Updated mount for Garmin Varia RTL 510 on Topeak racks

In 2017, I wrote about the mount I had developed for attaching a Garmin Varia rearview radar to the existing mounting bracket on Topeak racks. That mount was designed with the original model, the Varia RTL 500, which is horizontally oriented. In 2018, Garmin updated the product with the Varia RTL 510. The new Varia offers various improvements on the original, such as a brighter light, and a vertical profile that is more functional when mounted on a seatpost.

The problem with the new design is that the vertical orientation of the RTL 510 can cause problems for tire clearance when mounted on the back of a Topeak rack when using my original mount, as shown in the photos below.

 

On this particular bike, it's possible to get the light into the original mount, but it touches the rear tire at the bottom, which is apparent in the side view. The actual tire clearance will depend on the size of the tires and the placement of the rack mount on the frame. On this bike, it touches with no room to spare, but I have the same Topeak rack on a different bike where there is at least 1 cm clearance to spare.

The new Varia requires an update to the design that moves the center of the Garmin mount vertically. The center channel of the Topeak rack poses a design constraint on how far vertically it can move, because that center channel is used for attaching various Topeak packs which slide in from the rear. So the light should not go higher than the center of that channel. It is possible to design a mount that would allow the mount itself to stay below that level, but the light would go above it slightly when installed. The second alternative is to keep the top of the light below that level so that packs could be installed or removed with the light in place. I chose for the second option, even though it does not allow quite as much additional clearance. To accomplish that, I moved the mount 1 cm vertically. In addition, I replaced my original 3-bolt mount with a 2-bolt deisng that only uses the center and top holes on the rack, as I believe 2 bolts are more than sufficient to keep the mount secure on the rack.

The mount installs similarly to the old design, with M3 nuts installed in the recesses, M5 angle-head bolts used to attach the bracket to the rack, and the M3 screws that come with the K-Edge bracket used to attach it to the adapter bracket.

With the new bracket installed, the RTL 510 now clears the tire on the bottom, with sufficient clearance on top to install rack bags with the light installed. It's not a lot of space, though. If I were going for a ride in the mud, I would probably put on my old RTL 500 even though its light is not quite as bright as the newer model.

I have already prototyped another variant of this design that allows the light to be moved an additional 1 cm vertically, but would require the light to be removed when installing or removing a bag.

Links:
Shapeways product page

OpenSCAD file
STL file