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Another look at tilting tadpole trike designs

February 25, 2025 — BarryK

I have started a new project, to build a full-suspension leaning tadpole trike, from scratch. Previous post:

I have been looking at leaning-trike designs over the last couple of years, and had intended to implement it in the current trike build. But, decided it is too complicated, and ended up with a non-leaning trike. Here is the tilting mechanism that I considered, late in 2023:

The problem back then, was could not figure out how to connect the tilt mechanism to the steering arms. Have come a long way since then, and now have a design that is simple and looks like it will work. However, taking a bit of a retrospective look, at what others have done and posted on YouTube...

1: Tilting by balance

Most of these are DIY projects. A few guys have built trikes that rely on balance, like you balance on a bicycle. The entire trike, from the rider back to rear wheel, is free to rotate and relies on the rider shifting weight to keep upright. The two front wheels do not rotate, they stay vertical on the ground. In the last couple of blog posts, posted links to "Graham Makes Stuff" YouTube videos; in Part-6, he attempted a leaning mechanism, and went for the balance method. He used a disk brake and caliper, like this:

img1

There is a lever on top that locks the disk, so no tilting. Once underway, the rider releases the lever, then relies on balance, just like a bicycle. However, Graham's experience was that it was very difficult to stop the trike from just falling over.

On a bicycle, the rider is high, making it easy to balance; not so on a recumbent trike. There are a few of these type of designs, including this one, in the "Metal Machine Shop" channel:

https://www.youtube.com/watch?v=NkPyv3-LZmU

...he also experienced balance problems, and has proposed a "MK2" with higher seating. That will help, but is it enough?

2: Tilting hard-linked to the turning arms

What I mean by this, is that the lean is directly linked to how much the rider turns the steering arms. So, turn the steering arms to go left or right in a wide arc, the trike will lean a little bit. Turn to go around a sharp corner, the trike will lean into the corner a lot.

An example of this is the AR3 trike:

https://www.youtube.com/watch?v=t1sUOtY4fYs

img2

Reports from tests are that directly linking leaning to turning radius is not so good. For example, you might turn the steering to negotiate a very sharp turn, at very low speed, and the trike will lean way over into the corner; potentially causing the trike to topple, especially if the back wheel has luggage above it, causing a rather high centre of gravity -- that back wheel can drag the entire trike over.

The AR3 has another problem, that you can see from the photo; despite being tilting, the width has to be wide, as the entire front assembly pivots. This trike actually got to production, but was not a success.

3: Independent turn and tilt control

There have been a few of these type, DIY projects. The one that I am most familiar with, was made by Martin, who lives in Western Australia. That was his "EATSRHPV" trike, about 9 years ago:

"EATSRHPV Tilt mechanism with Steering levers completed"
https://www.youtube.com/watch?v=koADanl4-vo

img3

...He has posted a series of videos showing construction; very complicated, but it does work. The steering arms are swiveled forward and back to turn, or moved left and right to tilt. So, independently controlled.

There are some others posted on YouTube that look like this independent control, though construction details and mechanism close-ups are not shown.

Of these, Number-3 is clearly superior.

I have worked out a design for the proposed new trike, that is the same principle as number-3, with the steering arms independently controlling steering and tilting. It is also a very simple design. The plans have already been drawn up on the computer. I keep looking at the plans, wondering if I have missed anything obvious. But, seems OK; full-suspension with correct camber/toe/Ackermann, as well as tilting. Well, we shall see, have parts on order.

EDIT 2025-02-26:
I forgot to mention, there was a Number-2 type that was manufactured in 2014 and was in production, briefly. It was the "Wild Wave", made by Stein Trikes. Here is a video:

https://www.youtube.com/watch?v=zFv9jWgSOOc

There isn't much information about it, but looking at that video, it seems like Number-2, turning and tilting locked together.

Stein Trikes seems not to have published reasons why they discontinued it. Google's "Generative AI" does give reasons, but they are just guesses.       

Tags: light

Planning a recumbent trike built from scratch

February 21, 2025 — BarryK

I posted a few days ago about this proposed new project:

My current custom trike started out as a standard trike that I modified, with front suspension, solar panel, etc. Great, but having got hands-on experience with that, have learnt so much, and now contemplating a new project incorporating everything learnt.

