CYC PHOTON

[Mongo]

What is max motor RPM in photon?
For example max RPM in stealth is 4000

I thought the CYC's Photon specification said 3800rpm unloaded for the motor core (not spindle or cadence), but my DS103 display reads approx. 3200rpm (bike run unloaded on a repair stand).

All of these motors run way past a human-pedalable cadence - including possibly the ToSeven DM-01, with its very BBSHD-like 160 unloaded cadence (per their spec). Do they all really need but mechanically can't fit a third reduction stage?

I've been working on gearing my current Photon-motored, IGH hub bike build so that it kinda has two separate workable low/high ranges - a wide enough torque pedaling range down in the seventies cadence, and another wide enough full throttle one in the 130-150, motor comfortably spinning cadence range - with 1-2 gears at opposite ends of both ranges which will mostly go unused.

Maybe it's not realistic to have the motor full-power torque-assist down at a cadence where I can keep up - could the controller accurately measure my measly leg input when cranking out higher full power levels?

 

[Wattman]

All of these motors run way past a human-pedalable cadence - including possibly the ToSeven DM-01, with its very BBSHD-like 160 unloaded cadence (per their spec). Do they all really need but mechanically can't fit a third reduction stage?

Well, depends on what chainring. Bicycle gearing of course is the third reduction including wheel/tire diameter.
As mentioned a BBSHD bike with stock controller and not field weakened controller and 30 amps will turn about 3700 RPM.
Bafang did a heck of job with the sweetspot of their gear reduction.
With a 52t chainring and 11t cog in back I can hit close to 40 mph and not quite spin out. If you think about this gearing, it is close the top gear on a racing bicycle where top sprinters can hit 40mph in a sprint at high cadence/RPM without a motor at about 1200-1500 watts human power on a very light bicycle.

As to why not? Demographically and statistically speaking, it isn't relevant other than for maybe 10% of ebike riders. A third reduction stage would add weight, complexity, have a higher reliability cost but moreover it would also cost more to the consumer who generally doesn't need it or want to pay the premium.
Most don't want to ride a bicycle with a motor faster than 40 mph whether they can keep up with their feet or not. In fact, low 30's on a bike is decent top speed or 35mph or so in my experience as I hit these speeds when racing with my friends, some without a motor btw who are national competitors.

You are knowledgeable ncmired and want to ask, all said are you happy with your new Photon? Would you consider yourself a performance rider and touch 30 mph once in a while? Have you owned other Bafang products as a basis for comparison? No doubt the torque sensor is nice.

 

[Mongo]

CYC gripe time.

I'm hoping I'm wrong, but I've yet to come across cable options/extensions for the Photon motor system - mainly for the motor to the main harness cable and the speed sensor cable. Up at the bar end, you can use the generic Bafang/Tongsheng extensions that are widely available, which work in some situations. Yes, we're DIYers, but still.

The second is with the DS-103 screen real estate. The biggest consumer of space is the IMO, dumb assist level graphic - that big inverted "J"-like swish in the middle:


Yeah, I want to know the assist level, but to me, the power draw is much more deserving of the display's real estate, as is the battery voltage. I don't yet trust the voltage graphic, after ignoring it on my Bafang bikes for so long. And, on my display, the voltage text value is 1.3 volts low. Admittedly I'm still getting used to this display.

The display's clock forgets the time not long after shutting off or disconnecting the battery, and the clock settings screen stupidly asked you to enter the year, month, day, and second - even though these values aren't displayed.

Whine, whine, whine.

 

[Mongo]

You are knowledgeable ncmired and want to ask, all said are you happy with your new Photon? Would you consider yourself a performance rider and touch 30 mph once in a while? Have you owned other Bafang products as a basis for comparison? No doubt the torque sensor is nice.

I'm NOT a performance or high-strength rider anymore - seventy, weak legs, overweight, and shot kidneys (but improving what I can). I've worked in bike shops and factories in the past, enjoy spokes-up "the way I want 'em" builds, and have too many e-bikes now (most of which are in the signature line) - e-bike builds being my retirement hobby. Some of the builds are thought experiments, honestly.

