Grin V3 All Axle Torque Arm Fitting Question

[Niner63]

Hi everyone

I’ve been saving my $$$ for a while now and would like to fit a V3 All Axle to my Boost Adventure bike.

Having spent some time reading the V3 owners manual I’m concerned that I might run into trouble fitting the torque arm to my chain stay.
I am a little confused by Grins “Important” notice and suggested use of “spacers” or repositioning the hardware.

“Important: if your frame geometry does not allow the torque arm to sit flat on the plate, then use spacers or reposition hardware so that it does.
Do not force the arm to flex in or out, as this may put unnatural stress concentrations”

My chain stay is curved and I’m worried I’ll have issues fitting the torque arm to the chain stay.

I‘d greatly appreciate any help, suggestions on whether you believe that the torque arm will fit my bike and or how and where to use ”spacers” to make it fit.

The bike is currently running 29” 2.5” tyres, though could run narrower tyres in 29” or 27.5”

Hopefully I’m simply overthinking it and a V3 AA kit will fit aok.

Thanks in advance everyone


The second picture is my bike chain stay, with approx dimensions shown

 

[99t4]

If the spacers are not able to get the TA clamping pad lined up properly on the stay, you should be able to slightly bend the arm (while it is not mounted to the motor) so that it aligns into position when mounted.

A bench vise would be handy. Might take several iterations.

The main issue is to avoid having to force the arm in/out to line up while mounted to the motor. When clamped to the stay the arm should be in a "neutral" position, not forced into place.

Grin tech support should be responsive to your inquiries. Have you sent them your photos to see if they have suggestions?

 

[amberwolf]

I am a little confused by Grins “Important” notice and suggested use of “spacers” or repositioning the hardware.

“Important: if your frame geometry does not allow the torque arm to sit flat on the plate, then use spacers or reposition hardware so that it does.
Do not force the arm to flex in or out, as this may put unnatural stress concentrations”

My chain stay is curved and I’m worried I’ll have issues fitting the torque arm to the chain stay.

What it means is that the arm is designed to work in a specific way.

If it can't be mounted in that way, it may not operate as designed, and the torque transfer from axle to frame it is intended to do may not happen, or not correctly, and this may damage the axle, the frame, the arm, etc. and allow the motor axle to spin in the dropouts and damage the wiring, etc.

As long as the arm is not flexed, which puts twisting or tension along the arm, and the frame-mounting-end can correctly fit into the frame-mounted support and be fixed in place in a way that transfers the torque to the frame as designed, and the axle-mounting-end can correctly fit onto the axle adapter so that adapter can correctly transfer the axle torque to the arm itself, it should work.

If you have to flex it (such as by affixing the axle end and then forcing the frame end inward to the frame moutning piont, bolting it down, then removing whatever you used to flex it), then you leave tensions on the hardware that arent' accounted for in the design, and may cause a failure at some point.

For instance, it could put enough stress on the screws that connect the arm to the axle hardware to eventually fracture their heads and allow the arm to come off the axle hardware, completely or partially, and the axle could then spin (which should never happen). Or it oculd put enough stress on the frame mounting hardware that it twists around the frame and becomes able to rock back and forth (which should never happen).


You might be able to permanently bend the arm at some point between the two mounting ends to match the frame shape, and that won't leave a tension. You would probably need to do two bends--one near the middle of the arm to start the bend that matches the frame shape, and one near the frame-moutning-end to re-align that end with the frame mount hardware.




On the GMAC, which has similar torque arm hardware, I was able to mount it "straight on" on my SB Cruiser trike, because my frame rails are straight over the top of the axle. But if I had the old framework the trike started with, I'd've had to pre-bend the arm somewhere past the axle end to match the angle of the old framework to get it to all line up correctly and not put unaccounted-for stresses on the parts.

 

[Niner63]

What it means is that the arm is designed to work in a specific way.

