Delta trikes with leaning saddle and front wheel

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John in CR

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There are several examples of leaning delta trikes where the rear wheels don't lean, but the rider and front wheel do lean like a normal bike. The ICE motorize Carver is one, and more recently and electric trike had a video posted in it's thread. For a long time I dismissed these trikes as probably unstable, but now I'm having second thoughts, primarily because implementation could be very simple.

No, it wouldn't enjoy the full handling benefits of a 3 wheel leaner, BUT if the connection to the leaning part of the trike and the motor, batteries, cargo weight between the 2 static wheels have a center of gravity below the axles of the rear wheels it should be extremely stable in turns.

Has anyone ridden one of these kind of trikes? Impressions? Problems I may not be seeing?

If the center of rotation to the leaning front part of the trike is horizontal, then those rear wheels would stay straight like in a car, however, if that center is angled down toward the front the rear wheels would turn too. I can see this as potentially being a real plus and could shorten the turning radius which would be especially helpful in low speed turns. I do worry about the effects and speed, especially in side winds. Anyone have input in this specific area?

John
 
I am not sure, but it sounds like something similar to Flevo bikes?
 
I was thinking something a lot like the Varna trike in the video here http://endless-sphere.com/forums/viewtopic.php?f=3&t=20977 , but with the connection to the rear wheel assembly several inches below the rear wheels' axle, and put the battery weight down there too. The added idea that I'm unsure about is to make that connection to the rear not quite parallel with the ground. Then the rear wheel would turn a bit in the opposite direction of the lean, like the way the python low racer turns.
 
I been thinking about that too...
my guess is that any rear steering would be bad...


the grandaddy of this design is the Honda Gyro,
http://tiltingvehicles.blogspot.com/2009/08/honda-gyro.html
which uses a horizontal pivot.

some other designs here,
http://tiltingvehicles.blogspot.com/search/label/Pedal%20Powered%20-%202%20wheels%20rear

(check out purplepeopledesign, he's a member on ES.)
http://tiltingvehicles.blogspot.com/2009/08/peddle-tilting-trike.html


[youtube]qCrjWPolLcQ[/youtube]
 
A bit more research shows that the Carver vehicle does have a bit of rear wheel steering, so when I go to build one of these things, I'll try to make the connecting tube to the rear wheel pair have an adjustable angle for some different amounts of rear wheel steering. My gut is telling me that some rear wheel steer ala skateboards could be a real advantage, and while it's hard to compare via videos the handling of the Carver vs the Gyro especially with the big difference in wheelbase, I think I can see a benefit to the rear steer in favor of the Carver. Mine would have a longer wheelbase than the Gyro, so rear steer will also help the rear end get around obstacles. That means I can take a better line through the turns instead of the rear wheel just following the front like a trailer. It seems easy enough to give it a try anyway.

The side benefits would be:

1. Make the lean closer to a neutral effect on COG, instead of just falling to down to either side like on a regular bike, which could lead to better balance at very low speeds.

2. Less side loads on the rear non-leaning wheels.
 
Interesting .... I have to ask though, what real difference is there if you lean like a normal bike, and there is a flexible pivot and rear wheels that are staying flat? I'm guessing there must be some sort of dampening or stops to the rear joint? I mean I'm just trying to understand how it works, I get putting a lower COG and having weight on the back 2 wheels so it's freeing up the front half of the bike, but what keeps it from just leaning to the point of letting the front half hit the ground leaving the rear wheels stable?

Again, not a criticism, I'm just not getting exactly how it makes things more stable. :?:
 
LI-ghtcycle,

Stability in the curves is the key advantage of any leaner. Without leaning wheels, all trikes are inherently unstable while turning, so much so that it forced Honda and others to stop making those 3 wheel ATVs. The front half on this trike would be stable in the same way a bike is. An issue with static vertical wheels is the side loads, which bike wheels aren't designed for. ie on a bike unless you get your body out of the bike's centerline, the forces are always in a direct line with the tire, even while turning. The tadpole trikes get around these issues by being very low, too low for me, with a wide distance between the front pair of wheels, and I want a narrow track.

The front half of such a trike like I'm talking about will behave somewhat differently than a regular bike because instead of the lean pivoting at the rear tire's contact patch with the ground, that pivot will be higher. The advantage over a regular trike is that the primary weight of the vehicle, the rider, is always in perfect alignment with the forces during turning. The reason I want to get the COG of the rear unit as low as possible is that the rear wheels can be closer together without making it "tippy" during the side loads of turns.

Preventing the front from flopping over while stopped will be an issue that definitely must be addressed.

Did you check out the video of the Varna I linked to above? I want to take that and try to improve on it.
 
John in CR said:
LI-ghtcycle,

Stability in the curves is the key advantage of any leaner. Without leaning wheels, all trikes are inherently unstable while turning, so much so that it forced Honda and others to stop making those 3 wheel ATVs. The front half on this trike would be stable in the same way a bike is. An issue with static vertical wheels is the side loads, which bike wheels aren't designed for. ie on a bike unless you get your body out of the bike's centerline, the forces are always in a direct line with the tire, even while turning. The tadpole trikes get around these issues by being very low, too low for me, with a wide distance between the front pair of wheels, and I want a narrow track.

