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Design of front suspension for leaning recumbent trike

October 18, 2023 — BarryK

I posted yesterday about preliminary design of front suspension for a tadpole recumbent trike:

https://bkhome.org/news/202310/design-of-front-suspension-for-recumbent-tadpole-trike.html

I wasn't going to, but then thought, hey, why not go the whole way, and make it a leaning trike?

In yesterday's post, I did say that the rider can lean into a corner. This is, however, fighting against both the strong shock-absorbers and the momentum that is throwing the rider outward. The result is that the rider might not be able to achieve much of an inward lean of the trike while going round a corner.

However, there are trike designs that allow unrestricted leaning. There are two main mechanisms to achieve this:

  1. The trike is balanced like a bicycle. The downside is that when stationary, the trike will fall to one side, necessitating some kind of lock mechanism (or feet on the ground).
  2. Leaning is linked to the steering mechanism. This tends to be the most complicated, and there is likelihood of hitting bumps getting transferred back to the steering.
As to why a leaning trike is a good thing:
  1. The trike can be narrower, as the leaning will greatly lessen the tendency to roll outward while cornering. This will mean I can achieve the 660mm legal width here in Western Australia.
  2. The wheels will lean just like when cornering on a bicycle, causing greatly reduced stress that is  tending to buckle the outer wheel on a normal trike.

Here is a drawing that shows why leaning into a corner is both good for the wheels and to avoid tipping over:

img1

There have been a lot of leaning trike designs, in many cases some guy tinkering for years in their garage. Some even made it to being manufactured; however, to my knowledge they were all short-lived and there is no manufactured leaning (human-powered) trike currently in production.

Which does lead to the question; is there something wrong with these designs? Too complicated? Too expensive? Not adequately marketed? Handling quirks?

Here are some of the leaning-trike projects that I discovered yesterday:

Rick's trike. Balance like a bicycle, with a lock when stationary. No coil suspension
http://www.recumbents.com/wisil/wianecki/leaning_trike.htm

Panthertrike. This is a delta trike, leaning but no coil suspension
https://sites.uwm.edu/bike-motorcycle-lab/tilting-narrow-track-recumbent-tricycle/
https://panthertrike.com/

AR3. Leaning, but no coil suspension
https://www.facebook.com/p/AR3-Recumbent-Trike-All-Wheels-Tilting-100065134807057/
https://www.youtube.com/watch?v=hyC0chUW7VM
https://www.bentrideronline.com/?p=13051

EATSRHPV. Leaning via steering linkage, with coil suspension
Martin lives in WA!
https://www.bentrideronline.com/messageboard/forum/main-category/specialty-discussions/homebuilders/114331-eatsrhpv-mart-s-full-suspension-tilting-electric-tadpole-trike-build#post1273032
https://www.youtube.com/@martinhill9011/videos
Impressive, but complicated!...
https://www.youtube.com/watch?v=yI6rMFQ05vM

Panthertrike and AR3 were attempts to manufacture. Martin's EATSRHPV and Rick's trike are personal projects in a garage.

Here are some photos and links to lots of leaning trike designs:

https://www.pinterest.com.au/ldhateleyau/tilting-trikes/

This drawing shows that if the place where the two shock-absorber coils meet, is able to move independently of the trike body, then leaning is achieved:

img2

...so, when stationary, that meeting-point can be locked in place to prevent the trike from falling over. Acknowledgement: the above two drawings are taken from here.

It is possible to take the above design one-step further, and use just one shock absorber.

img4

...but then the ability to lock the trike upright when stationary is lost (maybe), and the rider would have to put the feet down on the ground, just like a bicycle. Acknowledgement: photo taken from here.

Applying this single-shock-absorber principle to my design, except have it on the bottom wishbones:

img5

...the main shock absorber has been placed between the two lower wishbones, see "shock absorber" above, and if attached to the existing mount-points, suits a 325mm shock absorber. I do not yet know the optimum length and coil-strength of the shock absorber; will probably just try and see.