Thank you amberwolf, for your detailed reply.
Having read the V3 AA owners manual I was aware that any undue lateral forces, upon fitting le torque arm, was beyond manufacturing specifications with the potential for failure catastrophique.
As 99t4 suggested, I’ll now contact Grin directly regarding the chain stay mounting hardware, spacers and if they believe if it would be possible/advisable to “preform“ the torque arm to fit, without any excess lateral forces, to my bike and chain stay.

 

[Niner63]

If the spacers are not able to get the TA clamping pad lined up properly on the stay, you should be able to slightly bend the arm (while it is not mounted to the motor) so that it aligns into position when mounted.

A bench vise would be handy. Might take several iterations.

The main issue is to avoid having to force the arm in/out to line up while mounted to the motor. When clamped to the stay the arm should be in a "neutral" position, not forced into place.

Grin tech support should be responsive to your inquiries. Have you sent them your photos to see if they have suggestions?

Merci 99t4 I’ll make contact with Grin customer support for more advice and about possibly “preforming” the torque arm to fit the chain stay mounting hardware to prevent excessive lateral forces

 

[Niner63]

Ok, so I just heard back from Grin, faster than I thought @ +36hrs, and they do not advise preform bending the torque arm to fit and for me that appears to be the end of road for any possible Grin conversion on this bike

The good news is that, while waiting for Grins reply, I started researching CYC Photon Gen 1 and the soon to be released Gen 2 mid drive motors and I’m hopeful that one of their 38T Gen 2 Photons will fit this bike

I’ll be printing a Photon fitment template tomorrow

 

[neptronix]

hhmm... there is a decent amount of adjustability on this torque arm in the x/y/z axis... i've fit it to a few bikes by now.. i'd be surprised if it wasn't adaptable to a bike, given that it doesn't have a super wild shape.

You could connect this to either the seat stay or chain stay.

 

[lnanek]

Yeah, don't the various installation demo videos have exactly that situation where the chain/seat stay curves in immediately and the torque arm just sits underneath it instead of alongside it?

Doesn't seem like a big issue.

I have a dozen different pipe and conduit clamps that can easily position a bolt next to a tube and even pivot around that bolt as a pivot point to cancel out the bend. So it would be easy to pipe clamp the chain and seat stay, pop a 90 degree angle bracket in there and have a parallel structure to bolt to that is further out if needed - but doesn't seem needed in this case.

Heck, sometimes I even build little triangles out of mending plates sticking out the back for supporting longer racks on my acoustic bike:


So nothing even says the torque arm has to be facing forward instead of, say, clamped to a straight pipe or mending plate that is sticking out the back, and that pipe is clamped to the straight part of your chain stay at the axle and right before the bend.

 

[Niner63]

hhmm... there is a decent amount of adjustability on this torque arm in the x/y/z axis... i've fit it to a few bikes by now.. i'd be surprised if it wasn't adaptable to a bike, given that it doesn't have a super wild shape.

You could connect this to either the seat stay or chain stay.

Yeah, don't the various installation demo videos have exactly that situation where the chain/seat stay curves in immediately and the torque arm just sits underneath it instead of alongside it?

Thanks guys

while I like to say “never say never”

I‘m waiting on CYC tech support to get back to me regarding the Gen 2 Photon.

My first choice for this bike always had been a Bafang or Tongsheng mid drive but neither would fit easily to give a good chainline.

When I first started researching mid drive motors the Photon had been out of my, then, price bracket.

The Photon Gen 2 is currently at the top of the list for this bike atm as I’ve been saving my $$$

I have an older steel Gravel bike, with an EBB, that could be Grin’d in 3 different flavors, with relative ease, listed below in order of preference, that I would also like to convert after completing my Ti conversion.

​

• Forcellina cargo fork, 20” front hub motor conversion, with a FH/212 or an eZee regen, matched to a Alphine 8 IGH. The Forcellini is Italian and available within the EU without import Taxes unlike the Clydesdale cargo fork.
• Gmac
• V3 All axle

The FW cargo fork conversion would also allow me to use my Coho trailer without the Gmac loosening the Burley Ballz axle mounted trailer hitches. The V3 AA is not suitable for the Coho trailer with qr through axles.

