I’m in the middle of making a small-scale aesthetic prototype, which I’ll post about later, but in the midst I made this little video showing how the double parallelogram tilting front suspension works. The prototype is made out of black foam core with hockey tape in the joints. Bone simple, very cheap and easy to modify. More on that later.
15 thoughts on “Video: The front suspension explained (sort of)”
It’s just a (very common) double wishbone suspension, except without a sway bar / anti-roll bar.
I have some concerns about using it as a tilting suspension, because the suspension travel is always perpendicular to the ground, which, when the thing is leaned over, may not be the direction you want the suspension to travel in. Also, you end up with your shocks on the low side nearly fully compressed, possibly not having sufficient remaining travel to absorb a bump. The Piagio MP3 seems to solve both of these as best as possible by putting the shocks out on the ends of the suspension arms.
But clearly a number of people have done as you describe, and have great fun with the results.
I think you’re misunderstanding how the shocks interact with the swing arms. The top shock attachment points pivot independently from the swing arms and independent of the body chassis. This means that the shocks do not compress during lean, as you’ve described. If they did, they would resist the lean and not actually allow the vehicle to tilt. You are correct that this is a double-wishbone suspension. The only difference is how and where the tops of the shocks are attached. If you attached shocks in a car this way, it’d tilt too. This particular style of leaning suspension is derived from the Brudeli Leanster prototype, which is photographed extensively in their photo gallery. It’s also used, albeit using different mechanical components, in the Tilting Motor Works conversion kit.
Thank you Nathaniel, I have been designing a leaning 3 wheeler which will actually be an electrically assisted, covered, tricycle. I am working with a similar layout as yours except I’m trying to keep it fairly narrow, which is making me think of shifting the suspension a little during the tilting cycle (I would have to send drawings for clarity). Seeing your model helps me visualize.
Gordon Hoffman of Lewiston, ID
Glad I could help. My initial Streetliner prototype will be bicycle-based, I’m sure.
im no engineer, but is that not the same as the front end on a road grader. the front wheels are able to angle like that as well.
Aerodynamics are a game changer,a few of the enclosed 2 and 3 wheeler’s doubled their range and or mileage just by adding a streamlined body.Years ago GM had the EV-1 electric car in like a beta test with a few consumer’s.Just to show you how important aerodynamics’s play in increasing a vehicles range[or mileage]The EV-1 was and still might be one of the best full size sedans ever built,as far as a low drag number’s.Let’s face it,GM knew the batteries were big and heavy and offered little in the way of capacity,so make it cheat the wind.A few year’s ago BMW built the 3 wheel tilting concepts, the Simple and Clever,the Simple was a aerodynamic fuel sipping beauty,that according to BMW,was as comfortable as their sedans.Sure would like to see it or something similar in production and at a realistic price.I’m so bored of all these heavy rounded squares,with one person on board getting 30 mpg and their no fun to drive at all. .The fastest bicycle in the world,does 82 mph,knowing that 90 percent of all your power goes to overcoming air resistance,it’s clear to see,this bicycle is wrapped in a aerodynamic body,82 mph,that is very very fast!!!Aerodynamics, along with the new batteries which are claiming 4 times the range at half the cost,from 80 miles to 300 plus miles,can you say woweee!!!!Maybe at last will see some fun,efficient vehicles at the showrooms that are fun to drive and maybe they will bring back that American love affair with our vehicles we use to have,I miss that.
Well it’s been a long time since I read or commented on your blog, or whatever you call it now. Glad to see you are still being creative.
Though you had some fun with me at MTTS Chicagoland Raceway, as far as ridiculing me for dumping my MINi/S and buying an ABARTH…I’m loving it and compared to my 2 MINI’s it’s been flawless, mechanically. Now to make it handle like a MINI next year.
Have a great end of year and hope you and yours have a great 2013.
Thanks Robert, glad to hear from you and I’m glad you’re enjoying whatever you’re driving. Happy new year.
Hello, The tilting and spring system can work out fine. I found that making the attachment joints adjustable is critical to get it to function smoothly. This is a video of the one I built. Please comment there.
