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Fenders for custom trike

July 25, 2024 — BarryK

Continuing the custom tadpole recumbent trike project, here are recent posts:

The trike came with mudguards (fenders in US English); however, I have to create brackets to mount them in this custom project. Yes, the Wikipedia states that "bicycle fender" is US English, whereas "mudguard" is British English.

As the front now has shock absorber suspension, had to create brackets to hold the fenders:

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The rear of the trike came with a tray mounted on the swing-arm, with fender bolted underneath the tray. However, I want the tray, and panniers mounted beside it, to be on the suspended part of the trike frame, not on the swing-arm. It is a basic principle that as much weight as possible be above the shock absorber, not below. So, have to redesign tray and fender mounting.

The fender is still attached to the swing-arm. I used whatever scrap aluminium strap at hand and found mount points the strap could be bolted to:


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...notice at bottom-left of first photo, there is a small aluminium plate that I riveted to the swing-arm, to attach the bottom-end of the fender.

There is progress, albiet slowly. Waiting on arrival of a short length of aluminium tube, 55mm OD, that will slide into the trike frame and to which the tray can be attached.   

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Foot and leg safety on a recumbent trike

July 10, 2024 — BarryK

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

Back in May 2023 I posted about the dreaded "leg suck":

A diagram, from here:

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...as you can imagine, nasty!

In my earlier blog post, proposed using mountain bike shoes, that have clips underneath. It is possible to walk with these, going click-click on a surface. However, I want to wear ordinary shoes, so ended up buying the Rolls Royce of foot support, the Terra Trike "Heel support pedals with straps":

https://www.terratrike.com/product/heel-support-pedals-w-straps-pair/

US$145. But I bought them from Trisled in Australia; AU$180 plus AU$64.81 freight plus AU$22.26 GST. Total AU$244.81. That's a lot of money, the freight charge seems excessive. Anyway, wanted them. Here they are mounted on the trike:

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Adjusting the boom to suit my leg length, they just clear the front suspension -- but only just.

Note, these safety pedals are very heavy, as they have counter-weight underneath so as to keep the platform upright. Haven't weighed them.

This leads to another safety issue; the length of the crank arms. By "safety" I mean to avoid knee pain. Centre-to-centre they are 170mm, which looks like pretty much the standard for e-bikes. The problem is, I am having knee problems, on and off, and really do want to minimise the amount of bending. Paul explains that 152mm crank arms are better for a recumbent trike:

https://recumbentrambler.com/my-recumbent-tadpole-trike/

I have read about this many times, riders of recumbent trikes reporting a shorter crank is easier on the knees. So, have ordered 152mm crank-pair from Aliexpress.

In case you are wondering what that horizontal bar is for at the front of the trike; two purposes. One purpose is to mount headlights and turning indicators. Second purpose is it  is planned to have two poles going up to support an overhead solar panel.

That latter purpose means that I need to get the boom length sorted out exactly beforehand. So need that shorter crank-pair to fine-tune the boom length.   

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Bash plate for trike

July 09, 2024 — BarryK

Continuing the tadpole recumbent trike customization project, here is the previous blog post:

The front suspension has been re-assembled, hopefully permanently and there can be progress with building the rest of the trike.

Before turning the trike right-side-up, I constructed a "bash plate". Not that I envisage going into rugged terrain that will need underneath bash protection; it is mostly part of mounting for extra storage space. Hence the extra holes:

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...those two stand-offs are welded on. The mild steel bar is 48x2mm section. Another piece of scrap found at the workshop.

There are already two holes on the front-suspension frame. These were intended for the sophisticated steering linkage that I had originally envisaged; but then decided it is too complicated so built a simplified and somewhat compromised steering linkage instead. Thus freeing-up those holes for some other purpose. Here is the bash plate mounted:

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Before turning it right-side-up, will make an aluminium adapter to anchor the backside end of the bash plate to the steering pivot.  

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Wheel knuckle modifications

June 29, 2024 — BarryK

A few days ago, posted photos of the front suspension and steering assembled on the trike:

Have pulled it apart, to fix a few things. Firstly, the wheel knuckles. The history of these goes back to December 2023:

The design has evolved. Here is a later post:

Here is a photo showing the axles on which the wheels will slide:

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To finish-off the axle, the aluminium tube has now been epoxied firmly over the steel. I used cheap "Utility" brand slow-setting epoxy from Bunnings (my usual choice, far cheaper than the alternative brands, sets very hard), smeared it over the steel shaft, slid the aluminium tube over, and inserted a bit more epoxy into the top to fill up:

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The turning radius of the trike was a bit too wide, so I used an angle grinder to cut the sides of the bottom steel cube to allow the ball joint to swing a bit more. Only cut out about 3mm, as the steering arms are also going to limit the turning radius.

Strengthened the bottom steel cube a bit by welding a plate on the back, as shown in the above photo.

Another problem was that the steering-lever extension was not held positively in place. If one of the bolts should loosen, the extension could move slightly. To fix that, welded the extension, also shown in the above photo. Left the bolts in place.