Where as my Ti bike is already fitted with a Burley Ballz through axle.

• 

 

[99t4]

they do not advise preform bending the torque arm to fit

I did not perceive that from their response you shared.

They were just repeating that the TA arm should not be bent in any way, I read that as not having the TA arm stressed in any direction to align the clamp to the stay.

You should be fine pre-bending the TA arm as necessary to get the clamp to line up, while remaining neutral at the axle mount. It is usually a matter of a few degrees, people do it all the time with no problems.

 

[Niner63]

I did not perceive that from their response you shared.

They were just repeating that the TA arm should not be bent in any way, I read that as not having the TA arm stressed in any direction to align the clamp to the stay.

You should be fine pre-bending the TA arm as necessary to get the clamp to line up, while remaining neutral at the axle mount. It is usually a matter of a few degrees, people do it all the time with no problems.

we often interpret and understand things differently based upon our beliefs and experiences, for me there are too many red flags in the Grin response including

“You will need to ensure the torque arm is not bent in any way”

post #9 details how I’m hoping to move forward with my 1st ebike conversion to build as clean a build as possible

 

[Niner63]

hhmm... there is a decent amount of adjustability on this torque arm in the x/y/z axis... i've fit it to a few bikes by now.. i'd be surprised if it wasn't adaptable to a bike, given that it doesn't have a super wild shape.

Yeah, don't the various installation demo videos have exactly that situation where the chain/seat stay curves in immediately and the torque arm just sits underneath it instead of alongside it?

I did not perceive that from their response you shared.

They were just repeating that the TA arm should not be bent in any way, I read that as not having the TA arm stressed in any direction to align the clamp to the stay.

You should be fine pre-bending the TA arm as necessary to get the clamp to line up, while remaining neutral at the axle mount. It is usually a matter of a few degrees, people do it all the time with no problems.

Justin from Grin has joined the conversation and clearly believes that the V3 All axle motor and torque arm would not be “tricky” to fit my Ti bike

Which is great news and confirms 99t4’s, Inanek’s and neptronix’s views that the V3 All axle will fit my bike, thank you guys

I’m still waiting on CYC’s Tech support to get back to me regarding their Gen 2 Photon mid drive, which still remains as my 1st choice for this particular build, though because of Justin’s email the V3 All axle is back on the cards as an option.

 

[E-HP]

Ok, so I just heard back from Grin, faster than I thought @ +36hrs, and they do not advise preform bending the torque arm to fit and for me that appears to be the end of road for any possible Grin conversion on this bike

The good news is that, while waiting for Grins reply, I started researching CYC Photon Gen 1 and the soon to be released Gen 2 mid drive motors and I’m hopeful that one of their 38T Gen 2 Photons will fit this bike

I’ll be printing a Photon fitment template tomorrow

View attachment 372918

Not sure why you need to try to make it work as-is, when we do DIY solutions here. Go down to the hardware store and but a solid corner bracket, replacer the little angle piece they are using with the corner bracket after drilling mounting holes (or get one with slotted holes) to get proper alignment.
Or, you can get off the shelf stuff to adapt to make a chain stay anchoring point (I adapted a mirror mount since the inner diameter matched my chain stay diameter).
It’s not a difficult problem unless you restrict yourself to in the box thinking.

Why again do you think the curved chanstay is an issue? It looks Lo pike it will work as-is, since the little angle piece can adjust/rotate to align it.

 

[Niner63]

Not sure why you need to try to make it work as-is, when we do DIY solutions here.

Hi E-HP

Post #1 explained my concerns regarding whether the Grin V3 would fit as Grin designed it to fit as is, or as it was designed to fit and work without any modifications or fabrication.

Following 99T4‘s advice and amberwolfs replies in posts #2 and #3 I decided to contact Grin tech support for further advice.