As far as stability when stationary; well, might not need any kind of bracing or locking. The reason is, the above design, where the wheels are fixed a certain distance apart, which is the situation when stationary, any roll off vertical requires compression of the shock absorber. This will be another try and see.   

Tags: light

Design of front suspension for recumbent tadpole trike

October 17, 2023 — BarryK

Continuing the custom solar recumbent trike project. The last couple of posts:

The trike has coil suspension for the rear wheel, but no suspension for the front wheels. I want to be able to ride the trike on very rough roads, even heavily corrugated gravel roads like this:

img1

...there are thousands of kilometres of roads like this in inland Australia. Without front suspension, the trike would be destroyed. Well, even if I ride very slowly, it will not be pleasant.

I bought a very cheap go-kart/buggy/ATV front suspension kit:

img2
Will post more details about that, such as how it will be fitted to the trike. For now, some preliminary designing...

This kind of suspension is known as "double-wishbone" or "double A-arm". It is a complicated science to get a vehicle suspension to work satisfactorily. This webpage explains "camber", "castor" and "toe":

https://www.ozzytyres.com.au/news/wheel-alignment-101-lets-talk-camber-caster-toe

I think it is good to have slight negative camber on a tadpole trike (top of wheel will be tilted inward). At least, that is my understanding after a couple of days reading. Trikes have bicycle tyres, with rounded tread, so they handle camber OK. Furthermore, I think that it would be good if the camber becomes more negative when the shock absorber is compressed.

Consider that corrugated road. Both front wheels will hit the corrugation at the same time. The shock-absorbers will compress, the wheels will move up, increasing the negative camber. But, at the same time, the distance between the wheels in contact with the road must remain the same.

If both wheels move up, and the distance between them on the road surface increases, that will greatly increase tyre wear.

I used Solvespace and worked out proportions that satisfy both of these requirements. Here is the Solvespace file, with a false ".gz" appended to the filename (that is, it isn't really compressed):

suspension2e.slvs.gz

Here it is exported to PNG:

img3

...the circle is the central frame of the trike. The 200x200 square is a frame that I plan to manufacture, that will attach to the tube frame. The rectangle is the wishbone-suspension. Immediately to the right is a 90mm line which represents the spindle for the wheel. The 250mm line at 90 degrees to the spindle represents a 20" wheel.

I played with the coordinates and got it to work quite well. That 319.67 distance which is wheel contact on the road, remains within about 2mm over the full range of the suspension. Maybe could tweak it slightly more.

Another design consideration is cornering. The rider will be able to lean into corners, and the wheels will also lean. This greatly aids stability. I have designed it to have overall width of just under 730mm, so as to be able to fit the trike through my front door. Consequently, it is narrower than most trikes, that are over 800mm.

Being narrower, there is more risk of tipping when going round corners. Except, this design allows the rider to lean into the corner. Here is a Solvespace drawing showing leaning to the right:

suspension2e-lean-right2.slvs.gz

img4

And leaning left:

suspension2e-lean-left2.slvs.gz

img5

Look at the first diagram, it shows a distance from centre to wheel of 319.67mm. Multiply by two gives 639.34mm.

Now look at the last two diagrams. 322.83 plus 316.78 gives 639.61mm. Good!

This means that the rider can tilt into a corner, and the wheels will also tilt, while keeping the separation between wheels on the road surface the same.

Looking good. One parameter that I do not know how to handle is caster. It is neutral caster. I will rely on a dampener to reduce any tendency of the wheels to wander from side to side. Not going to ride any faster than 25km/hr anyway.

Toe will be handled using mechanisms already provided with the trike.

I am a suspension novice, so there is going to be an element of surprise in how this turns out. The above design is preliminary, and highly likely to change as get closer to implementation, which is probably a month or two away.    

Tags: light

An easy-to-use pop rivet gun

October 11, 2023 — BarryK

I posted about building an aluminium frame for solar panels:

https://bkhome.org/news/202310/Solar-recumbent-trike-solar-panel-design.html

...and mentioned issues with rivet guns.

I have been discussing pop rivet guns with Rick, via email. Rick has a couple of them, and previous work experience using them.

