This blog is a repository for all my the bike-related studies over the past 20+ years. The content ranges from modelling and analytical studies, to hacks and bodges made to my bike equipment. It's all been done in an attempt to make myself faster on a bike, to make the most of my mediocre fitness.
Blog posts have been written from 2020 onwards. The dates of the posts reflect when the work was originally done.
It’s almost complete now, with just a few older posts still to write up.
This is another 3D-printed bike part that I've designed recently.
During the spring this yea I had the idea to make a number of aerodynamic improvements to my road bike, in time for the summer time trial season. Sadly (and as usual) I've had less spare time than I wanted. Also, the CAD design work has taken me longer than I had anticipated.
Anyway, this mount for my Garmin Edge 840 computer is the first of several minor aerodynamic improvements that I'll create for my road bike.
What aero improvements are possible?
I have always been intrigued by the claims made several years ago by Wahoo about the aerodynamic efficiency of their Wahoo Elemnt Bolt. Those claims are summarised nicely on DC Rainmaker's site. Wahoo claimed that the Elemnt Bolt had 50% less drag than the leading competitor (i.e. Garmin) with those drag savings equating to a 1.5 Watt saving (although they didn't quote what speed that was for) but apparently that corresponds 12.6 second savings over a 40km time trial. Those savings are fairly small but not negligible. To put that in context, 12.6 seconds is about half the penalty of having a round bottle on the down tube, according to Specialized's wind tunnel testing (see here).
DC Rainmaker also performed some wind tunnel tests of his own though, which showed that the savings for a Bolt are actually much smaller than Wahoo's claims, more like a 1 second saving, instead of 12.6 seconds, when the computers are mounted horizontally. That's very small, a truly marginal gain.
Still, despite this very small saving, it's something I wanted to do. I felt that the integration with my stem and handlebar could be improved too, which I felt could yield some additional drag savings. Therefore, I pressed ahead and designed the mount.
Mount design
What I wanted from the mount was to something that: 1) Had a more aerodynamic profile at the leading edge.
2) Covers the Garmin's side buttons, which disturb the flow and aren't needed during a ride.
3) Was blended into my stem and the circular section of my handlebar.
The design consists of a 'sleeve' into which my Garmin 840 easily slips into, and separately a mount that bolts onto the handlebar. Once the Garmin is inside the sleeve, it can be fitted to the mount so that it's perfectly flush. The front and back of the sleeve are shaped to help keep the sleeve perfectly flush with the mount, in addition to a central Garmin quarter turn mount (also designed and 3D-printed) that ensures it won't fall out. All of this is quite difficult to describe with words, so I have uploaded a video to YouTube (see below) that shows it in action:
The sleeve and the mount have two cut outs at the bottom left and bottom right corners. This allows me to press the start/stop button on the right and the lap button on the left, as shown in the second video below. There's also a small C-shaped cut-out in the left hand side of the sleeve's thin sidewall, that allows the on/off button to be pressed. I felt that these three buttons were the only three that really needed to be pressed during a ride, with the other computer functions being available via the touchscreen.
Apart from hiding the protruding buttons via the sleeve, what makes this mount aerodynamic is the shape of (1) the leading edge of the fairing and also (2) the blending of the mount around the stem and handle bar.
The mount smoothly curves into the stem face plate and into the round profile of handlebar at the centre. A lot of trial and error was required to get a shape that fits closely to double curvature shape of my 3T stem. This is undoubtedly the most fiddly part of creating 3D designs - getting them to fit with existing parts and geometries that I don't have the CAD surfaces for.
For the leading edge of the mount, I chose to use a NACA 0024 aerofoil profile. This is a general purpose aerofoil with a 24% thickness to chord ratio. NACA's double-0 series aerofoil profiles are used for all sorts of things and I judged it to be a good choice for this kind of application.
The Garmin quarter turn mount and the handlebar mount are connected using M3 machine screws and nuts. I used these dome-headed stainless bolts from eBay, which have dome-shaped heads that have a 6 mm diameter and a depth of 1.8mm.
A few more photos
I'm pleased with how it turned out. I've attached a few more photos below.
The design at the moment is customised to the shape of my 3T Apto stem, so it won't fit to many other stems at the moment. However, if you are interested in printing one of these for yourself, for your bike, then leave a comment below. If I get enough interest, I'll create a generic version that will work with most alternative bar and stem set-ups and will upload it to Makerworld.
Updated 31st Jan 2026:
As requested, I have uploaded the STL, STP and CAD model files so they are accessible to anybody that wants to print this. I have uploaded two versions:
Please read the description before printing and using. There will still be a lot of bikes and stems that even the generic version won't fit onto, unless you adapt the CAD geometry yourself, so please be aware of that.
