The front basket been too forward extended of my compact cargo bike,the front oriented CG causes worse slalom, then I built a short version box, what I can carry reduced

So I intent to revise the frame with the same compact bike while capable of mounting a bigger basket

This is an interesting problem.

I worked professionally in vehicle dynamics and suspension design.

There was a very good university study about 15 years ago, proving that gyroscopic stability from the wheels, and castering/trail, were not necessary for bike stability, IF the center of gravity was forward of the steering axis and high like you have, this caused their vehicle, when rolled with no rider, as it leaned ( began to "fall"), the bike would steer in that direction to self-correct. So usually, the weight distribution that you have would be good.

That is not the case with your bike, which has a much more complex front suspension linkage. I would suggest lowering the front cargo height, but that is impossible, due to the wheels leaning in camber in turns; Picture #4 is the most important one.

First, with a front and rear cargo load that seems unstable, remove the rear load, to see if the rear cargo height is contributing to the instability. Because if it is, you can lower the rear cargo height using panniers, with heavy things in the low panniers.

If rear cargo height is not a factor.... well, you cannot lower the front cargo height between the wheels, as the tires will hit the cargo basket.

You are proposing greatly changing the steering geometry, to move the front cargo load back, however the steering change could have a detrimental effect. I wish I could see more details on the current steering and revised steering. Increased moving mass on the steering can be bad; General Motors discovered this in the early 1970s when they tried to apply the steering geometry of a Mercedes-Benz to a car with much heavier steered mass, and it became unstable, they needed to add a steering damper.

My suggestion would be to invest in one of the cargo bikes with a very large, low cargo area between the handlebars and the front wheel, with pushrod or cable steering to the front wheel. I cannot think of the generic name, but Bullitt is one brand. Due to the wide use, I expect they are quite stable, even when stopped, as the load is low enough to have much less moment arm to tip you over. A dual kickstand (center stand) would be good for parking.

I don't think the rear load has something to do with front end load
Just not to let the front load CG ahead before the front wheels axles
The front basket will sway as the suspension arm up & down to avoid interfering with inner wheel, this need to test

I don't think the rear load is causing instability either, but I cannot rule it out conclusively, and it's really easy and fast to test. There have been examples of instability caused by "coupling". "Speed wobble" on conventional bikes is very related to overall mass distribution and torsional stiffness, among other factors.

Your bike has the advantage of the front rack being attached to the frame, so does not oscillate with the steering. My bike has a front rack attached to the fork, so cargo load is "steered" mass. Some mass, mounted low alongside the fork and steering axis, actually improves stability, adds some inertia which was lacking with 20"/406 wheels. Too much mass, forward of the steering axis, can reduce stability.

I can't find it online now, but Blackburn racks used to provide to bike shops, a poster that advised best cargo mass locations for stability on bikes. However, my bike, and your bike especially, deviate from their test bikes, which were full-size 700c touring bikes.

EDIT: Great CAD models! That took some work. Oooo, the second picture indicates the cargo box being steered with the front wheels; I don't know if you want to do that.

There are no linkages between the front basket & the steering system, instead; there are springs between front upper A arms & the basket, hopping act like anti-roll bar absorb bumping energy and when turn and tilt combination pull the basket to sway(turn)

I can't use the 3D drawing software anymore; which projections I did before, now cut and past together

The front end suspension & steering system had well simulated of my leaning trike, I'll keep the kit in operation as possible

I'll be interested to see it when done, I hope it works out.

You said the cargo load is not connected to the steering linkage; That's good, you don't want to increase steered mass.

The A-arms swing vertically; Putting springs between them and the front cargo load as you've said, will have the effect of transfering some of the cargo load as "sprung mass" (supported by suspension springs), to "unsprung mass" (suspension mass) which increases the inertia of vertical movement of the suspension, and that might not be good to do. (EDIT: I might be wrong, as you may just be supporting the cargo load by different springs than the bike as a whole. Interesting.) Perhaps good, if that keeps the cargo box stationary in lateral tilt (more vertical), while the bike tilts when steering, so you are keeping the cargo load more stationary. If so, interesting, I'd love to hear how that works out.

The two front wheels tilting laterally with the bike frame, is innovative and quite correct, so cornering loads go into wheels radially, just like a normal bike, rather than lateral (side) load as with most trikes, and allows a much narrower front track width while still being stable in turns.

I post some front end details

Lower left pic: That appears to be a different bike, a 4-wheeler, with trailing arm rear suspension. Interesting!

