20kms 5ah
av speed 23kmph, sure when I'm up the mountain I do lots of pedalling on anything flat as there isn't much of it.
finished off 3.85 average over every cell, checked each battery separately. Not much either side of that.

but best of all I have never ended up like this:

12% regen

Was paranoid as I didn't use balance leads/monitors. But rode up the mountain for an amazing 50 minute ride.

 

[pendragon8000]

12% is a good return . do you have it set to hard regen level or "normal"?

 

[John Bozi]

12% is a good return . do you have it set to hard regen level or "normal"?

Pretty sure its on hard, but it never feels hard to me.

It really saves my brakes.

 

[John Bozi]

This site looks like my only real option for the pedal chainring strike problem. No idea if it will work with my BB. Looks like $$$$ spent
http://bikesmithdesign.com/Short_Cranks/s600.html

Race Face Narrow-Wide Chainrings
These rings keep the chain from coming off, without retention systems.
S600 with 30t Chainring (150mm Shown)

120mm S600 - $165 for 30t

In order to fit a 30t ring on a 104mm BCD, the female part of the chainring bolt is machined as part of the chainring, adding to material and machining cost.

 

[John Bozi]

[youtube]xG4oIebZFQI[/youtube]

this little tyre is gona cost me heaps, got 20" by 3" tube to boot from LBS for $38

I may have to recalculate this after measuring. For some reason I thought the cranks were in exactly between the wheels.

Edit: more calculations: The wheel base is actually 1124.6mm - so I was calculating an average height between 19" and 26" at 562.3mm in the middle.
but rear centre is 430 mm so I actually need to chop off more than 2". My math is terrible. Help!

Actually if my cranks are 175mm as most are then 55mm is probably just right with 120mm cranks.
Going from the 42t to 28t only will save about 35mm also on the chainring, which will be essential going over humps and compressing the suspension. I haven't checked to see if lowering suspension 100% compression will hit the unmovable last 2cm.

Have had a few backward forward emails with Mark the bikesmith guy.

I have learnt:

There are no shortenable cranks that will fit my BB, which has external bearings.

The good news is that I have a threaded BB shell. Whether it's 68, 73 my local bike shop will be able to help.

A square taper BB cartridge will fit. I will need one with a 113mm spindle length and for either a 68mm or 73mm BB shell.

Looking on the net trying to get my head around all this vocab I am happy to see the BB shouldn't cost more than $30 max. This one for example http://www.bicyclestore.com.au/shimano-bb-un55-square-taper-bottom-bracket.html

If radial is good enough for "zappy" it will be strong enough for me.

David Karas on fb: another cro radial bmx

 

[John Bozi]

After much searching various options (there are many cheaper but not so sure they'll work)

I have decided to buy a black 30t Race Face Narrow-Wide Chainring with s600 cranks shortened to 120mm for $217 Aud including shipping.

Sounds like a lot, but I justify this as not being a crazy price when you look at expensive drive trains mountain bikers pay.

Mark Stonich, the guy running bikesmithdesign.com, is a great guy and very patient with many of my newb questions.

Happy to spend the money and save myself the headache of doing it myself.

 

[John Bozi]

Does it look right? I am trusting Alex rim specs on there website for the new ERD

Last times I stuffed my rim and then a spoke I brought up this information:

ERD 533
spoke hole 3mm
Fl width (between spokes) 50mm
flange 40mm
spoke hole to spoke hole diametre 232mm

12 gauge = 4mm spoke nipple wrench

 

[pendragon8000]

Little bit of help:

From this page
http://www.electricbike.com/cromotor-monster-hubmotor-for-electric-bikes/

 

[John Bozi]

@pend Which part of the linked article is useful? 20″ wheel = 36mph / 57kph @ 37A in a cro? (just a random guess)

Finally, got replies from gloworm saying that erd will change if you drill out the eyelets.

now mmmmmmmmmmmmmm mmmm

 

[pendragon8000]

By like 1mm don't worry about it.

The use full bit us the custom dropout adaptor that has the raised frame.

 

[John Bozi]

custom dropout adaptor that has the raised frame.

wholly, how did I miss it - I just glanced and looked a torque arm solution....

I was looking at the paired spoke whole idea but to me drilling into the hub looks very difficult and probably not even possible when there are already so many holes that might get in the way of the new method. If I were to drill Abraham recommended the 14/13 spokes (no change to eyelets)

I cant do it so I am going to have to stick to 12 gauge (so that the head is snug) and just deal with repairs (lots of extra spokes). If I get sick of it enough I'll have to start again with the rim (won't regret the chopped peddles as I would drop the front too to match)

How much power are you going to run through the BMX?

 

[pendragon8000]

75v 80a . should top out st 60kph so for general use it won't be too thirsty.
It should pull very hard off the line though. And very low center if gravity. Might be making triangle battery box this weekend. Aluminium painted satin black.
I'm going to get a disc hun for the front and have it laced in an Alex DX 32 20" and weld a disc mount on an old bmx fork.

 

[John Bozi]

As I am considering going to less than 12 gauge I am looking for solutions to make less stress on the hub eye.
MadRhino uses

Conic flange washers made out of alu pop rivets. They make a tight fit and last incredibly long.

http://endless-sphere.com/forums/viewtopic.php?f=3&t=46886&p=900944#p900783

 

[John Bozi]

measured inside the rim:

either 365-366 for inside the rim to inside the rim
or about 364 from inside top of the eyelet to the eyelet opposite

trying to measure top to bottom of eyelet by sticking the head of pen in the eyelet with crude pen marks the eyelet appears to be 4mm thick and measuring how much it sticks out the inside of the rim is about 1mm which is probably how much it sticks out on the inside. guessing the rim metal is 2mm thick.

that would be 366 + 2+2 = 370
with eyelet stuff and poor eyes and tape measurement skills = 371 (from alex) which is my original 72.4mm long spokes.