In post #6 I explained that Miguel from Grin tech support believed that the installation would be “tricky” and that I might consider fitting a mid drive motor. And how Id been researching the CYC Photon mid drive while I had been waiting for Grin to reply to my inquiry.

In posts #7 and #8 both neptronix and Inanek explained that they both believed that the Grin torque arm mounting bracket would, most likely, be able to accommodate my frame without putting any lateral strain on the torque arm and or hub motor.

In post #9 I replied to both neptronix and Inanek letting them know that I was waiting on CYC tech support to reply to my inquiry regarding the CYC Photon as mid drive motors had been my first choice for this conversion and how my previous research of cheaper mid drive motors had led to very likely and an undesirable chain line while using the cheaper, easily available, mid drive conversion kits due to my bikes drive side chain stay and how, at that time, my budget wouldn’t stretch to a CYC Photon mid drive kit. Plus my plans to convert a steel bike into a cargo fork front wheel kit using off the shelf parts.

In post #12 I let neptronix, 99T4 and amberwolf that know Justin from Grin had emailed me saying that he didn’t believe that the V3 would be “tricky” to fit my bike but I was still waiting to hear from CYC tech support because of the reasons listed above, see post #9

From Justins reply from Grin, today, it’s evident that it would be very unlikely that I would need to use hardware store corner brackets to adapt Grins torque mounting bracket to secure the V3 torque arm to my bike, should I decide to use their V3 off the shelf conversion kit.

I‘m sorry I’m not as clued up as you are when it comes to diy e-bike conversions and that I don’t always immediately understand the information that kit suppliers post on their websites and or the videos they share to help people like myself with little to no experience in e-bike conversions or DIY skills.
I joined this Forum to post questions that might ultimately help me from placing expensive orders and paying high import taxes for a diy kit that might not be applicable to my needs. And hopefully for others in similar situations being able to see if an off the shelf diy kit will work for their donor bike conversion while they’re using an internet search and come across links to this and other diy ebike related forums

​

️​

 

[neptronix]

Here's some thoughts for you:

- do you need the power and regenerative abilities of the all axle? if not, you might wanna consider a shengyi sx2 and a single torque arm. This is the most efficient small to mid size motor grin has on offer and it should easily take 1250w peaks and be lighter. It's also a lot cheaper.

- i'm personally unconvinced that the all axle couldn't work. The solution may or may not involve a drill and a trip to the hardware store.

- downside of the CYC will be a very wide pedaling stance that can't be changed. I'd recommend riding a fatbike and seeing if your legs like it if you haven't. I am not the only person on this forum whose legs have a hard time with this biomechanically challenged pedaling situation.

The answer to this depends on your physical build. Humans come in a variety of widths. I'm built more like the asian fellow than the tongan warrior... so any bike with 200mm Q factor is not for me.

 

[Niner63]

Here's some thoughts for you:

- do you need the power and regenerative abilities of the all axle? if not, you might wanna consider a shengyi sx2 and a single torque arm. This is the most efficient small to mid size motor grin has on offer and it should easily take 1250w peaks and be lighter. It's also a lot cheaper.

- i'm personally unconvinced that the all axle couldn't work. The solution may or may not involve a drill and a trip to the hardware store.

- downside of the CYC will be a very wide pedaling stance that can't be changed. I'd recommend riding a fatbike and seeing if your legs like it if you haven't. I am not the only person on this forum whose legs have a hard time with this biomechanically challenged pedaling situation.

The answer to this depends on your physical build. Humans come in a variety of widths. I'm built more like the asian fellow than the tongan warrior... so any bike with 200mm Q factor is not for me

Thank you neptronix

my Ti bike is a 12mm through axle hence why I considered the all axle and not the sx2 for this build, after realising that the more budget mid drives would not fit and or give a good chain line.

