Photon Gen 2 Retrofit on Trike with 3D Printed Parts

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I was going to add this to the end of the CYC Photon Gen 2 thread but that thread is already huge! Even describing this will require several posts.

Some 3D printed parts have been designed, prototyped and fitted to a 2008 vintage TRICE QNT trike to facilitate a Photon Gen 2 retrofit. Last year the trike was fitted with the Gen 1. I am seeking reduced thermal power limiting with the Gen 2 for climbing the Niagara Escarpment. Even though this is an installation for a specific trike, I think there are a few ideas that could be applied to any bike install and even more that could be applied to other trikes. 3D models (e.g. STEP) of any or all of the items designed can be supplied on request.

Anti-Rotation Plate

A "mid drive" (crank drive) like the Photon is mounted to the BB on the front of a trike. The reaction torque of a crank drive can be resisted by the derailleur post on a trike similar to on a diamond frame but the angle of this post locates the motor above the boom and with more overhanging mass. It is much better in my opinion to employ an anti-rotation device to locate the motor on the underside. This frees up the derailleur post for other things (e.g. lighting) and improves stability by lowering the centre of gravity and improving front-rear balance a bit.

Unlike most other parts referenced here, the anti-rotation plate is profile cut aluminum plate. However, for test fitting a prototype 3D printed version is perfectly adequate. 3D printing is simply awesome for prototyping in general. The first image shows the Gen 2 mid drive with the Gen 1 anti-rotation plate and an orange coloured 3D printed prototype of the Gen 2 anti-rotation plate. The two motors are similar enough that the Gen 1 plate would actually work. It interferes slightly with a radius in the enclosure casting but this could be addressed with some filing. By making it longer the screw that will affix it to a T-Cycle idler mount will be accessible outside the radius of the CYC 50T chainring and chain guard required on a trike with a 20" rear wheel.



Accommodating Photon Chainline

The Photon is made to be adaptable to many BB widths and as such it has a relatively large minimum Q-factor. The chain line established by the chain ring is therefore farther from the trike centerline than the stock idler positioning was designed to accommodate. Here are the numbers copied from my design notes:

CHAINLINE:

Photon Gen 2	Rohloff Sprocket	T-Cycle Idler
~50mm with specified spacers	57mm + 6.5mm ICE offset = 63.5mm	46mm measured as is 50mm – 63.5mm target 57mm mean

This indicates that offsetting the idler about 10mm farther from the trike centerline will provide a better chain line. But fitting a spacer to increase the offset immediately uncovered a problem that led to multiple prototypes with incremental improvements (Kaizen!). The interference with the steering rod end is shown in the second image.



No problem. I'll profile cut a modified design for the idler bracket out of aluminum. First a 3D printed prototype:



But this part doesn't have to be tremendously strong. Maybe it can be made with ABS plastic if the bending stresses are addressed with ribbing:



This looks like it will work fine. However, the part ended up going through further iterations to also secure shift cables for a Rohloff IGH. Here is the "final" version. The CYC 1-4 cable can be seen behind the idler mount plate.



The next post will show a mount designed for the Intuition Display.

 

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Mounting the Intuition Display

I like locating the display so it is in the field of view when looking down the road so it is mounted to the main boom. After obtaining a 3D printer the display for the Gen 1 was clamped to this 3D printed extension bracket assembly attached to the ICE computer mount.



The "Intuition" display for the Gen 2 mounts quite differently. I decided to mount it directly to a 3D printed extension that brings it into easy view. I'll have to try it out and see if it needs any ergonomic adjustments.



The 3D printed part is shaped to mount the display without additional parts. It is locked in with the supplied hardware. It is hollow so cables can be hidden inside.



Here is the actual ABS printed part on the trike. Some of the snap in cable clamps from the cable management post are visible in this photo.



Speed Sensor Mount

The Photon Gen 1 install used a plastic part machined on a CNC to mount the speed sensor to the steering arm. The Gen 2 retrofit can use a much easier to make 3D printed part.



This is installed in the same location as this prototype machined part made for the Gen 1 install.




Cable Management at the BB

With the anti-rotation plate securing the motor body to the underside of the BB, the cables that connect to it have to loop over the BB. Why not protect these cables and hold them together by routing them through a 3D printed channel affixed to the anti-rotation plate?




Replacing a UK Style Cable Clamp

The clamps that hold the chain tubes are a standard part in the UK but not in North America. Why not 3D print similar ones out of ABS and make them so a nylock nut is a handy press fit on one side?



The next post will feature some parts designed for cable management.

 

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Wire/Cable Management

About a dozen distinct snap on cable clamps were designed and printed with ABS filament. These secure cables for battery power, Photon speedo, display, throttle and 1-4 cables, L & R brake sense cables and 12V accessory cables. The clamps are located mainly on the cruciform and steering arms. The images below show four of the individual clamps and the clamp on the underside of the 3D printed CYC Intuition display arm serving dual duty as a cable clamp.



Though these are quite bespoke for this trike more universal versions of the cable clamps could be modeled. Other possibilities would be versions for just a particular crank drive (e.g. Photon Gen 2) or a parametric version where the particular cable diameters to be captured and the diameters of the frame tubes could be specified. The latter is probably too ambitious for me!

Here are CAD images of just a few of the clamps.









All the clamps are installed but I'm laid up with a leg problem at the moment. I'll capture some pictures of the installed clamps when I'm more mobile. Then where and how they are used will be clear...