The two that I own are about 235mm long. I don't have strong "tradie hands" and find that it takes every once of strength in my hand for the final press to break the stem, using 4.0mm pop rivets. 3.2mm (1/8 inch) aluminium rivets are much easier. This is one that I own:

img1

There are two-hands type, with long handles; however, they pose an access problem. I can see how convenient the 90 degree angle of the one-hand type is, for getting into the right positions for riveting the solar panel frame. The one-hand type also leaves the other hand free, which is very useful.

Researching what is available, I discovered a couple of one-hand riveters that have slightly longer handles; approximate total length 350mm. However, I made a discovery, a rivet gun with ratchet mechanism...

It is the Vessel RG-95 rivet gun; amazing, it is made in Japan! Which is getting to be a rarity these days. Furthermore, it is available at a local store, Sydney Tools:

https://sydneytools.com.au/product/vessel-rg95-ratchet-rivet-gun

img2

Yes, expensive, AU$149. Compare that with the Bunnings Craftright gun at only AU$9.98. So, is it worth the extra expense?

Did a test 4.0mm rivet, and it just took 3 or 4 pumps of the handle and it was done. Quite easy on the hands. Then open the handle wide to eject the stem.

Found an online PDF:

https://www.vessel-europe.com/pdf/RG-95_en.pdf

I found a couple of reviews in Japanese -- one person said that "you need a grip strength as much as no different from the normal rivet gun instead of the ratchet type" (that is a google translation) and he/she only gave two stars.

Another person gave four stars and wrote "As a note, the force required for riveting is not changed, so the work is divided by ratchet structure, but it is better not to think that the grip force will be reduced when riveting".

After reading those reviews, I had to test another 4.0mm rivet. My experience is that there is a greater mechanical advantage and it is easier on the hands. In particular, the final step of breaking the stem is easier. One thing that does make it easier is that the handles are close together, which would give the feeling of greater mechanical advantage, compared with handles further apart.

So, is it worth spending that money? For me it is, as I anticipate using this product many times in the future and less stress on the hands makes it worthwhile. On the otherhand, a longer 350mm rivet gun would probably be satisfactory -- nah, I definitely like the handles close together and the repetitive pump action of the RG-95.

Please take this mini-review with a grain of salt. I wouldn't like it if, after reading the above, you went out and bought one, then decided that you don't like it. Try and find some more reviews first. After using it for a few weeks, I intend to post an addendum to this blog post.

EDIT 2023-10-15:
I used the RG-95 ratchet rivet gun for about 3 hours today, adding some reinforcing brackets to the solar panel frame, using 4.0mm aluminium rivets. Very satisfied.

Some Japanese reviewers have stated that the effort required is the same as normal single-hand pop rivet guns. Hmmm, yes, but I am able to apply the rivets with an overall less effort. I think that there is a slight mechanical advantage due to the ratchet mechanism, but also due to the handles being close together, which allows the muscles of the hand to apply more force.

So, if AU$149 is not an issue for you, then I recommend it. If the cost is an issue, then go for one of the cheaper normal rivet guns -- though I do not recommend the Craftright gun.

I had some discussion with Jon (scsijon in the forum) about rivet guns. We found one other single-hand ratchet-type, the Arrow RT189K; cheap, however the reviews on Amazon are good and bad:

https://www.amazon.com.au/ARROW-FASTENER-Ratcheting-Rivet-Tool/dp/B07S5M595B

...Arrow is a USA-based company. A lot of stuff sold on amazon.com.au comes from the USA. The rivet gun is made in China of course. Here is the Arrow company site:

https://arrowfastener.com/tool/rt189k/

There are YouTube videos posted by the Arrow company. I'm not recommending it, just putting the information out there, in case anyone wants to investigate this cheaper alternative.         

Tags: light

Solar recumbent trike solar panel design

October 08, 2023 — BarryK
I am embarking on a solar-powered electric recumbent tadpole trike custom project.