Since October, last year, when my Specialized Vardo 4 died after 3 years of hard riding, I decided it was uneconomical to repair it and I’ve been riding my Ti bike sans electric power since then.
During this time it’s become evident that, as I’m fast approaching 60, my asthma has gotten much worse. Sprinting and or prolonged effort while climbing hills can trigger acute asthma attacks.

I don’t own, or want to own a car again just yet.

Because of my asthma I’ve found myself riding much less than I had with my Vado, or before I bought my Vado, and I would like a more powerful ebike so that I can get out more often and do the 30-40 km round trips that I used too and occasional 60 km trips to visit family without resorting to car hire without trigger my asthma.

@ 6’ 6” I’m not too concerned about a wide Q factor.

Justin from Grin emailed me this morning and he believes that the all axle torque arm mounting kit will fit my Ti bike without any modification, see post #12 about Justins email.

I’ve spent some time today researching options to convert my steel gravel bike to a 20” front wheel drive cargo fork, grocery getter, do it all, short trip +- 16km bike that I’d be riding 3 or 4 times a week and use the Ti bike 2 or 3 times a week, for longer and more challenging rides.

 

[E-HP]

Hi E-HP

Post #1 explained my concerns regarding whether the Grin V3 would fit as Grin designed it to fit as is, or as it was designed to fit and work without any modifications or fabrication.

Following 99T4‘s advice and amberwolfs replies in posts #2 and #3 I decided to contact Grin tech support for further advice.

In post #6 I explained that Miguel from Grin tech support believed that the installation would be “tricky” and that I might consider fitting a mid drive motor. And how Id been researching the CYC Photon mid drive while I had been waiting for Grin to reply to my inquiry.

In posts #7 and #8 both neptronix and Inanek explained that they both believed that the Grin torque arm mounting bracket would, most likely, be able to accommodate my frame without putting any lateral strain on the torque arm and or hub motor.

In post #9 I replied to both neptronix and Inanek letting them know that I was waiting on CYC tech support to reply to my inquiry regarding the CYC Photon as mid drive motors had been my first choice for this conversion and how my previous research of cheaper mid drive motors had led to very likely and an undesirable chain line while using the cheaper, easily available, mid drive conversion kits due to my bikes drive side chain stay and how, at that time, my budget wouldn’t stretch to a CYC Photon mid drive kit. Plus my plans to convert a steel bike into a cargo fork front wheel kit using off the shelf parts.

In post #12 I let neptronix, 99T4 and amberwolf that know Justin from Grin had emailed me saying that he didn’t believe that the V3 would be “tricky” to fit my bike but I was still waiting to hear from CYC tech support because of the reasons listed above, see post #9

From Justins reply from Grin, today, it’s evident that it would be very unlikely that I would need to use hardware store corner brackets to adapt Grins torque mounting bracket to secure the V3 torque arm to my bike, should I decide to use their V3 off the shelf conversion kit.

I‘m sorry I’m not as clued up as you are when it comes to diy e-bike conversions and that I don’t always immediately understand the information that kit suppliers post on their websites and or the videos they share to help people like myself with little to no experience in e-bike conversions or DIY skills.
I joined this Forum to post questions that might ultimately help me from placing expensive orders and paying high import taxes for a diy kit that might not be applicable to my needs. And hopefully for others in similar situations being able to see if an off the shelf diy kit will work for their donor bike conversion while they’re using an internet search and come across links to this and other diy ebike related forums

​

️​

It’s only tricky if you restrict yourself to the box. They want the arm to be straight because they thinned it out the width so much to save weight that it needs to be straight or the strength is compromised. The angle piece that it attaches to the anchor doesn’t provide enough offset (arguable until you try test fitting), so fabricating a piece will allow for that ( or getting something off the shelf in a hardware store). Grin isn’t going to tell you to go to the hardware store, so yes or perhaps the stock part won’t work. This is a simple problem.

 

[99t4]

people like myself with little to no experience in e-bike conversions or DIY skills

It's OK. Looks like you are needing clear precise step-by-step instructions where a DIY build presents numerous gray areas requiring judgement calls based on experience and industry best practices. Sometimes what we here see as simple processes are not always understood by others as self-evident.