Thanks for sharing that. What you say about the adjustability makes a lot of sense. The Leanster has a lot of adjustment points on its structure and I figured I’d do the same. I’d be curious to know how your trike behaved when it was OUT of adjustment. What did it do badly?
Hello, What it does badly is dependant on what is not correctly adjusted. Basically, the turning and or tilting is affected. I’m finding that changing the ride height can affect these also. There seems to be a sweet spot that is better than others. I’m working on equations to determine those spots. I’m finding that the last linkage to adjust is always the tie-rods.
Have you built anything beyond your foam prototype?
Here is a question, just how supple is the suspension? Obviously, body roll is not an issue with paralellogram supension however supple, becasue the wheels and body bank into curve, this suggests that either torsion bars or rubber springs with longitudal interlinks, or hydragas would be the best passive option. But, even better, especially on heavier and more powerful scooters, would be hydropneumatic suspension, since it would automatically correct ride height and also be height adjustable. Once again, the suspension of a tilting-wheel vehicle does not need to compensate for roll.
Comfort would depend entirely on the dampening and rebound rates in the shocks, just like on a motorcycle. You’re correct that there aren’t any anti-roll torsion bars in this setup, but even on a car those components don’t effect ride comfort. They only effect body roll, and by extension, grip and the vehicle’s tendency toward under or oversteer. Changing the ride height dynamically on a vehicle like this would be especially problematic because it would adversely effect the steering and leaning geometry. So I’m planning to simply dial in that height and leave it alone, thus relying on the shocks to simply do their job of not only keeping the front wheels on the ground, but in providing a comfortable ride.
Suspension is not simply about comfort, it’s about safety, if my understanding is correct, the impact of hitting a bump in an unsprung vehicle at full speed is similar to the impact of a low speed collision, only vertical rather than horizontal. In actuality, if the think about what anti-roll bars are and how they work, passive anti-roll bars do reduce the amount of vertical movement between opposing wheel pairs. Active anti roll bars stiffen under cornering and so as you say do “effect body roll, and by extension, grip and the vehicle’s tendency toward under or oversteer” without increasing the impact of ground corregations. With any passive suspension system, the ride height decreases with payload, the more supple the supension, the more the height drops per pound of payload. Depending on the height of the wheelbase and the position of the payload, front to rear interlinks can reduce the load related drop, but if you really want a constant ride height, you need self-levelling suspension. And how would changing the ride height “adversely effect the steering and leaning geometry?”
Hello Mr. salzman, congratulations fo the blog and for all that useful information. Also i want to stress how glad i am, and admire you’re passion, for the projects you’re currently working on, in an area you like so much!!
I´ve been wanting to build my own velomobile for quite some time now. Studying the designs of various tadpole recumbent pedal trikes, with barely any knowledge of automotive engineering or industrial design.
The project is still (after 7 years) growing and growing on the drawing board. Never had the tools, or the money, or the time, or the space, never at once.
Its quite a cheaper project than yours but in the same lines…. and my main concern is a making an all terrain, nice to ride, sturdy, cheap and light pedal machine.
I find that applying lean steering solely for my use its impractical, so my question to you would be:
if i wanted both a tilt/lean + normal steering what challenges would i encounter??
I keep hearing ppl going on about digital/hydraulic actuators to control the lean and the repositioning to vertical, also caster and camber problems. The problems i will encounter losing traction on curves if the spring/dampers etc.. as all is theoretical i cant bring my head to understand really where the trick is, what am i missing… cos i find there’s no much big deal if the meassurements are properly done and the cg is under the point of torsion… also they go on looking for ways to lock the bike upwards while normal cornering and releasing when leaning…
so if you could please at some point enlighten me a bit further filling the gaps, i will trully appreciate it.
I know youre quite a busy man, or if you understood half of this ramblings but if you ever had time to answer it would be mostly welcomed
sorry for my limited english, thanx in advance
pd i have some drawings for a tilting trike id like to share and comment w some technical mind… of a push rod suspension, suspended over a center pivotal (like the aprilia magnet, piagio etc) but with double pivotal, top bottom, between the main center boom and the perpendicular boom w the pedals.