The front half of such a trike like I'm talking about will behave somewhat differently than a regular bike because instead of the lean pivoting at the rear tire's contact patch with the ground, that pivot will be higher. The advantage over a regular trike is that the primary weight of the vehicle, the rider, is always in perfect alignment with the forces during turning. The reason I want to get the COG of the rear unit as low as possible is that the rear wheels can be closer together without making it "tippy" during the side loads of turns.

Preventing the front from flopping over while stopped will be an issue that definitely must be addressed.

Did you check out the video of the Varna I linked to above? I want to take that and try to improve on it.
Click to expand...

Yeah, I guess there could be some kind of mechanical/hydraulic locking mechanism that would only let the joint move when underway or some form of resistance to keep things from flopping around.
 
If you also wanted damping for the pivot, so it can smoothly but firmly be moved, rather than pivoting with every little vibration/etc, you can use some of those adjustable/lockable struts from tiltable wheelchairs/powerchairs. Basically they have a button in the end of them that is pressed (via cable from a brake-like release lever) to allow tehm to be adjusted. When it's not pressed, they are very stiff and so the joint pivot wouldnt' flop all over but could still be moved if you wanted it to.

When pressed they'll move relatilvey easily. I think the ones I have here have about 8 or 10 inches of movement in/out. They're very light, only at most 3/4" at their widest, and IIRC about two feet long when extended.

Think of them as lockable shock dampers or struts?
 
In the Drymer (my true love) even though it is a tadpole the lean is controlled by springs and shocks. I believe that the front acts like a solid axle even though it looks like independent suspension. This probably makes the lean progressive with more backforce the more you lean. I would think this could be applied to the rear axle as well in a delta trike. Most leaner trikes have a lockout for stops and traffic lights to maintain verticality when stopped.
otherDoc
 
John in CR said:
A bit more research shows that the Carver vehicle does have a bit of rear wheel steering,
Click to expand...

hi John, u got a source for that?

however, if that center is angled down toward the front the rear wheels would turn too.
Click to expand...

I was thinking about this,
with a pivot axis pointing at the front contact patch,
the rear wheels would not turn unless the pivot axis becomes steeper.

file.php

tilter rear.JPG
 
John in CR said:
Without leaning wheels, all trikes are inherently unstable while turning, so much so that it forced Honda and others to stop making those 3 wheel ATVs.
Click to expand...
One other factor: jumping a 3-wheel ATV and landing on the front wheel is a great way to get maimed or killed if that wheel doesn't stay pointed straight ahead. IIRC some ads for the things even showed them being jumped, even though the consequences of doing it wrong were so harsh...
 
sk8norcal said:
John in CR said:
A bit more research shows that the Carver vehicle does have a bit of rear wheel steering,
Click to expand...

hi John, u got a source for that?

however, if that center is angled down toward the front the rear wheels would turn too.
Click to expand...

I was thinking about this,
with a pivot axis pointing at the front contact patch,
the rear wheels would not turn unless the pivot axis becomes steeper.

Click to expand...

I couldn't find the bit again about the Carver rear turning. It was in a write-up about the development history as part of the son's computer controlled lean steering system.

Excellent point regarding the pivot axis and the front contact patch, so any difference higher or lower will create some rear wheel steer, and if I'm visualizing it correctly we only want the pivot axis at or lower than the contact patch or the rear wheels will turn in the wrong direction...at least that feels like the wrong direction to me unless you're just changing lanes, not turning.
 
davespicer said:
John in CR said:
Without leaning wheels, all trikes are inherently unstable while turning, so much so that it forced Honda and others to stop making those 3 wheel ATVs.
Click to expand...
One other factor: jumping a 3-wheel ATV and landing on the front wheel is a great way to get maimed or killed if that wheel doesn't stay pointed straight ahead. IIRC some ads for the things even showed them being jumped, even though the consequences of doing it wrong were so harsh...
Click to expand...

I only rode one a few times, and they just felt incredibly wrong. I can't imagine jumping one.
 
sk8norcal said:
^ hi, docnjoj, where did find that info? or is it just ur guess?

it is a tadpole the lean is controlled by springs and shocks.
Click to expand...
Click to expand...

Actually a bit of both. If you go to the Drymer website and watch the trike corner you can see (I believe) the connection between the R & L wishbones. It makes sense to use a solid but light axle for the front. Also check out AutoSpeed's Julian Edgar and his new trike build with a solid front axle with DiDion type locaters. Cool stuff and easier to build than my Steintrike independent front suspension. Lighter too.
Here is the thread on E-S to get started.
otherDoc


http://endless-sphere.com/forums/viewtopic.php?f=3&t=19633&start=15&hilit=drymer
 
I just checked the Drymer site and saw that the front upper and lower suspension arms only have a single central pivot in each therefore the most probable explanation is solid arms through the center and parallelogram tilt, not IFS. A true IFS would have to have 2 sets of pivots, one for each side and for each arm (or 2 for A-arms), like my trike and any Formula 1. They also state that they are starting to manufacture this summer, which is just about over. I tried to get info but the site doesn't seem to like English e-mail addresses. It is all in Dutch. I would definitely have to try it first but if i liked it................!
otherDoc
 
A bit of youtubing shows that both BMW and Mercedes have leaning 3 wheel deltas with non-leaning rears, so I think I'm on the right track. I'm guided by simplicity though, along with my lack of any knowledge about front suspensions for 2 wheelers. I couldn't even copy the Drymer's front with confidence, which does look fairly simple.