The front suspension, with parallel equal length A-arms (I see the top arms are a bit shorter for kingpin inclination to put the steering axis at tire contact center, so a bit of camber change gain, but we will assume equal length): The instant center for the arms is at infinity, so theoretical infinite length swing arm, so the steering knuckle and wheel moves up and down with no camber change. If the arms are parallel with the ground, this puts the roll center at ground level. This is low, so a normal vehicle would have a lot of outside body lean in cornering due to the long moment arm between the center of gravity and the roll center. HOWEVER, with the bike leaning into turns, this is not a factor! Same for the 4-wheeler on trailing arms, at static (not turning), roll center at ground level, and that would change with the bike turning, but again, with the bike leaning into turns, the roll center height has little effect.

These are very interesting bikes. I'm reading now that your bikes are also termed as "bakfiets" (Dutch for "box bike") , same as the long wheelbase "long john" front cargo bikes (I couldn't remember this term earlier), but with 3 or 4 wheels, yours may be more stable at low speed with heavy loads.

Frame and steer linkage modified

Wow, that's quite an accomplishment! I can't tell for sure, but it looks like the design fails to make the inside wheel turn sharper than the outside wheel. (The inside wheel has to turn a smaller radius; so to avoid having the two front wheels fighting each other, the inside one has to turn sharper.)

Wow, I'd like to correspond with you about various suspension ideas for my next bike cargo trailer. The current one is at Wilson Mines Co., road-bike trailer, with lots of pictures and description, and at the end of the page, some ideas for my next one which will be for much bigger and heavier loads. I don't know if there's an appropriate section for that on this forum, or if it should be by PM. I'm sure others would like to be involved in the conversation. I can only post sketches, not nice CAD drawings like Hodala posts. Not particularly related to bikes, but still to matters of suspension, I made a wooden sidewalk car for our kids 30+ years ago, with McPerson-strut-type suspension, including in the front. It is stable at all speeds. (I run when I push them.) Now it's in use for grandkids. You can see it at Wilson Mines Co., kids' wooden sidewalk car .

All my 3D drawings are all well simulated in mechanism movement; I'm building the basket turning linkage soon

It's like brain waves. I was thinking it before you said it. I can't see if the geometry is correct, though I was trying. Having the inside wheel turn tighter is called Ackermann steering geometry. This is usually accomplished by having the steering arms, when steering centered, point at the center of the rear axle, for 100% Ackermann. Low speed vehicles like golf carts run 100%. Simple vehicles with a solid front axle that pivots entirely, moving the outside tire forward and the inside tire aft, like a low-speed cargo bike, that pivoting axle provides 100% Ackermann, because the axle for both wheels is always pointed toward turn radius center.

Higher speed vehicles with significant weight transfer, the outer tire will be more highly loaded in a turn, and this induces a "slip angle", whereby the tread at the ground is not turned as much angle as the roadwheel itself, so you automatically get some Ackermann; Go 100% ack and you have too much at speed. Tire slip angle varies with load, and tire design; Modern ultra-low-profile high performance tires have much lower slip angles, because the sidewall is so short and rigid.

Trailer: That is indeed a MacPherson strut, I can see the spring. Same design but without the spring being coaxial on the damper or kingpin, and it's a Chapman strut.

Is that an SAE Mini-Baja (tm)?

I withdraw all previous doubts about your project. Clearly you are not an amateur, you got mojo.

Baja SAE is single seat student's design competition project, my works are for leisure market I did for some companies

Ah that's right, it's been a long time. The model of the single-seater above, are those portal axles (in aqua blue)? I did independent portal axles on my design.

No wonder you had no hesitancy to modify your cargo bike, you'd already done more complex things.

The rear suspension just like Trophy truck linkage


The rear end of the basket hanging and swinging left & right

Comparing the front rack capacity of before and after different frames, the rack even need not to sway to avoid interference

Trike+2 spare wheels or 5 x 3 all terrain cargo bike

Interesting.
The extra wheels are to keep it from leaning over too far then?

The spare wheels for long distance rally adventure journey; lean angle is about 30 degree, spare wheels won't touch the ground

I love watching this design evolve - thanks for sharing hodala ! Those spare wheel carriers are wild!

It looks like you lengthened your chainstays in the latest iteration. What was the thinking behind that?

The thing about it is that, if it is just to carry spare wheels, it is a LOT of extra weight. Pounds, not ounces.

To me, it would make more sense to carry a spare tire (foldable type) and MAYBE a couple spare spokes, taped to the bike somewhere.

Otherwise, you add so much weight to the bike that you're traveling at walking pace → may as well just walk.

No? What am I missing?

To avoid peddle feet touched to the rear double wheels arms spindle

As you can see 5 wheels all terrain bike