Why not build the trike entirely from scratch? let the imagination run wild! That might seem very ambitious, but I reckon it is doable with basic handyman tools. There are DIY trike plans on the Internet, and YouTube videos of guys showing how they made their trike, but I want a complete rethink.

In the previous post, I put a link to YouTube video playlist "Graham Makes Stuff", parts 1 to 4. Just about everybody who builds something like this, finds that it doesn't  end, they keep thinking of improvements, and they make many changes. Graham is no exception. The year following building the trike, he made a series of modifications, including adding front suspension. See his later videos:

"DIY Trike build part 5. Riding, testing, things I've changed"
https://www.youtube.com/watch?v=Mm20VcANAkw

"DIY no weld trike part 6. More changes, tweaks and improvements"
https://www.youtube.com/watch?v=OhFYDE0yG8M

While I think of it, Ben, the owner of Trisled, an Australian trike manufacturer, the only Australian trike manufacturer, built this for his dad, a one-off:

https://trisled.com.au/solar-mobility-quad/

img1

...very simple mounting of the solar panel. A curved frame and attached with cable-ties. Something to consider.

Designing a trike from scratch, no legacy constraints; this is such great fun! Here is a proposed side view:

img2

There are various objectives, one of which is to get the centre-of-gravity very low. The seat is low, also angled so that the pedals will be quite high -- even high enough that there could be a floor-plate to prevent the feet from falling onto the ground.

The yellow colour is the frame, which will be 50x50x3 square aluminium. The reason for it extending high at the back is for attaching the solar-panel frame. Solar-panel, motor, they will be optional; Plan to build the initial trike human-powered only, so as to keep it simple.

The back wheel will have two shock absorbers, each side of the wheel, to keep the length of the trike as small as possible. Though, the forks will be a bit longer than shown in the above diagram, to allow for greater upward deflection of the wheel.

The front wheels have been moved back, a lot more than my current trike, to avoid the wheels hitting the feet when doing a sharp turn. I still want the trike to be narrow, at most 730mm, so as to easily go through doors. The narrow width is another reason why want to get the centre-of-gravity very low; though, it is not so urgent due to optional tilting.

The green-filled construction is a round rod, at the right end a swivel to which the steering arms will be attached. Now this is very interesting; the steering arms will allow turning left or right, but also control tilt. The two functions are independent; swivel the steering arms to turn left or right, like any normal recumbent trike, move the steering arms to the side for tilt either way.

There will be a simple mechanism to disable tilt, but if it is enabled, you can go around a corner with as much tilt as you want. This is much better than some other tilting trike designs that have tilt directly linked to the turning.

I'm waiting for an eye operation, in the public system here, as I don't have private health insurance. The public health services here in Australia are very good. There is a date set for the operation, but there is the possibility of being called in earlier. So not going on any trike tour or train adventure for awhile. While here at home for the next couple of months, great opportunity to have fun with this next trike project.

The wheel-knuckle, looking forward to building that. It is arguably the most difficult part of the project, but I have it worked out, and can even see how to build it without any welding. Waiting on some aluminium to arrive.    

Tags: light

Staying with SolveSpace for new trike project

February 17, 2025 — BarryK

Here is the previous blog post:

I opened an issue at github:

"Request: option to do not skew outside face end of extruded tube"
https://github.com/solvespace/solvespace/issues/1527

I had edited my original request, as it was asking for more than one thing. Reduced it down to one, which looks like it isn't going to happen, but as ruevs posted, there is a workaround.

Member phkahler saw my original request, which included being able to assemble individual components, with each component allowing movement in all directions, that is, 6-degrees of freedom. He informed me that is already supported, with an assembly:

https://solvespace.com/ref.pl#Link

SolveSpace really is great. There is a learning curve of course, but really it is easy, in retrospect after having learnt how to do things.

Gotta keep busy doing stuff in my senior years. I have a friend who goes on ocean liner cruises; nah, not for me, would just like to work on projects. What I'm thinking of is contructing a trike from scratch, with all plans published online, and videos.

I've learnt so much, and reckon a complete trike can be built in aluminium with only basic workshop tools. Hand tools, but a drill press also required. A metal bandsaw would be good, for accurate cutting of tube, but could get away with a mitre-box.

A tap-and-die set required. The plan is for the entire trike frame be bolted and pop-riveted, then go to a welding shop afterward and get them to strengthen everything with weld beads here and there.