The only way I can readily exceed 30mph is with my Luna Lunacrous V2 controller builds. I don't like, or have not been able to get used to cadence-based riding, and am hoping that torque-sensing works for me and I end up less frustrated and instead, end up just throttling along instead. I should spend more time on the BBSHD's settings, toward what @AZeBikeGuy has come up with.

And then there's the air or ghost pedaling, err, umm, honesty.

However, I will still high-speed throttle when picking up the groceries on hot days, with the fast bikes - they also help keep me alive in busy traffic.

 

[Wattman]

Timing couldn't be better for seniors to have ebikes hitting the streets as we try to manage our loss in physical strength.
I am riding my ebikes a lot more now than acoustic bikes but also come from a motorcycle background and appreciate motor propulsion.
Do you have your Photon build out on the street yet ncmired?

 

[Mongo]

---

Timing couldn't be better for seniors to have ebikes hitting the streets as we try to manage our loss in physical strength.
I am riding my ebikes a lot more now than acoustic bikes but also come from a motorcycle background and appreciate motor propulsion.
Do you have your Photon build out on the street yet ncmired?

I rode motorcycles for about thirty years and also bicycle commuted, till I couldn't manage either anymore. I got so weak that I could barely walk the forty feet to the mailbox, on a level driveway, without falling over/passing out. Dialysis (and the other related stuff) ain't fun and is only partially effective - varies per individual. I've had a used kidney sewn in (twice) and am working on reducing tonnage - 90 lbs down so far, and another 70-90 lbs would be better.

The current Photon-powered bike is a bit of a specialty-purpose build (described here) and I'm awaiting some light wiring parts for it, so it's up on the repair stand right now. I've only got a handful of short rides on it so far, but have some torque-sense only, 20-30mile trail rides in mind to test it out properly. The CYC throttle has a clamshell design, and I intend to remove it for these rides - promise!

I believe in choosing the components for the package and ride intent - in this case a smaller outline (20" wheels), lighter weight bike to be ridden on mostly easier grade rails-to-trails terrain. The desired speeds are 10-15 mph torque-pedal-assisted and low to mid 20s mph sustained throttle, with peaks in the high twenties, if having to deal with short stretches of dense traffic. 30 mph is about the top speed this bike loaded down with gear, seems to be happiest with stability-wise, and that's more than fast enough for the intent.

Range, even lightly motor-assisted, is also part of the intent, and dropping the speeds doesn't hurt in that regard - especially if I have to push the battery to fumes. Out to 100 miles max over two days, I hope - 17-21AH battery capacity is my best initial guess.

Sound-wise, I've had a chance to listen to it, riding throttle only in the twenties, and with enough tailwind to reduce wind noise. I'd say the decibel level is between a stock BBS02 and a PEEK-geared, well broken in BBSHD (which is, for me, a VERY quiet motor). The sound quality is less gear-mesh-ish and more white-noise-ish.

The ass/saddle friendship is not a problem for the time & distance - the leg output is. But, I've got a few years to work on it.

---

I've got another CYC Photon on order, again to replace an existing BBS02 - this time on a loaner bike build for seniors (described here).

These seniors, in their sixties-seventies who haven't balanced a bicycle since they were a kid and haven't sat on a saddle in that long, have a hard enough time getting going - beyond trying to understand the complicated cadence power levels. I want to mellow down the power delivery and peaks, set the bike on level one or two, and send them on their way (hopefully, having fun, on a safe paved trail, with no walkers they can mow over). Via the app, I can give them more oomph, should they gain confidence and ability. But sorry - no throttle, at least not initially.

I know several e-bike curious old-timers, a few maybes, fewer I'll try it, but only one street-comfortable street-safe rider so far (BBS02 motor and MSF-trained). Given comfort levels and the right roads, I hope to convert a few more, at least. Keep the car, just use it less, when possible.

 

[hindesite]

On the rings, I've got a 38t currently, and an 34t motor on order for another project. The 38t I received has, I think, an aluminum gear ring - maybe the $50 difference.

I'm hoping Lekkie jumps in and offers more selection - both teeth and chain lines.

What is your assessment of the quality of the 38t? Does it appear better than my description of the 34t?

Hopefully CYC sell enough Photons to make Lekkie sit up and take an interest, maybe make improvements.

I might visit them with my Photon, they are just around the corner from where I live

 

[Mongo]

What is your assessment of the quality of the 38t? Does it appear better than my description of the 34t?