 

[neptronix]

6'6, say no more. You'd probably like the CYC.

The all axle motor is an excellent fit for a 20" wheel and can produce insane amounts of speed/torque given adequate voltage/amperage shot into it. I wouldn't bother with a mid drive for a small wheeled bike because the motor is always ready for hill climbing

I would not put a hot rodded all axle motor on a front wheel though.

 

[Niner63]

It’s only tricky if you restrict yourself to the box. They want the arm to be straight because they thinned it out the width so much to save weight that it needs to be straight or the strength is compromised. The angle piece that it attaches to the anchor doesn’t provide enough offset (arguable until you try test fitting), so fabricating a piece will allow for that ( or getting something off the shelf in a hardware store). Grin isn’t going to tell you to go to the hardware store, so yes or perhaps the stock part won’t work. This is a simple problem.

E-HP There is NO problem with fitting the V3 right out of the box, there is no need to think outside of the box……in this case.

As confirmed by Justin today by email as I have already explained to you before…..

Quote = “HI Ian, I don't see anything tricky about installing the motor on that frame. Our rear frame clamp has a huge amount of left/right sliding capability to position itself on the same plane as the torque arm regardless of how much your chainstays angle in or out of the dropout plane. Earlier designs were a bit more constrained but the one we are shipping with now has been vetted with a huge range”

 

[Niner63]

It's OK. Looks like you are needing clear precise step-by-step instructions where a DIY build presents numerous gray areas requiring judgement calls based on experience and industry best practices. Sometimes what we here see as simple processes are not always understood by others as self-evident.

Thank you 99t4, I don’t think I’ll need step by step instructions, some gentle hand holding is more than welcome though
I was simply concerned when I double checked the chain stays before ordering the all axle and like to reassured before dropping those kinda $$$ on a kit that I wasnt sure would fit.
I was then concerned about the advice given here about pre-bending and forming the torque arm. I followed your advice to contact Grin.

Then Miguel, from Grin suggested fitting a mid drive because he believed fitting the all axle would be “tricky”

This mornings email from Justin at Grin was a pleasant surprise

 

[Niner63]

6'6, say no more. You'd probably like the CYC.

The all axle motor is an excellent fit for a 20" wheel and can produce insane amounts of speed/torque given adequate voltage/amperage shot into it. I wouldn't bother with a mid drive for a small wheeled bike because the motor is always ready for hill climbing

I would not put a hot rodded all axle motor on a front wheel though.

I have considered a RH1212 but will more likely plump for a more budget friendly build as the Ti build will swallow a fair few $$$

 

[ZeroEm]

tongan warrior here, Niner63 don't sweat it. you need help adapting anything, your in the right place. We like makeing everything from scratch. If you noticed we like Grin because they started doing what you are doing and have been at it for a while. There all axel motor is tried and true. Hard to beat it for the size, weight and power. Some like the leafmotor has more power but is heaver. The RH1212 is great for the torque but you give up the speed.

It all depends on what you want so take time to figure it out. You have a light bike so weight should be important.

 

[Niner63]

tongan warrior here, Niner63 don't sweat it. you need help adapting anything, your in the right place. We like makeing everything from scratch. If you noticed we like Grin because they started doing what you are doing and have been at it for a while. There all axel motor is tried and true. Hard to beat it for the size, weight and power. Some like the leafmotor has more power but is heaver. The RH1212 is great for the torque but you give up the speed.

It all depends on what you want so take time to figure it out. You have a light bike so weight should be important.

Thank you

The CYC Photon is most likely going on the Ti
The FH1212 looks great on the simulator for my planned steel grocery getter, do it all, cargo fork Gravel bike, where torque over speed is required.
Im not sure if there’s much or any difference between the FH and RH 1212s

 

[Niner63]

Grin All Axle, Phaserunner and Cycle Analyst on route to be paired with a EM3ev 13s4p