Starting with the most complicated part to construct, the wheel knuckles. I have figured out a fairly simple way to construct this. Here are the wheel knuckles, firstly left-hand with wheel-axis sticking out to the left:

img1

Here is the right-hand knuckle, with wheel-axis sticking out to the right:

img2

The tube heading toward the observer is for attaching the steering linkage. I chose tube instead of a bar, to make assembly easier. There will just be two holes drilled into the central column, both offset from perpendicular by 10 degrees. A drill-press is required to drill the holes, and the tubes can be held in place by tapping bolts, optionally followed by some welding beads.

The angle bracket is for mounting the disk-brake-caliper.

The central column will have threaded holes tapped at each end, to which ball-joints or heim-joints can screw. Square tube with round hole through centre is available; have that on order.

All quite simple, and the proposal is that each step will be fully documented.

Decided to stay with a 3-wheel design rather than a quad, as in some countries, or States within a country, might have unclear laws whether a quad qualifies as "pedal cycle" that doesn't require registration.

Instead, aiming to achieve a very low centre of gravity for cornering stability. The seat will be much lower than my current trike. Maybe also, aim for simplicity; simple non-electric trike, to which a motor can be added afterward.

I'm reminded of Graham, in his "Graham makes stuff" YouTube channel. He has made a trike with aluminium and some old bicycle parts:

https://www.youtube.com/playlist?list=PLGj2SKPXURTtCF_d9F9Gs4_HbKeDTA-Oj

...no welding.

Some good ideas there, but no suspension. Of course we can pick issues here and there, but it's a pretty good effort. Example of one issue is those front wheel-hubs are not really suitable; what is required is hubs with 15mm or 20mm thru-holes, with sufficient strength so the axle won't bend due to being supported on one side only. Those kind of wheel hubs are found in some mountain bikes.    

Tags: light

Maybe have hit a wall with SolveSpace

February 15, 2025 — BarryK

Earlier posts, creating components in SolveSpace:

I have previously created 3D models in SolveSpace, that have complete freedom of movement in every direction; however, that was with line diagrams. The ball-joint linked to above, also has freedom of movement in every direction, but that was achieved by creating two lines in the "Sketch --> Anywhere in 3D" mode; then tubes and a sphere were wrapped around the lines.

The wall that I have hit is that extruded models cannot be created in 3D free of being locked to one of the XYZ coordinates. In the "Anywhere in 3D" mode, I created a rectangle; but SolveSpace is unable to make this coplanar.

Coplanar means that the area of the rectangle is flat, not twisted, which would follow that opposite sides are parallel. Which is a fundamental requirement before extruding.

The trike model that I am proposing to create, would have many modules, each in separate files, but each of those modules must be free of being locked to any coordinate. The trike frame can roll sideways due to the coil springs compressing, up and down, and lengthways.

Yes, SolveSpace can create models with linkages, but too restricted for my requirements. It was fun while it lasted. I have been avoiding FreeDraw, but tonight might have a look at it.

EDIT 2025-02-16:
Maybe there is a solution, using SolveSpace. I have put in a feature request:

https://github.com/solvespace/solvespace/issues/1527

 

Tags: light

Wheel-knuckle designed in SolveSpace

February 15, 2025 — BarryK

Continuing learning, constructing various trike parts, this time the wheel-knuckle. Earlier posts:

Had a go at modeling the wheel-knuckle, but hit a problem, as extrusions are at 90 degrees to the work-surface; there is no mechanism to specify an arbitrary angle. I need extrusions to be 80 degrees, just off being a right-angle.

I came across explanation how it could be done, that I didn't understand. So I did it the only way that I could understand, by creating little wedges. This is the end result:

img2

Intention is it will be all-aluminium, though the wheel-axle could be steel for extra strength. The image is the right-hand-side knuckle. When assembled, the wheel-axle and steering-linkage-arm will both be horizontal, so that the central knuckle shaft will be 10 degrees off-vertical, leaning both backward and inward.

This is an artistic model; in reality those ledges won't be there. The knuckle is the most difficult part of the trike to construct. In my current trike, the knuckle is made mostly of steel, details provided in links here:

https://bkhome.org/nomad/solar-powered-recumbent-trike.html

Actually, have it pretty well sorted out how the knuckle in the above image can be constructed. The axle will just slide into a hole right through the central post, then welded in place.

Anyway, lots of fun, but have to stop. SolveSpace file here.