Hopefully CYC sell enough Photons to make Lekkie sit up and take an interest, maybe make improvements.

I might visit them with my Photon, they are just around the corner from where I live

Glad you asked, so I'd get up off my arse and take another look (and do a magnet test) - The ring is steel after all, and a magnet is easily drawn to the tip of a narrow tooth. It appears to be black anodized. To my old eyes, the machining looked consistent tooth to tooth, but not quite as clean and/or the edges as sharp as Lekkie's work - but Lekkie rings are aluminum. On my installation, the chainring fit to the carrier spline was a slightly tight slide, and the cover ring drew it down neatly, without fuss. I tried loosening up what looks to be the chainring to "spider" lockring with the CYC tool, but couldn't.

It would be nice if Lekkie jumped in - I wonder what kind of unit volume they need to make it worthwhile? What I'd like to see them attempt is:

1. a generic chainring BCD spider, with some degree of chain line adjustability. I can't tell easily now, but I doubt they could make a 4-hole 104 BCD spider that clears the motor secondary case and maintains the sweet 47mm minimum chain line (on a 68mm BB frame) - maybe 120 or 130 BCD would be possible
2. a few mid-thirties and forties chainrings with chain line adjustability out to approx. 58mm, for Sturmey Archer and Rohloff hub builds - yes, drive side BB spacers could be added with the stock 34T ring, but spacers look shoddy to me and screw up the Q
3. if CYC doesn't get around to it, a short spindle and a narrower lock ring specifically for 68-73mm BB builds, to narrow up the Q and for better looks - there's plenty of room between the left crank arm and the motor
4. for the nostalgic old timers like me - small runs of plain silver chainrings, cover rings, and crank arms

 

[Mongo]

There are some made-to-order custom bike frame builders out there with very well-heeled customers (kinda goes hand in hand) that have been interested in a quality, well-finished, lightweight, reliable, torque-sensing motor system they can fit in their existing and beloved 68mm English BBs, as an option.

I'm referring to the silver-brazed, hand-filed lug builder and consumer crowd here, with just-the-frameset pricing starting north of 3-4k - sometimes well north. The component aesthetics, fit, and finish are very important to these people.

They've not liked the Bosch system, mainly because of the integrated BB requirement I've heard - even though the power level and ride quality was appropriate. There are possibly some minimum purchase volume issues too. Some have tried the Tonsheng, but it's not up to the quality level they want and are willing to pay for.

The CYC Photon motor, with some options and cosmetic improvements, might just be what they're looking for.

 

[Atak_Snajpera]

Can you check "for science" how well torque sensor is calibrated in terms of calculating human pedaling power on assist level 0?

Here are some examples (flat surface and no wind)
20 km/h - ~75 W
25 km/h - ~120 W
30 km/h - ~200 W

 

[hindesite]

1. a few tooth count mid-thirties chainrings with chain line adjustability out to approx. 58mm, for 148 Boost, Sturmey Archer, and Rohloff hub builds - yes, drive side BB spacers could be added with the stock 34T ring, but spacers look shoddy to me and screw up the Q
2. if CYC doesn't get around to it, a short spindle and a narrower lock ring specifically for 68-73mm BB builds, to narrow up the Q and for better looks - there's plenty of room between the left crank arm and the motor

I can post some photos later, but the 34t as supplied matched the existing chainline on my bike, and it is 148 Boost. The Q is also exactly symmetrical using the recommended spacers with my 73mm BB, with none on the drive side. They are slightly wider of course so agree that some space could be saved. I guess CYC had to cover all bases and are only using one spindle for that reason and have been conservative with Q factor.

I'm extremely impressed with how the unit fits what has previously been a difficult frame to accommodate. CYC have done a fantastic job there.

Would like to see an option for a chunkier control unit with a simpler display - perhaps LCD or even just LEDs for battery level. I have little interest in how fast I'm going, Strava records that for me. The current one seems a bit fragile and I doubt would be easy to operate with gloves, the tactile feedback is minimal, and the M and ^ buttons are very close together.

 

[Mongo]

Can you check "for science" how well torque sensor is calibrated in terms of calculating human pedaling power on assist level 0?