I also feel that good cargo space is easier to add to a delta, and based on the Eurobike showings 2 wheelers with no cargo or passenger space is the focus. To me those aren't much more than toys for recreation, especially in areas where the infrastructure makes commuting by ebike a dangerous proposition. Ebikes exploded in use in China out of necessity, but in the west, wide spread adoption is more likely to be as an extra vehicle or to replace a second vehicle. They need to carry stuff and a couple of kids or an adult to get out of the primarily for recreation classification.

I'm not saying very bike-like ebikes can't be useful as transportation, just that cargo and passenger room greatly broadens the market. It doesn't help that in a hundred years they haven't figured that out yet for motorcycles unless you count a tiny cargo box and a bit of space on the seat, but that's a pretty weak-ass attempt at more usefulness than just getting one person from point A to B. Electric cars, Volt, Leaf, etc, aren't really all that much better than gas cars. They're just too big and heavy and wasteful in terms of resources, so I have little doubt that EVs will look totally different by the end of this electric revolution. Since our ebikes put us at the cutting edge with the only EVs that make real economic sense, we should lead the way in exploring totally new classes of vehicles.
 
As usual you are right on, John. That leaning 2 seater motorcycle that looks like a jet should be the way things will go, but not for 100G's. Make a true protected 2 seat motorcycle at a reasonable price and lots of folks would use them. Make it electric and you got it made!
otherDoc

edit: I've been looking at Joyces trike with an eye towards making it a front leaner and it looks do-able. It would have to be extended a bit to account for the swivel and I dont know enough about how to make it progressive but I think it could be done. Those trikes sell for as little as $800 new with the handlebars above the seat and I have seen them for as little as $300 used. Might make a good starting point as the wheels are 40 spoke heavy duty and they come with Maxxis high pressure tires.
 
John in CR said:
I couldn't find the bit again about the Carver rear turning. It was in a write-up about the development history as part of the son's computer controlled lean steering system.
Click to expand...

sounds cool,
I been looking for an animation (bare chassis) for some of these tilters. Its hard to tell what's going on from a video..

Excellent point regarding the pivot axis and the front contact patch, so any difference higher or lower will create some rear wheel steer, and if I'm visualizing it correctly we only want the pivot axis at or lower than the contact patch or the rear wheels will turn in the wrong direction...at least that feels like the wrong direction to me unless you're just changing lanes, not turning.
Click to expand...

the gyro's pivot appears to be horizontal..

file.php

100_3168.jpg


bmw clever front...

clever_curving.jpg
 
sk8norcal said:
Excellent point regarding the pivot axis and the front contact patch, so any difference higher or lower will create some rear wheel steer, and if I'm visualizing it correctly we only want the pivot axis at or lower than the contact patch or the rear wheels will turn in the wrong direction...at least that feels like the wrong direction to me unless you're just changing lanes, not turning.
Click to expand...

the gyro's pivot appears to be horizontal..

Click to expand...

It's hard to tell but the angle of the pivot may change with the compression of the suspension. It seems like that care should be taken wrt the lean pivot, and we'd want to keep it near the rear wheels and only a slight steering effect if any, because otherwise it might turn into a real handful and become something like a python low racer. The pythons have some very exacting angle requirements, and this could be even more complex due to an additional steering pivot at the headset.

If handling, especially at speed isn't adversely affected, it would be nice to get some gravity caused stability at vertical to make feet down at stops optional once accustomed to the trike. The problem I see though would be for a strong effect is the seat height being too low for my tastes, or too wide a track at the rear.

Realistically I may have to go to all 3 wheels leaning to get what I want, and I'd be inclined to go with simple like this http://www.fastfwd.nl/index.php?id=36 or the Black Max http://www.fleettrikes.com/blackmax.htm#7mar09. Both of those show enough detail to copy and are pretty simple. What appeals to me about the non-leaning rear approach is all that space that becomes mostly unusable with tires leaning in there. I know some great mountain roads with almost no traffic that would be great for carving up with a full leaner, but realistically I'd only get to go do that rarely, so my focus should be on cargo capacity, not handling better than a gokart.

John
 
Thanks TD. I had actually read through the Jet Trike stuff and found the conclusion a bit vague. He mentions 100mm raise in seat height will cause problems handling on a tadpole, but Rassy has done this and I just raised my seat about 50mm with the other 50 to come from 20" wheel replacing my 16" fronts. You notice the difference in handling but it seems not to affect the trike stability as much as I thought it would. I do have to corner slower , however. No surprise there.
otherDoc
 
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