hkckoo

Hi all bike enthusiasts. Currently riding in the city in a mixed flat/hilly terrain (well there is one hill that I am struggling with)
I am mostly using 4th and sometimes 3rd gear. 2nd when climbing slight hills and the 1st gear only on the one steep hill that I am struggling with. but like 80-90% of time I am in 4th gear. So from the new 7speed hub I would appreciate a slightly harder gear than I currently have, sometimes I get bored when riding on flat terrain.

This is what I came up with, I am open to suggestions as to a ring/cog combination that would do better.
https://ritzelrechner.de/?GR=SAX8&KB...Z2=14&UF2=1380

Yes, I do use 18 inch wheel, my bike frame is highly specific/non-standard. I use this to move around https://halfbikes.com/

Though I must say I am afraid of such a setup, as I am rarely using 2nd gear on my current hub, seems like I would lose first 4 gears on my new kindernay hub.
Any recommendions?
I am not sure I will be able to fit a 12t 9-spline cog on the hub, but I think it is possible, then the ratio would look like this
https://ritzelrechner.de/?GR=SAX8&KB...Z2=12&UF2=1380
and seems like a better suited option, but this is my first time building up my own gear setup.
thanks in advance for any advice.

kommisar

According to this page:

https://www.sheldonbrown.com/internal-gears.html

For a 5-8 speed IGH your second highest gear should be ~5.6 development. Since you want a bigger gear, I would adjust this formula so that your 3rd highest gear was ~5.6 meters development. I would bias my sprocket choices toward the largest cog and largest chainring practical to achieve this, definitely larger than a 12t. The reason being that larger cogs wear longer than smaller ones.

hkckoo

Ok, thanks, this is useful info, so from these findings, going for 14T cog and 46T chainring seems like a better option
https://ritzelrechner.de/?GR=KND7&KB...Z2=14&UF2=1380
I am just not sure how much I will utilize gears 1-3 with development 2.2-3.5meters when I am rarely using 5-6m development on my current sturmey archer hub (first two gears)

kommisar

Looks good. Ride it. It is relatively cheap to adjust your gear range by changing the rear sprocket if you don't like the current setup.

Dan Burkhart 

You didn't mention what brand of 4 speed you currently have but both Sturmey Archer and Shimano 4 speed hubs are direct in first with no underdrive gears.
Switching to a 7 speed Shimano hub will give you underdrive gears and a slower ratio at the top end than you currently have so you will want either a smaller sprocket or a larger chain ring for sure.

ofajen

The Halfbike 3 uses an SA hub, but I wonder if it is a specific OEM product made for their machine? Otherwise the gearing should be high enough. With the normal 4 speed hub, if the cogs are 42/14, it would range from 54 to 113 gear inches, I think. That would be 4.3 to 9.0 meters. Do I have the chainring and rear cog correct?

Otto

GamblerGORD53

WTF. TROLL-advertisement..
116 GI = way over 30 mph. On that clown POS standup scooter that will only do flat MUPs ???

hkckoo

yes, half bike 3 uses standard sturmey archer RX-4, the one with drum brake. no OEM product. the chainring and rear cog are correct.

hkckoo

yes, that is true, current hub has no underdrive gears, this new hub has 3 underdrive gears. i guess i will start with 46T/14T and go from there, thank you all.

hkckoo

<br />yes, because everyone wants to be riding their bike standing up, go buy three for the price of two now.