Hola, I've now uploaded the STL and other geometry files onto the Makerworld website. See the links at the end of the updated blog post if you're still interested in printing it yourself.
Hi, the STL files aren't available at the moment. That's mainly because the design is shaped to fit specifically on my 3T Apto stem, as shown in the photo. Therefore, it won't fit most other stems at the moment. When I get some spare time, I can modify the design so that it has a larger stem cut-out that it allow is to fit the majority of other stems. Once I find time to do that re-design work in CAD, I'll upload the STL file and leave a comment in this blog post to provide a link. I'll also add another comment here, which will (I think) means you'll get a notification.
Hi, I've now uploaded the STL and other geometry files onto the Makerworld website. See the links at the end of the updated blog post if you're still interested in printing it yourself.
Sure, if you're happy to adjust the design yourself, that's fine. I made a quick attempt to adjust the design about two weeks ago, to make more space for a generic stem face plate, but it wasn't as quick to do as I anticipated. If you're willing to give it a go yourself though, that's good. Perhaps the best thing would be to upload the .f3d CAD file (I used Fusion 360 to design it) as well as the STL/STP files. I should have time either tomorrow or Saturday to upload it, and I'll post a comment here to let you know.
Out of curiousity, have you considered a clamp like the model in the link below. Then you can reduce the frontal area a bit, saving a few microwatts and making the looks even more slick. https://barflybike.com/products/race-flipper-for-3t-apto-stealth-stem?srsltid=AfmBOorPjwka6Rtgei9HNN1XWwEwfrEw4NUQZHJGMrbLsxqd3YuqMsBR
Thanks for that link, I hadn't seen computer mount that before. That's great, and in fact I did consider a similar mounting concept for my design, because the 3T Apto stem has that small cut-out in the stem face plate that could potentially be used to attach a mount. I decided that with a 3D printed part, though, the strength probably wouldn't be good enough to use a mount that relies on quite a thin connecting pieces that goes through that hole in the face plate. Now I know this Race Flipper is available though, I wonder if I could buys one of those, use just the face plate mounting part, and adapt my design so that it connects to that GoPro style mount. That would be a much nicer design, as you say.
Yes, I've used PETG. I've made a couple prototype versions in PLA, and they seem fine too, but from what I've read, PLA doesn't like UV light so is less suitable for outdoor use. I expect other stronger filament types like Nylon, ABS or ASA would be even better than PETG, but I haven't gotten around to trying to print those yet on my printer. The PETG mount was on my bike for a few rides before winter arrived and it seems fine. I'll put it back on once spring arrives and the time trial season starts again in few months time.
yay! looking forward to getting a copy. My daughter/husband just bought a very nice Bamboo labs 3d printer. (the expensive version) so i can make that in a gold multi-color to match my Pinarello. I have two time trials this summer and this will help.
That would be a nice touch, if you've got gold filament. I've got a Bambu Lab printer too, a P1S. The new larger printer in their range looks very nice.
That generic version looks great. I've sent the link to my daughter to print. The handlebar mounts that stick just above/overlooking the mount, I wonder if you could extend the top to come over the top of those and provide an additional aero wing curvature over the handlebar. It would essentially cover those. What do you think?
I think I know what you mean, but there’s a chance I might have misunderstood. Extending the curved part at the front, so that it blends out more gradually is a bit problematic because the top of the sleeve has to be flat because that part sits on the build plate, printed upside down. Therefore the curvature has to flatten out by the point at which it gets to rear part of the sleeve. I could extend the whole thing forwards though, to allow it more space to blend out more gradually, or perhaps move it upwards instead. There are a few options. Extending the curved clamp part at the back, so that it tapers more gradually is certainly an option, and I want to do that and also to blend into the wing shaped part of my handlebar, if I had time. What I’ve found is that whenever I finish a design I then spot a few things that I could have improved and I would change if I started again. Then it’s a question of whether I have the time and motivation to improve it! In most cases I don’t and I’m onto another project.
I've worked in the aerodynamics department of a large aircraft manufacturer for over 20 years. In my day job, I'm responsible for the prediction, modelling and measurement of the drag and lift of our aircraft. Much of my interest and knowledge of engineering and aerodynamics spills over into my main hobby, which is cycling (Road, MTB, cyclocross and time trialing).
Diseño espectacular!!! Me gustaría saber mas sobre el proceso de diseño y tmb poder imprimirlo
ReplyDeleteHola, I've now uploaded the STL and other geometry files onto the Makerworld website. See the links at the end of the updated blog post if you're still interested in printing it yourself.