Here are some examples (flat surface and no wind)
20 km/h - ~75 W
25 km/h - ~120 W
30 km/h - ~200 W

I'll try to give it a shot when conditions permit. A few differences may render the data hard to correlate are:

1. I ride upright and high drag, and the bike has a backpack on the front of it and 20" wheels
2. the CYC Photon only has three powered assist levels (1-3), at 0 the throttle and torque assist are disabled
3. yeah, I've mucked with the default power level settings.

I'll try anyway.

 

[Wattman]

I rode motorcycles for about thirty years and also bicycle commuted, till I couldn't manage either anymore. I got so weak that I could barely walk the forty feet to the mailbox, on a level driveway, without falling over/passing out. Dialysis (and the other related stuff) ain't fun and is only partially effective - varies per individual. I've had a used kidney sewn in (twice) and am working on reducing tonnage - 90 lbs down so far, and another 70-90 lbs would be better.

The current Photon-powered bike is a bit of a specialty-purpose build (described here) and I'm awaiting some light wiring parts for it, so it's up on the repair stand right now. I've only got a handful of short rides on it so far, but have some torque-sense only, 20-30mile trail rides in mind to test it out properly. The CYC throttle has a clamshell design, and I intend to remove it for these rides - promise!

I believe in choosing the components for the package and ride intent - in this case a smaller outline (20" wheels), lighter weight bike to be ridden on mostly easier grade rails-to-trails terrain. The desired speeds are 10-15 mph torque-pedal-assisted and low to mid 20s mph sustained throttle, with peaks in the high twenties, if having to deal with short stretches of dense traffic. 30 mph is about the top speed this bike loaded down with gear, seems to be happiest with stability-wise, and that's more than fast enough for the intent.

Range, even lightly motor-assisted, is also part of the intent, and dropping the speeds doesn't hurt in that regard - especially if I have to push the battery to fumes. Out to 100 miles max over two days, I hope - 17-21AH battery capacity is my best initial guess.

Sound-wise, I've had a chance to listen to it, riding throttle only in the twenties, and with enough tailwind to reduce wind noise. I'd say the decibel level is between a stock BBS02 and a PEEK-geared, well broken in BBSHD (which is, for me, a VERY quiet motor). The sound quality is less gear-mesh-ish and more white-noise-ish.

The ass/saddle friendship is not a problem for the time & distance - the leg output is. But, I've got a few years to work on it.

---

I've got another CYC Photon on order, again to replace an existing BBS02 - this time on a loaner bike build for seniors (described here).

These seniors, in their sixties-seventies who haven't balanced a bicycle since they were a kid and haven't sat on a saddle in that long, have a hard enough time getting going - beyond trying to understand the complicated cadence power levels. I want to mellow down the power delivery and peaks, set the bike on level one or two, and send them on their way (hopefully, having fun, on a safe paved trail, with no walkers they can hit). Via the app, I can give them more oomph, should they gain confidence and ability. But no throttle, at least not initially.

I've got a lot of e-bike curious old-timers, a few maybes, a few I'll try it, but only one street-comfortable street-safe rider so far (BBS02 motor and MSF-trained). Given comfort levels and the right roads, I hope to convert a few more, at least. Keep the car, just use it less, when possible.

You are quite knowledgeable and a lovely writer. Thanks for sharing your journey each of us are on as we each try and make the best of each day. When you get in the fourth quarter of the game, things come more into focus.
As I read about your health challenges, the thought that comes to mind is the adage, "hard to keep a good man down".
Lessor men crumble and give in, but not you which speaks to the strength of your mind and love of life. Motorcycle riders in particular have this in common I believe. There is a fellow in another thread by the name of Walley who just had another stroke and he is another soldier still building and riding ebikes because its what he likes to do. I presume there are more on this forum as well.
These ebikes keep us seniors in the game and we use our life long learning to navigate this wonderful technology.
Love all the projects you are working on and thanks for sharing your wisdom.

 

[Wattman]

There are some made-to-order custom bike frame builders out there with very well-heeled customers (kinda goes hand in hand) that have been interested in a quality, well-finished, lightweight, reliable, torque-sensing motor system they can fit in their existing and beloved English BBs, as an option.

I'm referring to the silver-brazed, hand-filed lug builder and consumer crowd here, with just-the-frameset pricing starting north of 3-4k - sometimes well north. The component aesthetics, fit, and finish are very important to these people.