40 x 13/14 black sapim $1.9 = $76? (including nipples/postage) = $84.25 AUD

From Abraham @ Gloworm

The calculated spoke length relies on on accurate measurements which I can't do for you but an ERD between 370mm and 374mm gives a spoke length difference of 2mm. 72.5mm is close to the middle of those 2 values so hopefully it's close enough!

I can also roll longer than normal threads (12mm long vs the standard 9mm long) which will give you more wiggle room in case the spokes end up on the long side.

longer thread thanks.

I'm guessing they look like Justin's @ ebikes.ca

From a post at Tarty bikes

Hi John Bozi,

Thanks again for your question about the Alex DX32 19". The reply to your question can be found below:

--------------------

Question:

On the alex site its listed as 371 erd, are you sure about your 374?



Answer:

Hi John - thanks for your question, and thanks for pointing this out. To double check, I went and measured one in the warehouse, and they came in at 371mm. The 374mm came from the older version of the rim that featured eyelettes, slightly increasing the ERD. This did not get updated when the un-eyeletted version arrived. I will update the site so that it shows the correct ERD of 371mm now. Thanks again! Flipp.

That's a 1.4mm of different length spoke.

 

[pendragon8000]

In my experience the drive spokes stretch and end up being a bit longer anyway . if you make them just long enough going toward the shorter measurement you come up with , by the time you wear them in and tighten it up they will fill the nipple and not protrude into the tube area. If they are a tiny bit long at the start they may stretch and start rubbing the tube eventually causing a puncture.

...
Did you see my new pimp axle nuts?
I think you should give them a go. Super cheap auto near you? 1/2 inch lug nuts they feel so solid going on using up so much of the threaded axle , and bigger socket to grab it with and look nicer, also protects the axle end $15

 

[John Bozi]

Im not changing my final choice on spokes. They are in with Abraham now and the cranks/chainring should be here in a couple of weeks. That completes all the purchases for the wheel change. (apart from some rim tape and future studies of how low can you go with the front wheel)

If comparing like to like wheel builds (same rims, hubs etc), smaller wheels will always inherently be stronger than larger wheels. This is due to wider gaps between spoke eyelets as just one reason.

Getting into the old boring 26 vs 29 debate for the purposes of thinking of my own 20" vs 26 rear debate I will continue to have.
http://bansheebikes.blogspot.com.au/2013/10/wheel-size-facts-part-1-dimensions.html

Small radial vs large cross is my current search and study...

I am only hoping that I am right = that the wheel strength of a 26" cross pattern is equal to a 19" radial.

I am only 170cm tall, and have always found mountain bikes vs bmx way to tall for my comfort level. I am looking forward to the drop of about 6cm at the saddle every time I get on and stop. I would like to be able to have my foot flat on the ground. I am guessing I'll feel more adventurous cornering too if I work out my final future issue of derailleur strike.

 

[John Bozi]

Current method of dealing with heating issues is stop when you hit 105 have a brew and a cig. Lovely ride today, bit cooler, so making it a bit further before overheating. Backpack is mountain bike style although a 6 pack of coopers -my favorite Aussie beer.

Takes 5 minutes to have a smoke beer and cool down by 30 degrees.

I don't know where I'd be without my velcro. The 60cm long ones are best off ebay - $2 for 10 or something like that. I've ordered more as the the 30cm coloured ones are ugly and too short. Although they do connect to each other.

I am not too interested in aluminium boxes anymore, I like my tape, neoprene, pvc velcro strapped. After I have a smaller wheel there will be a large area between the seat tube and rear wheel I didn't have before... mmm

 

[John Bozi]

[youtube]WYadmWdYPRg[/youtube]

 

[trevc2]

I am wondering weather bmx cranks can be much smaller and if there is a way to fit them

BMX cranks in small sizes can get pretty expensive too, and you'd need to order from overseas.

Unicycle cranks come in any size you want, and they start as cheap as $15. Standard mounts, ISIS, etc.
http://www.municycle.com.au/View.php?action=Page&Name=Cranks

Not sure how much that helps, but wanted to paste the link before it was too late

 

[John Bozi]

I am wondering weather bmx cranks can be much smaller and if there is a way to fit them

BMX cranks in small sizes can get pretty expensive too, and you'd need to order from overseas.

Unicycle cranks come in any size you want, and they start as cheap as $15. Standard mounts, ISIS, etc.
http://www.municycle.com.au/View.php?action=Page&Name=Cranks

Not sure how much that helps, but wanted to paste the link before it was too late

it is too late but I looked into both those options already thanks. unicycle doesnt have a way to bolt the chainring, bmx were all out of stock everywhere I looked.

I've paid for everything and just waiting for delivery - in 2 weeks I'll start the build.

[youtube]hbKvLc3fvpE[/youtube]

I dont need muddy maries I need something for dry gravel, thats what I slide out on the most.

 

[drew12345]

Cool video! I like all the 3rd person view shots.

 

[TotalConfusion]

Great site that Unicycle shop for 24 inch Hookwoorms http://www.municycle.com.au/View.php?action=ProductDetail&Code=UPTYRHW

Your bikes coming along nicely Jon