The big problem is, here in Western Australia there is a width limit on unregistered vehicles, or any vehicles, that can be taken on a footpath or cycleway, of 660mm; that's 0.66 metres. Curiously, WA is the only State in Australia that has  a width limit. It is a very old law, probably from the days when footpaths were narrower. Apparently the WA Transport Minister is looking into revising that law.

Almost all recumbent trikes and many mobility vehicles ridden by handicapped and elderly people, are wider than that. Consequently, the police turn a blind eye to that particular law.

So, I am designing the solar panels to be no more than 660mm wide, yet achieve the highest possible wattage, which is a challenge. I am using two 120W "12V" panels. The manufacturer is MPPTSUN/YikSun, product SWF-120W, see details:

https://en.ecosolarpanel.com/ecosovhuen/products/16704051.html

I bought these from China; however, I wanted to find out if these can be purchased in Australia. The only place I could find is Amazon AU site, which looks like a rebrand of the same panel, but maybe it isn't. Dimensions, power, voltage/current, ETFE coating, are the same:

https://www.amazon.com.au/Flexible-Efficiency-Monocrystalline-Degree-Outdoor/dp/B0BBGN2M37

...but look at the price, AU$1,079.88!!! Those probably ship via the USA. A ripoff price.

Note, if you search for 120W flexible panels on Amazon, there will be lots of hits, much cheaper, but inferior in some way. Such as PET coating, not ETFE, and/or lower-efficiency cells. Then there are the outright liers, claiming exaggerated power output -- don't know about Amazon, but there are lots of those false claims on Aliexpress and AU eBay (or used to be, don't know about current situation, as I think the AU consumer watchdog was going to clamp down).

An objective is to build a light frame. Wasn't quite sure how to do it, and be sure that it is rigid, but started putting it together anyway...

It has turned out OK. To save weight, decided to use wire and turnbuckles to achieve rigidity. This photo shows one-half of the frame, upside-down:

img4

The aluminium extrusion is mostly 1.4mm thickness, some purchased from Bunnings, some scrounged from the shed. The tensioning wire is multi-strand 1.5mm diameter stainless steel, also from Bunnings:

https://www.bunnings.com.au/pinnacle-1-5mm-x-50m-stainless-steel-wire-rope_p4310958

...which I discovered is incredibly difficult to cut. Also, unlike galvanised-iron wire, it is very springy, and it was very difficult to tie-off the ends:

img5

And the other end:

img6

...there has to be another way to tie off those ends! Will hunt around on Aliexpress, see if there any kind of crimps or whatever for neatly tieing up the ends. Wonder also, if anything especially for cutting stainless steel wire.

Instead of wire tensioners, I could have made two rigid box shapes, but decided that would be much heavier. Also, want as much unimpeded air flow under the panels.

Note, I will be seeking help from someone to do some aluminium welding soon, and will ask also if some welds can be done here and there on this frame, so don't have to rely entirely on the rivets.

EDIT:
Have ordered these off eBay; a swaging tool and nickel-plated copper swages:

https://www.ebay.com.au/itm/181365084246

https://www.ebay.com.au/itm/174350581501

Also ordered turnbuckles off eBay. Four of them previously purchased from Bunnings are inferior; well, inferior in that they do not have locking nuts included, will have to add them later. Ordered the 4mm ones:

https://www.ebay.com.au/itm/203741287781

Which reminds me of something. I have an old pop rivet gun, that used to belong to my Dad. It is starting to slip when rivetting 3.2mm rivets, so bought a cheap Craftright brand (Bunnings home brand) rivet gun. In my opinion, the mechanism is inferior; the stems do not fall out, have to pull them out. There is also a lack of versatility in how it works, that cannot quite describe from memory. So back to using the old rivet gun.       

Tags: light

Tadpole trike front suspension ideas

September 12, 2023 — BarryK

A "tadpole" recumbent trike has two wheels at the front, a "delta" trike has two wheels at the back. The tadpole trike I have on order, currently en-route from China, is the tadpole variety.

