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Re: velomobile suspension, advice needed. Build thread

Posted: Nov 01 2015 1:59pm
by agniusm
I had this sketch. Its a very early version, but should give an idea of the apparatus intended:

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I will have road tires. For illustration dug up some from Warehouse

Re: velomobile suspension, advice needed. Build thread

Posted: Nov 02 2015 4:38am
by John in CR
Looks great. If I ever build something like that, it will need another digit on the desired speed so the performance matches the look.

Re: velomobile suspension, advice needed. Build thread

Posted: Nov 02 2015 4:47am
by agniusm
I have not calculated yet the top speed. I want to use that two speed hub motor you discovered shaved for mid drive and a 3 speed cassette on my diff. That will give me a total of 6 speeds. The system will be 48v. Its easy to calculate but I now have lots more things to think about:)

Re: velomobile suspension, advice needed. Build thread

Posted: Nov 13 2015 3:08am
by agniusm
Got the rear hubs anodized to match front ones:

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Re: velomobile suspension, advice needed. Build thread

Posted: Dec 07 2015 6:10am
by agniusm
Got myself a set of tyres, Schwalbe Marathon plus reinforced. Hopefully they will roll good:

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Re: velomobile suspension, advice needed. Build thread

Posted: Dec 07 2015 7:39am
by sigimem
Hey agnuism

great idea I really like the look of your CAD velomobile.
I am stepping in a bit too late I know can't help it.
My advice don´t use 28" wheels (with regular wide hubs) on a velomobile. Without the ability to lean the front wheels will have a very hard time. The driving will probably be more sluggish than with stiffer (smaller) wheels. I experienced this on a tadpole with only 18" front wheels even so it already had 10° negative chamber.

I really like the idea of your front suspension. The Trabant (East German Car) had a similiar (steel spring) front design always liked it for it´s simplicity.
Since your damping is mainly a material and thickness function you might want to test different things or calculate it. Maybe wood/ or skis arent too bad to get an idea of the suspension characteristics needed.

Re: velomobile suspension, advice needed. Build thread

Posted: Dec 07 2015 3:59pm
by agniusm
The idea of the project is efficiency/visual looks. 28 wheels roll better and with such suspension will have more springiness i hope. Its not a racing project, more like recreational vehicle to run around the town. Will see, cant go back now:) I do have some alex dx32 20 inch rims if this setup does not work.

Re: velomobile suspension, advice needed. Build thread

Posted: Dec 07 2015 4:06pm
by Chalo
As long as your hubs are wide enough, lateral stability should be good. The pedicabs I build use hubs 94mm wide, and with strong 700c rims they are reliable under very heavy loads.

Re: velomobile suspension, advice needed. Build thread

Posted: Dec 07 2015 8:14pm
by John in CR
Chalo wrote:As long as your hubs are wide enough, lateral stability should be good. The pedicabs I build use hubs 94mm wide, and with strong 700c rims they are reliable under very heavy loads.
Does that mean the spoke flanges spaced further apart makes for a stronger wheel, especially if they see side loads? I ask because I'm modding a hubmotor with a built on rim to take a spoked rim instead.

Re: velomobile suspension, advice needed. Build thread

Posted: Dec 08 2015 1:06am
by Chalo
John in CR wrote:
Chalo wrote:As long as your hubs are wide enough, lateral stability should be good. The pedicabs I build use hubs 94mm wide, and with strong 700c rims they are reliable under very heavy loads.
Does that mean the spoke flanges spaced further apart makes for a stronger wheel, especially if they see side loads? I ask because I'm modding a hubmotor with a built on rim to take a spoked rim instead.
Yes. Up until the spokes insert to the rim at an angle that makes them kink at the nipple, wider bracing angle is stronger to side loads. That matters somewhat less with two wheelers than it does with three or four wheelers.

Re: velomobile suspension, advice needed. Build thread

Posted: Dec 08 2015 4:38pm
by sigimem
My go on a velomobile would be wide DH front hubs(20mm axle) a 1.4 inch wide 19" aluminium motorcycle rim and 24" Schwalbe Crazy Bob tyres but thats just my 0.02 EUR

Your right you will see maybe your type of ridingdriving 8) fits this rim and tyre combo

Maybe you can design the part that holds your wheel between the to springs (the one that turns around itself) in such a way that it can be flipped around for different tyre sizes or ground clearance?
A sketch would be helpful here tell me if you want one. But basicly your wheel is fixed near to the lower spring by turning the part it is fixed near the upper spring.

