38t chainring on Amflow

SimonG said:
Para quem mais estiver lendo isso... o autor da postagem acima é um troll arrogante que acha que sabe tudo e tem uma opinião formada. Apesar de ter solicitado repetidamente os cálculos de falha do material, não recebi nada. A empresa que contratei fez os cálculos de engenharia e presta serviços para a indústria aeroespacial. É confiável.
Click to expand...
nuuuuuu 👏👏👏👏👏👏👏
 
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Spider_6.webp


Had a little project the last few weeks to get some more tooth on my front chainring since the max allowed 38T weren't enough for my taste. Even if in low power eco settings the chain almost always lingers around the smallest 3 cogs (its rather flatlandish in my vicinity) and too often on the smallest one. So 40T or if possible 42T would be nice which apparently only would work with a custom spider. Although i considered to put some washers between the default spider and the motor interface get some room for larger chainrings i decided to make my own since the avinox thing looks rather bland.

Spider_SCAN.webp


Working out the CAD fortunately wasn't a problem since i do this stuff all the day. However the devil is in the details - as it turned out after scrutinising every iteration of my attempted spider . For the first drawing the chainring bolts most likely would have hit the motor block, the second one was probably a bit to thin partially and had the potential to crumble under full load. The third one finally passed the the checklist. The final layout shifts the chainline 2.5 mm to the right side. On the color side i was a bit undecided between some decent silver or some less lowkey red. I went for red.

Spider_CAD.webp


Next hurdle: get someone to make it. I first searched the web for some companies doing small batch sizes but no one of them even bothered to answer my mails. Next one was checking some sort of "graigslist.com" only for germany (kleinanzeigen.de). Turned out there were some offering carving shapes out of metal but none of them in an acceptable price range for T6 or T7 aluminium with anodized finish. So I ended on aliexpress where i found a company with a nice and capable lady which convinced me to use some T6 alloy. Out of curiosity I also asked for T7 or titanium which she was very unwilling to offer primarily because it would have much more impact in degrading their tools. Titanium would had cost me 5 times the price compared to aluminium T6-6061. It took then roughly 2 weeks on their side until shipping. Cost: 185€ for production including shipping plus 25€ import duty.

Spider_2.webp


Spider_3.webp


Conclusion: works as expected, the 40T fits with around 2 mm distance to the lower chainstay. With default sag its around 3 mm. The chainline looks a bit more ugly now if on the largest cassette cog but all works fine still without making any additional noise. As a nice side effect i now could swap chainrings without disassembling cranks and spider first. 42T probably also would work if using a washer of around 1mm between spider and chainring.

Spider_4.webp
Spider_5.webp
 
Wow, nice work! I'm just going to buy the SRAM 38 when it comes out in July and bend it. 😋

How does 40T get along with the computer? I'd expect it to throw some errors, but maybe Avinox isn't as uptight as Bosch, whose tamper detection algorithms will immediately disable the motor if you fart too strongly.

Also, that's an amazing price (and delivery time) for a custom part with time-consuming broached splines!
 
ericm said:
I just bolted an Sram 38t to the existing carrier. It clears the frame with no issue.
Part # 11.6218.057.002
Click to expand...
Curious why OP milled out a couple millimeters then? Is it only the Eagle 38T that doesn't fit, while the T-Type does?
 
Gauss Guzzler said:
Curious why OP milled out a couple millimeters then? Is it only the Eagle 38T that doesn't fit, while the T-Type does?
Click to expand...
Thats probably contributed to his personal feelings about "safe space", from a technical point its not necessary. In 29" mode (flipchip) the clearance is about 2mm. In 27.5" its a bit less, which I rode with a 38T for more than 3000 km with not a single scratch in my chainstay. Besides as soon as you sit on your bike the clearance is ~1mm more.
 
I have the SRAM x sync 36t and would like to go 38t. Some have said the sram 38t fouls but some have said the hope works. What the difference between the two
 
petro1head said:
I have the SRAM x sync 36t and would like to go 38t. Some have said the sram 38t fouls but some have said the hope works. What the difference between the two
Click to expand...
The Sram is steel. The 38t part number I posted earlier in this thread fit my PL Carbon just fine. It's the 38t version of what came on the bike.
 
nowayfra said:
View attachment 183976

Had a little project the last few weeks to get some more tooth on my front chainring since the max allowed 38T weren't enough for my taste. Even if in low power eco settings the chain almost always lingers around the smallest 3 cogs (its rather flatlandish in my vicinity) and too often on the smallest one. So 40T or if possible 42T would be nice which apparently only would work with a custom spider. Although i considered to put some washers between the default spider and the motor interface get some room for larger chainrings i decided to make my own since the avinox thing looks rather bland.

View attachment 183977

Working out the CAD fortunately wasn't a problem since i do this stuff all the day. However the devil is in the details - as it turned out after scrutinising every iteration of my attempted spider . For the first drawing the chainring bolts most likely would have hit the motor block, the second one was probably a bit to thin partially and had the potential to crumble under full load. The third one finally passed the the checklist. The final layout shifts the chainline 2.5 mm to the right side. On the color side i was a bit undecided between some decent silver or some less lowkey red. I went for red.

View attachment 183978

Next hurdle: get someone to make it. I first searched the web for some companies doing small batch sizes but no one of them even bothered to answer my mails. Next one was checking some sort of "graigslist.com" only for germany (kleinanzeigen.de). Turned out there were some offering carving shapes out of metal but none of them in an acceptable price range for T6 or T7 aluminium with anodized finish. So I ended on aliexpress where i found a company with a nice and capable lady which convinced me to use some T6 alloy. Out of curiosity I also asked for T7 or titanium which she was very unwilling to offer primarily because it would have much more impact in degrading their tools. Titanium would had cost me 5 times the price compared to aluminium T6-6061. It took then roughly 2 weeks on their side until shipping. Cost: 185€ for production including shipping plus 25€ import duty.

View attachment 183979

View attachment 183980

Conclusion: works as expected, the 40T fits with around 2 mm distance to the lower chainstay. With default sag its around 3 mm. The chainline looks a bit more ugly now if on the largest cassette cog but all works fine still without making any additional noise. As a nice side effect i now could swap chainrings without disassembling cranks and spider first. 42T probably also would work if using a washer of around 1mm between spider and chainring.

View attachment 183981View attachment 183982
Click to expand...

Hi there,

Would you be interested in sharing your spider design ?

Thanks
 
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