Most trikes that I see in Australia have no suspension, occasionally see one with rear suspension. Mine also is the rear-suspension-only type. I recently read that only about 30% of the impact of hitting bumps comes up via the rear wheel, which does make a good case for wanting front suspension. However, as there are two front wheels, if one wheel hits a bump it won't be transferred directly upward, but via the frame arm -- in other words there will be some twisting of the frame that will absorb the bump.

There is a problem when both front wheels hit a bump, as in the situation of corrugated roads in Outback Australia. Yes, there will likely be some absorption via the frame arms. These roads are killers. I posted a photo a few years ago... yes, this post in mid-2019:

https://bkhome.org/news/201907/corrugated-outback-roads.html

img1

I dream of riding my trike across the centre of Australia, on roads like this. The solar panel and delicate electronics will take a bashing. So why didn't I buy a full-suspension trike, then add solar panels myself? -- because the price will more than double.

The difference in price between trike purchased direct from manufacturer in China and from Europe/USA is staggering -- about 2-3 times. Plus, I was quoted a shipping price from one European manufacturer of about 2,000 Euros -- about AU$4,000.

I should mention; there is an Australia company in Melbourne, Trisled, that manufactures a full-suspension tadpole trike. Yes, made right here in Australia. But the price is about twice that of my Chinese trike. Anyway, I have doubts about their suspension design.

So, if ever do decide to ride across inland Australia, I can convert the front of the trike to have suspension. Ha ha, "fools rush in where angels fear to tread". It does seem doable though. The only tricky bit is might have to do some aluminium welding, for which I will get help.

This is just wild speculation, might never do it. But anyway, have collected photos that show different front-suspension implementations, including some home-built.

Starting with the one that I think is the top-contender, as I can conceive the conversion to be probably the easiest. There was a trike named "Optima Rhino FS", now defunct:

img2

My Chinese manufacturer, Motrike/Trikexplor, did have a full-suspension trike a few years ago, but they discontinued it. They called it their "S320" model:

img3

They still have it listed on their website (yes, I did ask if they would build a one-off just for me, but they politely refused):

https://www.motrike.com/product-item/full-suspension-recumbent-trike/

Here are a couple of home-made designs:

img4

This one is a home-made parallelogram design, that keeps the wheels always vertical to the road:

https://zeept.wordpress.com/2006/05/29/homebuilt-aluminum-trike/

img5

The Arctrike is a failed Kickstarter project:

https://www.kickstarter.com/projects/206205518/the-arctrike-an-all-new-electric-recumbent-trike

img6

Here are some more photos discovered online:

img7

img8

img10

img11

img12

img13

Note, a trike manufacturer, ICE in the UK, has a front-suspension conversion kit, but only for certain ICE models. Azub in Europe also has available the components of their front suspension, and I did consider adapting to my trike; however, was shocked by the prices.

As stated above, don't know if will ever do this, but very interesting to think about!    

Tags: light

Milo Stove: final assembly and first test

August 30, 2023 — BarryK

This is post #6. The previous post in this Milo Stove project:

https://bkhome.org/news/202308/milo-stove-making-some-small-parts.html

I decided to use a barbecue skewer on which the pot will sit:

img1

Here is the variable air intake, viewed from underneath:

img2

Assembled in the Milo tin:

img3

...those holes around the base of the Milo tin were drilled with a step-drill bit. These were recommended by a guy on YouTube, who explained that ordinary drill bits tend to cut jagged holes in thin sheet metal, whereas a step-drill bit drills nice holes. Yes, he is right! I also received an email from Rick advising me how good step-drill bits are.

Ready to go:

img4

Boiled 500ml water in 4 minutes and 30 seconds, very vigorously boiling at 4 minutes and 45 seconds. That is incredibly fast, which is actually not good. Well, not what I want anyway.

Reducing the air intake did not reduce the flame as much as expected; it was still fierce. So, could not achieve simmering.

This has been a lesson, and I am understanding the dynamics better. There is too much heat feedback and the alcohol is boiling too fast; reducing air intake does not reduce the alcohol boiling as expected. The Milo tin is too much of an enclosed environment.