DeleteAre your STL files available for download? I would love this on my bike.
ReplyDeleteis your model available for download? I would love this on my Pinarello
ReplyDeleteHi, the STL files aren't available at the moment. That's mainly because the design is shaped to fit specifically on my 3T Apto stem, as shown in the photo. Therefore, it won't fit most other stems at the moment. When I get some spare time, I can modify the design so that it has a larger stem cut-out that it allow is to fit the majority of other stems. Once I find time to do that re-design work in CAD, I'll upload the STL file and leave a comment in this blog post to provide a link. I'll also add another comment here, which will (I think) means you'll get a notification.
DeleteHi, I've now uploaded the STL and other geometry files onto the Makerworld website. See the links at the end of the updated blog post if you're still interested in printing it yourself.
DeleteWould you be willing to share the design? Adjusting the design to a different stem shouldn't be the hardest part. Cheers
ReplyDeleteSure, if you're happy to adjust the design yourself, that's fine. I made a quick attempt to adjust the design about two weeks ago, to make more space for a generic stem face plate, but it wasn't as quick to do as I anticipated. If you're willing to give it a go yourself though, that's good. Perhaps the best thing would be to upload the .f3d CAD file (I used Fusion 360 to design it) as well as the STL/STP files. I should have time either tomorrow or Saturday to upload it, and I'll post a comment here to let you know.
DeleteAwesome, very much appreciated.
DeleteOut of curiousity, have you considered a clamp like the model in the link below. Then you can reduce the frontal area a bit, saving a few microwatts and making the looks even more slick. https://barflybike.com/products/race-flipper-for-3t-apto-stealth-stem?srsltid=AfmBOorPjwka6Rtgei9HNN1XWwEwfrEw4NUQZHJGMrbLsxqd3YuqMsBR
Thanks for that link, I hadn't seen computer mount that before. That's great, and in fact I did consider a similar mounting concept for my design, because the 3T Apto stem has that small cut-out in the stem face plate that could potentially be used to attach a mount. I decided that with a 3D printed part, though, the strength probably wouldn't be good enough to use a mount that relies on quite a thin connecting pieces that goes through that hole in the face plate.
DeleteNow I know this Race Flipper is available though, I wonder if I could buys one of those, use just the face plate mounting part, and adapt my design so that it connects to that GoPro style mount. That would be a much nicer design, as you say.
Hi, I've now uploaded the STL and other geometry files onto the Makerworld website. See the links at the end of the updated blog post.
DeleteThank you very much!
DeleteOne more question: what printing material do you use? Is it PETG?
ReplyDeleteYes, I've used PETG. I've made a couple prototype versions in PLA, and they seem fine too, but from what I've read, PLA doesn't like UV light so is less suitable for outdoor use. I expect other stronger filament types like Nylon, ABS or ASA would be even better than PETG, but I haven't gotten around to trying to print those yet on my printer. The PETG mount was on my bike for a few rides before winter arrived and it seems fine. I'll put it back on once spring arrives and the time trial season starts again in few months time.
Deleteyay! looking forward to getting a copy. My daughter/husband just bought a very nice Bamboo labs 3d printer. (the expensive version) so i can make that in a gold multi-color to match my Pinarello. I have two time trials this summer and this will help.
ReplyDeleteThat would be a nice touch, if you've got gold filament. I've got a Bambu Lab printer too, a P1S. The new larger printer in their range looks very nice.
DeleteHi, I've now uploaded the STL and other geometry files onto the Makerworld website. See the links at the end of the updated blog post.
DeleteThat generic version looks great. I've sent the link to my daughter to print.
ReplyDeleteThe handlebar mounts that stick just above/overlooking the mount, I wonder if you could extend the top to come over the top of those and provide an additional aero wing curvature over the handlebar. It would essentially cover those. What do you think?
I think I know what you mean, but there’s a chance I might have misunderstood. Extending the curved part at the front, so that it blends out more gradually is a bit problematic because the top of the sleeve has to be flat because that part sits on the build plate, printed upside down. Therefore the curvature has to flatten out by the point at which it gets to rear part of the sleeve. I could extend the whole thing forwards though, to allow it more space to blend out more gradually, or perhaps move it upwards instead. There are a few options. Extending the curved clamp part at the back, so that it tapers more gradually is certainly an option, and I want to do that and also to blend into the wing shaped part of my handlebar, if I had time. What I’ve found is that whenever I finish a design I then spot a few things that I could have improved and I would change if I started again. Then it’s a question of whether I have the time and motivation to improve it! In most cases I don’t and I’m onto another project.
Delete