They've not liked the Bosch system, mainly because of the integrated BB requirement I've heard - even though the power level and ride quality was appropriate. There are possibly some minimum purchase volume issues too. Some have tried the Tonsheng, but it's not up to the quality level they want and are willing to pay for.

The CYC Photon motor, with some options and cosmetic improvements, might just be what they're looking for.

I have a penchant for foo-foo bicycles as well but another side of me wants power to stay up with elite road cyclists. I am a speed guy who still pedals hard. So aesthetics is subordinate to speed for me and I would be saying 'on your left' to the brazed lug crowd on their vintage retro works of art with their commensurate mild Photon motor as I roll by.
I will tell what having 1700 watts exposes. Nationally ranked cyclists have nothing on an old fit rider with a BBSHD. I have had the fastest cyclists in my town hold my wheel at 30 mph and afterword, we have a good laugh about it.
I am not into the half pregnant strategy however of Sur-Ron powered e-bike or e-motorcycles. I want gas and the open road with a license plate on the back for 50+ mph riding on two wheels.
Some further musings from a guy who has spent a lot of time on two wheels mixing it up with a lot of different kind of riders.

 

[Mongo]

I can post some photos later, but the 34t as supplied matched the existing chainline on my bike, and it is 148 Boost. The Q is also exactly symmetrical using the recommended spacers with my 73mm BB, with none on the drive side. They are slightly wider of course so agree that some space could be saved. I guess CYC had to cover all bases and are only using one spindle for that reason and have been conservative with Q factor.

I'm extremely impressed with how the unit fits what has previously been a difficult frame to accommodate. CYC have done a fantastic job there.

Would like to see an option for a chunkier control unit with a simpler display - perhaps LCD or even just LEDs for battery level. I have little interest in how fast I'm going, Strava records that for me. The current one seems a bit fragile and I doubt would be easy to operate with gloves, the tactile feedback is minimal, and the M and ^ buttons are very close together.

Wait - the 34T and 38T chainrings have different chain lines? With my 38T chainring and a 68mm BB, I roughly measured a 47mm chain line (with no drive line spacers, so I could hit the Shimano Alfine 48mm "dished sprocket out" chain line), and this measurement synced up pretty well with the current CYC user manual chain line / spacer arrangement table on page 15 (68mm BB, 50.3 with a 3mm drive side spacer, 47.3mm without). Here's that chart:

Is your chain line 49.8mm then, or wider, with the 34T? I've not done a boost build and I've no working experience with the related spacing numbers - I thought 148 Boost required a "pretty far out there" chain line.

I ask, as my second Photon build also needs a 50-ish or tighter chain line (on a 73mm BB) - so I was thinking I was going to end up at 50.3mm. Yep, I assumed that the chain line was equal for all three Photon chainrings, and even stuck an uncalibrated but fat finger in between my 38T chainring inside dimension and the motor casting pinion bump-out.

I forgot to add the (lack of) display choices to my wish list, and I've already poo-pooed the DS103 model, as currently programmed. I think I'd prefer a landscape/horizontal orientation display with a USB port.

 

[Atak_Snajpera]

I'll try to give it a shot when conditions permit. A few differences may render the data hard to correlate are:

1. I ride upright and high drag, and the bike has a backpack on the front of it and 20" wheels
2. the CYC Photon only has three powered assist levels (1-3), at 0 the throttle and torque assist are disabled
3. yeah, I've mucked with the default power level settings.

I'll try anyway.

Check this calculator.

Cycling Wattage Calculator

If you're curious about what power you produce while cycling and how it depends on your position, speed, or even tire type, give this cycling wattage calculator a try! 🚴

www.omnicalculator.com

Remember to use assist level 0.

btw. I'm asking Because my stealth gen1 with bac855 on default settings (69nm/volt) was overestimating my pedaling power 6 times!

 

[Mongo]

Check this calculator.

Cycling Wattage Calculator

If you're curious about what power you produce while cycling and how it depends on your position, speed, or even tire type, give this cycling wattage calculator a try! 🚴

www.omnicalculator.com

Remember to use assist level 0

Oh, ok - I think I see what you're looking for now - sorry 'bout that.