If you haven`t already done please read about steering and geometry and keep all levers for the steering short.

Keep up the good work agnuism :mrgreen:

Re: velomobile suspension, advice needed. Build thread

Posted: Dec 08 2015 6:00pm
by macribs
This I need to see completed.

Re: velomobile suspension, advice needed. Build thread

Posted: Dec 08 2015 9:48pm
by chucho
macribs wrote:This I need to see completed.
+1

Re: velomobile suspension, advice needed. Build thread

Posted: Dec 11 2015 11:01pm
by skyeg3
Please keep posting hub and driveline pics! I gotta source parts for my project. Cool looking project.

Re: velomobile suspension, advice needed.

Posted: Dec 12 2015 11:45am
by Triketech
agniusm wrote:Thanks all for replies. The above seems bulky, need something sleak. I came across a trike build with leaf springs that are forming sort of double wishbone suspension. I really like it. It has couple of cm's travel which should take out those small potholes and make a ride little bit smoother. Also i will save at least couple of hundreds on shocks, make system as lite as possible and more aero friendly.
Now as far as materials go, resin reinforced fiberglass should do it without getting into expensive CF? What do ya all think?

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Double transverse leafs can be quite effective given proper design geometry. There are two problems to minimize:

1) Twisting under braking. Forces will encourage caster angle to decrease slightly, not much but enough that under hard braking with the heavy load of a powered velo that you'll notice it lose the "return to center" tracking that caster provides. Putting the upper spring in more of a tension mode by offsetting the mounting point rearward of the kingpin maybe an inch or so, and going the opposite way on the lower leaf will mitigate the twist.

2) Z-Axis (up-down) Virtual Roll Center on turns is a bit tricky to illustrate without graphics. Lateral loads (turning) will induce more bending moment when the mount at the cruciform is below the axle centerline. In effect it will tend to roll the trike the wrong way on turns. An Anti-Roll bar will help.

Front suspension doesn't need to travel far as its basically cushioning your body in line with where your knees are. If you get an inch of motion that's about all you need for pavement. The rear on the other hand is above your head where the cochlear nerves feed the brain with highest motion inputs. So stiff front springs are just fine for avoiding pinch flats and bent rims, and that really about all you'll need.

Fiberglass won't add much weight over CF, and works just as well as a spring. You can also adjust the spring force by adding shorter leafs to the upper leaf.

You can calculate bend loads to determine the rate needed but I wouldn't depend too much on the published figures for Moment of Inertia ("E") for a given material. It will take trial & error. You'll be in the range of 3/8" to 1/2" thick G10 and that will be best cut via waterknife.

I've done some similar designs in Solidworks along with a dual wishbone. You can see some images of them http://www.triketech.com/Trike/recumben ... nsion.html.

Re: velomobile suspension, advice needed. Build thread

Posted: Dec 12 2015 12:38pm
by agniusm
Very informative post, thanks for that.
I am not very concirned about caster and return to zero, though it woul be nice not to have that negative effect.
So what you are saying, twisting both leafs to form trapezoidal shape, and straintening them while inserting kingpin under presure? I mean this / \ instead of this I I?

I was thinking of ordering 5x50 pultruded G10 but then thought it will be too narrow. I will get 10x100. if it will be too stiff, i can always route a channel in the middle to reduce the stiffness. Also i think i will mount these spring with bolts at the center(2) and then have 2 sliding plates at each end. This will leave me an option to stiffen or loosen suspention on the fly.

Re: velomobile suspension, advice needed. Build thread

Posted: Dec 13 2015 10:15am
by Triketech
agniusm wrote:Very informative post, thanks for that.
I am not very concirned about caster and return to zero, though it woul be nice not to have that negative effect.
So what you are saying, twisting both leafs to form trapezoidal shape, and straintening them while inserting kingpin under presure? I mean this / \ instead of this I I?
Rather then trying a form of pre-loading use the geometry to maintain a tension load. Twisting under braking will push the upper kingpin joint forward and pull the lower rearward. Parallel to the frame axis this would mean the cruciform mount for the upper spring would be behind the kingpin center and the lower spring ahead of the kingpin center on the frame axis.