Finally, an etching primer and black coat:

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Tomorrow can start re-assembling.   

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Trike simplified steering linkage assembled

June 24, 2024 — BarryK

A couple of days ago, I posted about a simplified steering linkage that I can put together quickly:

Today manufactured the wheel-knuckle lever extensions. Used 50x3mm cross-section mild steel. Here is a sketch:

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Then assembled on the trike:

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As stated before, there are lots of compromises with this simple linkage.

Fleshing out a bit more how I calculated the amount that the inner wheel was turning a bit too much...

The SolveSpace diagram shows two concentric circles, going through each wheel. The diagram also shows the angle of each wheel, relative to the trike frame. 90 degrees would be the wheels pointing straight ahead. If the diagram is adjusted so that the outer wheel is following the outer radius, we can subtract the two wheel angles to see how much the inner wheel has turned in or out relative to the outer wheel.

There is a formula for calculating the ideal angle for each wheel: A=atan(L/R)

Where L is the length from the front wheels to the hub of the rear wheel. In my case 1200mm. R is the radius of the circle while cornering. A is the angle.

For the example in SolveSpace of inner circle radius 3138mm and outer radius 3583mm, calculating the two required wheel angles:

Aouter=atan(1200/3583)
Ainner=atan(1200/3138)
Aouter=18.52°, Ainner=20.93°
Difference=2.41°

In the SolveSpace diagram, the difference is 3.31°, so the inner wheel has turned 0.9° more than the Ackermann ideal.

EDIT 2024-06-25:
I assembled the arms, so as to evaluate basic steering functionality:

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Have made a list of required modifications, so tonight will completely dis-assemble the trike. Rebuild will probably be about a month from now. Intend for it then to be rideable and will use lock-nuts and thread-lock.      

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Trike simplified steering linkage

June 22, 2024 — BarryK

Continuing the tadpole trike front suspension project, here are recent posts:

...that last link describes a fairly sophisticated steering linkage mechanism, that provides Ackermann compensation and handles the shock-absorber suspension.

However, that linkage is complicated, and for now I just want to get the trike to a rideable state as soon as possible. So, have figured out a linkage design that is very simple and makes use of what is already available.

There are four tie-rods from the trike; the two shorter ones I will use. Also will attach them to the existing mount points on the arms-frame. This diagram shows how it goes together:

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As using the existing tie-rods and arm mount-points, it requires the knuckle-levers to be extended, as shown in red. The red lines are parallel to wheel direction and there is a 15mm offset where the tie-rods are attached.

There are all kinds of compromises.

There is Ackermann compensation, but not perfect. The lower-left curve is a 2m radius, the outer curve is a 2.4m radius. Circles are concentric. If the steering is turned so that the outer wheel is following the 2.4m radius, the inner wheel has turned a bit too much; 1.55° too much.

Turning a larger circle, 3.2m inner radius and 3.6m outer radius, the inner wheel turns 0.9° too much.

Another compromise is that the steering arms swivelling is limited by the seat. This is going to limit turning to about a 2m radius. I guess can live with that.

If a wheel hits a bump, the tie-rod will cause the wheel to turn in or out slightly. I think that the tie-rod can be connected such that the wheel will turn slightly inward with a small bump, and slightly outward with a bigger bump. That situation would be improved with longer tie-rods; however, the other two that I have are too long, and I couldn't figure out how to fit them in, at least not without a huge amount of extra construction.

The only thing required to construct is the knuckle-lever extensions, that I will probably do on Monday.

Pretty much definitely will be wanting to modify this steering design later, but this will get me out onto the road quickly. I'm looking forward to experiencing how much the compromises affect the actual riding handling.

The SolveSpace design is here, with false ".gz".  

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Trike 320 rear fork large gap fixed

June 21, 2024 — BarryK

I posted about this problem:

The rear fork is this part shown in black:

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Thanks to you guys who gave feedback about bending the fork closer. The wheel hub is 135mm, which is a common standard for bicycle rear wheels. However, the fork spacing is 140mm and is too stiff to pull in completely.

At the workshop I attend, received help from Terry, who is a retired school metalwork teacher. We set the fork into a clamp:

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Terry advised to do the bend cold, not to heat the fork, so that's what we did.

At the back, we placed an anvil, on which to rest the other end of the fork. The clamp is used by the woodworking guys. I suppose that an ordinary large g-clamp could be used ...hmmm, maybe not, as some considerable force is required. We lubricated the clamp thread to help.

The thing is to clamp to a certain point, where upon release the fork and it springs back just a couple of millimeters closer than the original 140mm. We were very careful about this, clamping the fork, then releasing, then clamp a bit more, and so on.

Very interesting; it kept springing back to 140mm. But a point is reached where the frame will just start to deform. For us, it was when we clamped the fork to 110mm spacing, then released and it bounced back to 138mm.

138mm, that is perfect. Now, can tighten the skewer knob a little, then flip the quick-release lever and the fork is now properly gripping the wheel hub. This is good news.    

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