 

[Mongo]

I have a penchant for foo-foo bicycles as well but another side of me wants power to stay up with elite road cyclists. I am a speed guy who still pedals hard. So aesthetics is subordinate to speed for me and I would be saying 'on your left' to the brazed lug crowd on their vintage retro works of art with their commensurate mild Photon motor as I roll by.
I will tell what having 1700 watts exposes. Nationally ranked cyclists have nothing on an old fit rider with a BBSHD. I have had the fastest cyclists in my town hold my wheel at 30 mph and afterword, we have a good laugh about it.
I am not into the half pregnant strategy however of Sur-Ron powered e-bike or e-motorcycles. I want gas and the open road with a license plate on the back for 50+ mph riding on two wheels.
Some further musings from a guy who has spent a lot of time on two wheels mixing it up with a lot of different kind of riders.

Thanks very much for the kind compliments. I wouldn't say I'm a good man (as some would define it), and yeah, healthwise I've been through the wringer. But, during all the time I spent in/on hospital wards, there was almost always somebody else there having a helluva worse time than I was. Or say, one day, listening to an ER doctor a closed curtain away telling a guy his crash injury is very serious, and having to delicately dance around the quadriplegic subject.

I like the speed sensation too, but have backed off - my current reaction skills aren't up to it, and honestly never where. Now, when riding on trails and away from traffic, I like poking and just gliding along, averaging 15-20mph or so. I usually let the strong analog trail riders pass me by - they're earning it I figure. Sometimes I lay back aways and pace them, just to get an idea of their speeds, then let 'em go and save battery. I save my high speeds for when errand running in dense traffic.

Yep, I'm a lugged frame sucker and particularly love the chrome and half-lugged look and craftsmanship of the Chapman custom frames.

My two fast bike builds are real pigs, mostly because of the batteries, and I'd hate to have to just analog pedal them. They were built to be reliable, strong, fast, and stable when heavily loaded - there's a grey, "still a bicycle / not really a bicycle" crossover point, and maybe these particular builds cross over too far. Oh well.

 

[Wattman]

Thanks very much for the kind compliments. I wouldn't say I'm a good man (as some would define it), but yeah, healthwise I've been through the wringer. But, during all the time I spent in/on hospital wards, there was almost always somebody else there having a helluva worse time than I was. Or say, listening to an ER doctor a closed curtain away telling a guy his crash injury is really bad, and having to delicately dance around the quadriplegic subject.

I like the speed sensation too, but have backed off - my current reaction skills aren't up to it, and honestly never were. I dabbled in and around race boats (APBA utility runabout, B and GNH hydroplane) for a while, too. Now, when riding on trails and away from traffic, I like poking and just gliding along, averaging 15-20mph or so. I usually let the strong analog trail riders pass me by - they're earning it I figure. Sometimes I lay back aways and pace them, just to get an idea of their speeds, then let 'em go and save battery. I save my high speeds for when errand running in dense traffic.

Yep, I'm a lugged frame sucker and particularly love the chrome and half-lugged look and craftsmanship of the Chapman custom frames. My fast bike builds are real pigs, mostly because of the batteries, and I'd hate to have to just analog pedal them - there's a grey, "still a bicycle" crossover point, and maybe these particular builds cross over too far. Oh well.

Important point is you get the hobby and many haven't a clue. I look forward to you sharing your builds on the forum if you care to.
In particular there is a lot of buzz about the Photon motor. For me personally, I am more interested in what is anticipated which is a higher power big brother of the Photon....may be called the Proton. I likely would have built with the big boy CYC because I like power but I can't stand a loud sound signature when riding an e-bike. As you and others have reported, the Photon is quiet like the BBSHD which is a major win and here-to-fore the achilles heel of CYC. Best of luck with your health and ebike pursuits.

 

[hindesite]

Wait - the 34T and 38T chainrings have different chain lines? With my 38T chainring and a 68mm BB, I roughly measured a 47mm chain line (with no drive line spacers, so I could hit the Shimano Alfine 48mm "dished sprocket out" chain line), and this measurement synced up pretty well with the current CYC user manual chain line / spacer arrangement table on page 15 (68mm BB, 50.3 with a 3mm drive side spacer, 47.3mm without). Here's that chart:
Is your chain line 49.8mm then, or wider, with the 34T? I've not done a boost build and I've no working experience with the related spacing numbers - I thought 148 Boost required a "pretty far out there" chain line.