Re: velomobile suspension, advice needed. Build thread

Posted: Dec 14 2015 6:52pm
by bobc
Hi there,
couple of thoughts; 1) caster change would require the springs to bend fore & aft in their "strong" direction (e.g. top one forwards and bottom one backwards), I'd have thought it's unlikely to be much of an issue... I guess we wait & see...
2) steering - toe change in compression - this would be hard to predict. You'll probably have an effective "wishbone length" about 3/4 of the half track. You will need the "track rod" to be split in the middle with the height of the middle bit controlled to try to get zero toe change in bump (compression).
Cheap laser pointers are your friend here - point at a far wall & exercise the suspension to see if you get any toe change. Needless to say, toe errors are a wonderful way of converting your motive force into tyre wear :)

Re: velomobile suspension, advice needed. Build thread

Posted: Dec 28 2015 8:38am
by agniusm
Received my discs, got the wheels build, now to mount rubber and that's that done :)

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Re: velomobile suspension, advice needed.

Posted: Dec 30 2015 3:45am
by ScooterMan101
Triketech,

What about just using just one transverse leaf, with slight downward curve from the center down to the wheels , would that solve the problems ?

Years ago I saw a Microlight we call them trikes here in the U.S. ( one wheel front , two wheels back, motor and prop behind the pilot, hang glider wing ( albeit stronger tubing and dacron sail )
can also be designed/used for powered paragliding,
and it had one fiberglass rear leafspring, in a shallow downward crescent shape, for suspension.



Triketech wrote:
agniusm wrote:Thanks all for replies. The above seems bulky, need something sleak. I came across a trike build with leaf springs that are forming sort of double wishbone suspension. I really like it. It has couple of cm's travel which should take out those small potholes and make a ride little bit smoother. Also i will save at least couple of hundreds on shocks, make system as lite as possible and more aero friendly.
Now as far as materials go, resin reinforced fiberglass should do it without getting into expensive CF? What do ya all think?

Image
Double transverse leafs can be quite effective given proper design geometry. There are two problems to minimize:

Re: velomobile suspension, advice needed. Build thread

Posted: Dec 30 2015 4:01am
by 4sken
Would it not be simple to use Wishbone style suspension and use pistons (Like in self closing doors or the ones on the baggage racks on airplanes) to allow the steering rod to stretch with the suspension? Or if you're willing to dump some cash, A linear motor for steering instead of a mechanism! Yeah you'll lose all road feedback but it would be pretty sweet. Or perhaps you could use something like Bicycle forks on pivots; Straight up-down movement.

Re: velomobile suspension, advice needed. Build thread

Posted: Feb 10 2017 11:06pm
by Mpenn
Still working on this?

Re: velomobile suspension, advice needed. Build thread

Posted: Feb 13 2017 6:31pm
by kevbo
Some years ago I saw a web article about a teacher that had his class making some sort of vehicle...may have been electric, but possibly human power. At any rate, they used the double leaf suspension like you have illustrated, but the leaves were skis. Turns out you can get old skis very cheap at thrift stores...no market for them. You can also get pretty good deals on last years models if you want new ones. You can stack two either full length or partial to increase the rate, and you can use limber XC skis or stiffer downhill ones.

While it is cheap and easy to come by, it is not ideal: Skis come with steel edges and low friction surfaces that add weight but do nothing as a spring.

Re: velomobile suspension, advice needed. Build thread

Posted: Jun 10 2019 2:13pm
by agniusm
Continueing this thread with revised approach. Since this thread started i now have two kids. The goal is to make it spacious for four. I will be using double wishbone suspension I can order ready made. I am imagining I want something that looks like renault ez-pro, shape I mean. Low speed- 30kmh top on four wheels. I imagine it would be 2600mm - 3000mm in length. What would be maximum didn't you can get through bike path gates ? I would like it as wide as I can.
I would like to use solar for topping off, ~700w worth, probably maxeon cells in modules.
I would make tubular chassis with suspention, drivetrain and all electric and pod on top.
Probably use PC clear panels all around.

Re: velomobile suspension, advice needed. Build thread

Posted: Jun 30 2019 2:01pm
by The Toecutter
agniusm wrote:
Jun 10 2019 2:13pm
What would be maximum didn't you can get through bike path gates ? I would like it as wide as I can.
My KMX tadpole trike is 39" wide from front wheel to front wheel. There are some bike paths where I only have about 1-2" of clearance on each side of the bollards.

I'd recommend going no wider than 40" total vehicle width if you're intent on taking this onto the bike paths without any issue.