Here is another YouTube playlist:

"SolveSpace - 3D Stuff"
https://www.youtube.com/playlist?list=PLluslK6uBf4sUY_SgOZhBTb_5Vs-XMHZ6

Great that there are so many videos.

EDIT 2025-02-15:
A "Skew" checkbox has been added to extrusions, November 26, 2024:

https://github.com/solvespace/solvespace/commit/f4cfb60ab5c8dbacd5aea3c4cd33b7e72422dcfb

This enables an extrusion to be any angle, not just perpendicular.   

Tags: light

Universal ball joint created in SolveSpace

February 14, 2025 — BarryK

I'm learning how to create 3D components in SolveSpace, earlier posts:

...actually, after stdying more tutorials, that extrusion limitation is not a limitation; bevels can be created on the extruded corners.

I spent most of today learning how to create a ball-joint. I want a 3D component to represent a flexible joint; ball-joint or heim-joint. It doesn't have to look exactly like the actual physical joint, just close enough to convey what it is. Movement must be in three dimensions, not flexible only in 2D.

Finally got there, this is what it looks like:

img1

The SolveSpace file is here.

The trickiest thing was to get it to be flexible in three dimensions, not just flex in 2D. The trick was, need to start with menu "New Group -> Sketch in 3D" and create two lines, joined at one end. After that, can use the "lathe" feature to extrude tubes around each of the lines, and a sphere in the middle.

It works! I made the arms approximately matching the 10mm ball-joint that I already own, described in this blog post in March 2024:

img2

Quite a lot of fun constructing these components; putting them together into a complete trike may be a challenge, and will certainly test just how good SolveSpace is.

There are a couple of nice SolveSpace tutorial-series on YouTube:

"SOLVESPACE introduction"
https://www.youtube.com/playlist?list=PLrNBWyhqEoKESBQIh1dyZpdGR-tyUh-3_

"SolveSpace - Beginners"
https://www.youtube.com/playlist?list=PLGAjLwYQPgaBafzQTLA84IkTOptOdIsUX

What's next...       

Tags: light

3D bottom swing-arm for custom recumbent trike

February 13, 2025 — BarryK

I posted about exploring various 3D CAD apps, script-based then came back to SolveSpace:

...designed the top swing-arm for my custom trike.

If you look at my custom trike project, the swing-arms, also known as A-arms or wishbones, are welded steel and ball-joints:

"Solar-powered recumbent trike"
https://bkhome.org/nomad/solar-powered-recumbent-trike.html

I'm planning to put stiffer springs on the front suspension, and reduce the wheels from 20 inch to 16 inch.

But also there is this germ of an idea to create plans so anyone can build a similar trike, from scratch. Plan for it to be mostly aluminium, including the swing-arms.

Working toward that, want to model the entire trike in 3D.

Haven't taken my trike on any journeys yet, just ridden around locally. Have learnt a lot about the handling, which is why want the stiffer springs -- they are on order. Going around corners, I can see that stability would be improved if the trike can lean into the corner, so would like to implement that on the next build. Either that, or make it a quad.

Can't go off touring on the trike anyway, as having an eye operation soon, followed sometime after by a train journey.

This evening designed the bottom swing-arm in SolveSpace:

img1

...notice something a bit odd; there are two brackets to which the shock absorber will bolt, a choice of two positions, but you cannot see right through one of the holes. SolveSpace is having some kind of logic problem there. It doesn't surprise me, the complicated mathematics that SolveSpace has to analyze.

The bottom-arm SolveSpace file is here.

Posting this in the "light" category, as it could be the start of an entirely new traveling-light custom-trike project.       

Tags: light

Basket for trike luggage rack

January 10, 2025 — BarryK

Continuing the custom trike project, here is the previous post:

Have now built a "basket" to go on the luggage-rack. It has to be fairly narrow, due to the panniers either side -- although they are below the luggage-rack, they open and expand upward.

Made it from some 25x25x1.4 mm angle that already had, and some scrap masonite for sides and bottom. First photo:

img1

Pretty simple. The side panels are laminated so have water protection. End and bottom panels are raw masonite, so coated them with Bondcrete to weatherseal. Another photo:

img2

If rain protection is required, could make a fabric cover.

Hmmm, wondering when the trike will be ready for a first short tour. Keep thinking of more things to do. Soon...   

Tags: light