I ask, as my second Photon build also needs a 50-ish or tighter chain line (on a 73mm BB) - so I was thinking I was going to end up at 50.3mm. Yep, I assumed that the chain line was equal for all three Photon chainrings, and even stuck an uncalibrated but fat finger in between my 38T chainring inside dimension and the motor casting pinion bump-out.

I happen to measure (before I saw your figures) chainline for the 34t at 50.3mm on 73mm BB with no drive side spacers. That's close enough.

I think Boost 148 for MTB chainljne is around 51mm, which ties in with CYC offset. Previous setup was DUB NX but I suspect the LBS didn't look up the correct spacing when they did the install of that system and it was about 1.5mm further out (plus it had failed at <1,000km prob due to wrong preload). So chainline has probably improved by fitting the Photon.

I think Boost only moves about 3mm outward from standard, which ties in with your chainline with the 38t. It's fair to assume CYC don't think 38t will be fitted to Boost frames which might be why the chainline is different.

 

[Mongo]

I happen to measure (before I saw your figures) chainline for the 34t at 50.3mm on 73mm BB with no drive side spacers. That's close enough.

I think Boost 148 for MTB chainljne is around 51mm, which ties in with CYC offset. Previous setup was DUB NX but I suspect the LBS didn't look up the correct spacing when they did the install of that system and it was about 1.5mm further out (plus it had failed at <1,000km prob due to wrong preload). So chainline has probably improved by fitting the Photon.

I think Boost only moves about 3mm outward from standard, which ties in with your chainline with the 38t. It's fair to assume CYC don't think 38t will be fitted to Boost frames which might be why the chainline is different.

@hindesite, thanks much for the chain line measurement - whew, I was concerned!

 

[hindesite]

Fitting Photon to a frame with ISCG tabs

If your bike frame has ISGC tabs, you'll need to modify them before fitting the motor. This isn't difficult, you'll need a hacksaw and file. Pics below.

Since my frame (Silverback Slade Trail) has ISCG tabs, clearance had to be made for the motor. Sad, but had to be done. Easy to mark out and since the frame is aluminium, easy to cut by hand and file to a clean finish.

First guess for the cut turned out great – about 12mm from the inside face of the housing, and as it turns out, pretty much perpendicular to the chainstays. The motor fits within about 3mm of the downtube, which is as high as possible.

Not worth painting the cut, since it is not visible or exposed once the motor is fitted. I usually just touch up with a black marker for appearances.

The Photon has a fillet where the motor body joins the gear casing, so the ISCG plate had to be cut to clear this. However it is really important that the motor never rotates so that the corners of the cut ISCG plate might damage the motor casing.

BTW, there is enough room between the motor casing and the BB collar to allow fairly large tools to fit.

I haven't found a way to anchor the motor casing against the downtube (which CYC give a warning about in their manual, maybe to CTAs) so I used some carbon grip paste on the drive side face, and it seems pretty secure; can anyone comment on their installation and how they anchored the motor, or any issues if they didn't?

 

[Mongo]

Though I had concerns when I saw that CYC choose not to anchor the motor firmly, I haven't had or noticed any turning or motor movement. During the install, I butted the motor up against a cable stop screwed into one of the down tube water bottle bosses.

I did buy an $8 open-ended cup wrench, so that I could check the spindle cup tightness without having to remove the crank arm.

I didn't install any of the three spacer blocks (68mm BB install), choosing instead to just use some shortened M4 screws to hold the plate to the motor.

 

[hindesite]

Though I had concerns when I saw that CYC choose not to anchor the motor firmly, I haven't had or noticed any turning or motor movement. During the install, I butted the motor up against a cable stop screwed into one of the down tube water bottle bosses.

I did buy an $8 open-ended cup wrench, so that I could check the spindle cup tightness without having to remove the crank arm.

I didn't install any of the three spacer blocks (68mm BB install), choosing instead to just use some shortened M4 screws to hold the plate to the motor.

Fair enough, but it is a good place to keep the spare spacers in case you move to a different BB The supplied screws could be better quality.

The grip paste seems to be doing a pretty good job and has to be better than nothing, I had also considered using adhesive/sealant.

 

[pxl666]