I'm getting a clearer picture of how to improve the design. And, getting more of an appreciation of those guys who spend years developing various alcohol stove designs. Which reminds me; forum member ally sent me a couple of links to these guys who tinker with designs for years:

https://www.youtube.com/@MrHiramCook/videos

https://www.youtube.com/@tetkoba/videos

So, back to the drawing board!    

Tags: light

Milo Stove: making some small parts

August 26, 2023 — BarryK

This is post #5 of the Milo Stove project. Post #4 is here:

https://bkhome.org/news/202308/milo-stove-drilling-the-lid.html

I am using the Speedster burner, but intending to make my own. So have purchased five of these little 30ml aluminium cans (from eBay):

img1

The burner will have to sit right on top of a bolt-head, so I indented the underneath like this:

img2

...used some aluminium tube, then hammered it, to get this indent:

img3

The rotating disk underneath the burner, that will throttle the air-flow, will have a little handle outside of the Milo tin, so as to control the throttling. I am using a small screw and part of a spade terminal. The plastic insulation on spade terminals withstands high temperatures. The screw is small enough so as to be able to forcefully screw into the end of the spade terminal (where wire is normally inserted):

img4

The mesh stand that I previously constructed, on which the pot will sit, will probably not be in the final stove. Instead, there will be a grill of some kind, mounted onto the sides of the Milo tin. I used the ring-pull tops of baked-beans tins to create these mounting brackets:

img5

Used a 25mm chassis hole-punch to cut a very neat hole in the chicken-tin:

img6

Did a preliminary burn test, and the flame was not coming out through the hole, so used pliers to widen the hole. The result is not neat, but the flame came out very nicely, perhaps a bit too much:

img7

The Packafeather stove has a 27mm - 27.5mm diameter hole, so perhaps that is the magic size.

The metal is a bit brittle; could not work it out wider, it tended to break. So might purchase a slightly bigger hole-cutter. Or maybe try a stone grinding wheel to widen the hole a little bit. So, looks like back to Coles tomorrow, to purchase another chicken-spread tin.

As mentioned, will probably not use the wire-mesh pot-stand shown in the above photo. The grid on which the pot sits could be the fan-grill as shown in post #1, or could use stainless steel skewers. Bought these from Coles:

img8

Have other things to do for the next couple of days, but will get back to this project soon.     

Tags: light

Milo Stove: drilling the lid

August 19, 2023 — BarryK

This is post #4 of the Milo Stove project. Post #3 is here:

https://bkhome.org/news/202308/milo-stove-chicken-tin-and-mesh-stand.html

The lid of the Milo tin is being re-purposed as the base on which will sit the alcohol burner. As mentioned in post #3, the air inlet is underneath the chicken-tin. Here are the holes drilled in the lid:

img1

The air-inlet holes are nominally 9mm diameter, though I was a bit cautious and they are actually more like 8mm.

Cutting 8-9mm holes in thin tin is tricky with a hand tool, so I first drilled 2mm, then 5mm, then reamed it out and a final touchup with a round file. My reamer is a hand tool; they are readily available, look like this:

img2

After drilling all the holes, here is what the 30ml Speedster burner looks like when placed on the lid:

img3

The chicken-tin goes over that, held in place by pieces of aluminium rod riveted on three sides:

img4

...have not yet drilled the 25mm hole in the top of the chicken-tin.

The construction plan was created in SolveSpace. Here it is exported to PNG:

img5

As the diagram shows, there will be a circular piece of aluminium underneath the Milo-lid, that can be rotated to adjust air intake.

As you might glean from looking at the diagram, the Milo lid is about 12mm above the bottom of the tin, with 8mm holes right around the bottom-side of the Milo tin. Note also, the Milo tin is being used upside-down.

Of course, this design is an experiment and it will be great if it performs well, but not guaranteed. If anyone thinks that this idea for throttling air intake is patentable, I state right now that the Milo Stove design is public domain. I don't see anything patentable about it; however, patent law in some countries, particularly the USA, is so broken that even the most trivial innovation can be patented.   

Tags: light