velomobile suspension, advice needed. Build thread

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agniusm   10 MW

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velomobile suspension, advice needed. Build thread

Post by agniusm » Sep 26 2015 6:07am

Can someone advise on double whishbone suspension? I am preparing for quadracycle/velomobile build and would like to have simple suspension. What would be the effect on driving, cornering if i just had lower arm instead of the two with all that geometry and weight? Its planned to be 30-50kmh tops vehicle.
I thought it makes less difference having in mind that bike tyre is round.
Last edited by agniusm on Sep 28 2015 1:21pm, edited 1 time in total.

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Re: velomobile suspension, advice needed.

Post by docnjoj » Sep 26 2015 9:29am

I once designed a front suspension using a ski for the transverse spring. It might have worked but I decided to get the Steintrike Mad max. They have typical upper/lower A-arms and angled spring/shock. Works fine for the last 6 years. Not very heavy or complicated, espceially fo a guy with your welding skills. Mccphierson (sp?) strut or DiDion fronts is possible too. Check out Julian Edgar articles about his trike builds in Autospeed column he writes. Tons of ideas. He even did an air suspension.
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Steintrike Mad Max full suspension trike rear Cute 100H going on: Whoops, Cute wheel broke but I fixed it.
Sun USX delta trike EbikeKit small geared front wheel sort of front suspension for wife

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Re: velomobile suspension, advice needed.

Post by John in CR » Sep 26 2015 2:55pm

I wish I could be of help Agniusm. The front suspension is what forces me toward delta instead of tadpole for a recumbent e-rocket, so please share your results good or bad and we all can learn. The only thing I can offer is that with just a single A support, won't the camber of the wheel change too much with compression of the shock?

Could a simple cheap and light alternative be using a pair of small suspension forks up front, one on each wheel, even avoiding single sided wheels?

Good luck with it,

John

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Re: velomobile suspension, advice needed.

Post by Chalo » Sep 26 2015 6:10pm

Remember, without a parallelogram linkage, the distance between wheels changes with suspension action. That dramatically complicates the steering linkage, probably more than the upper A-arm does.

Swing axles can be OK on unsteered wheels, but they don't work well for steered ones.

You could put the front axle stubs on the ends of a beam, and suspend the beam (e.g. on leaf springs). That could be simpler than what you're suggesting, without harming steering geometry.
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Re: velomobile suspension, advice needed.

Post by agniusm » Sep 27 2015 2:26am

John, the way i see it negative camber is beneficial. For example when you turn right, centrifugal force forces the left suspension to compress and the wheel gains negative camber and the right wheel gains positive camber and that should be good while making turn. I think it sort of works like a leaning vehicle in some way. Just thinking of the top of my head without any background :)

Chalo, doesn't distance between wheels does not change even on double a-arm suspention? The way i see it it should be the same with the single lower arm. I thought dual A-arm alows for the wheel always to stay flat on the surface so the wheels have a grip all the time. As i wrote before, bicycle wheels are round so there must be no issue there. You got me thinking about steering linkage now, and i see what you mean about the distance importance, but how would one overcome that?

I remember now, there was kickstarte for Arctrike for single arm suspension, and I asked the man how was the suspension. He said it was all good even at speeds.

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Re: velomobile suspension, advice needed.

Post by Dauntless » Sep 27 2015 3:42am

Chalo wrote: You could put the front axle stubs on the ends of a beam, and suspend the beam (e.g. on leaf springs). That could be simpler than what you're suggesting, without harming steering geometry.
This is why people missed Chalo. They use the traverse steering a lot on cyclekarts, glorified gokarts with suspension. The pic is using Honda 16" wheels has found on the Supercub, various other small motorcycles and mopeds, etc., you collect them on eBay for $20-40 each, or less even, depending on your willingness to rehabilitate them a little. http://www.cyclekartclub.com/phorum/list.php?2

The leaf springs are for a horse drawn buggy, would you believe. Tried and trusted on numerous cyclekarts, which mostly are for offroad/trail use. http://www.iowavalleycarriage.com/conte ... eat-spring


If you want A arms, you can go the ready made route, if you stick to smaller ATV's. For this price you can buy a whole small Chinese ATV NEW and sell off what you don't use. http://fr.aliexpress.com/item/Modified- ... 76804.html
CyclekartTraverse.jpg
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Re: velomobile suspension, advice needed.

Post by agniusm » Sep 28 2015 11:39am

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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Another method:

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Re: velomobile suspension, advice needed.

Post by Chalo » Sep 28 2015 11:58am

That flex parallelogram design is ingenious and elegant. I like it too. Fiberglass should be more than adequate for the job; try to find pieces with parallel fibers that can run the long dimension of the leaf spring.
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Re: velomobile suspension, advice needed.

Post by agniusm » Sep 28 2015 1:11pm

Thanks Chalo, appreciate your opinion. I would buy from full sheet so i can choose which way(length/ width) i need it to be cut.
I am sort of transforming this thread to build thread and would like to post some goodies i got so far. I bought 4 x 28 inch rims (generic, nothing special), will fit them with Schwalbe marathon plus tyres. Also ordered 2 x Novatec 20mm hubs and got these toys today:

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Cheap cable brakes, but they should be plenty:

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From electronics i got this BMS for 10A charging:

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I will be fitting 3 speed sprocket on differential and will use 2kW scooter hub motor with 2 speeds (John in CR knows them) so i have 6 speeds. Not that i will need them but having them is a bonus:)

Hopefully i will finish making my battery design to fit something elegant but about that later.

I have bought couple of screens and 2 x 20mm 170 degree round cameras to use instead of a mirrors and reduce drag.

I will be looking into making discs for wheels to reduce drag.

I will be thinking about some sort of ceramic heater later to be able to drive the vehicle up to late in autumn.

I will be making this vehicle for 2 adults and a child (Soon to be proud dad, my baby girl is coming and today is 40 week deadline :) )

Just some random ideas i would like to incorporate into this build:)

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Re: velomobile suspension, advice needed. Build thread

Post by docnjoj » Sep 29 2015 8:27am

Old skis for the springs?
otherDoc
E-bike stable at our house

Steintrike Mad Max full suspension trike rear Cute 100H going on: Whoops, Cute wheel broke but I fixed it.
Sun USX delta trike EbikeKit small geared front wheel sort of front suspension for wife

Agniusm/A123 AMP 20 36 volts on the Steini has been taken off.
2x16000 Multisport from HK now gone as they died after 2 years
New Luna 10S bottle battery 13.6AH now on mine
Relatively New 10S4Px2 for wife's bike giving 20ah @ 40 volts home made Panasonic from Tumich. BMS's rule.

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Re: velomobile suspension, advice needed. Build thread

Post by agniusm » Sep 29 2015 8:36am

I dont think it will be stiff enough mate

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Re: velomobile suspension, advice needed. Build thread

Post by agniusm » Sep 29 2015 10:44am

More toys came today:

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Can someone suggest how to calculate what thickness/size fiberglass flat bar i need? I dont want to go totally blind here, rather do some primitive calculations first.

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Re: velomobile suspension, advice needed. Build thread

Post by agniusm » Sep 29 2015 1:44pm

So i found the mechanical prooeties for resin reinforced glass fibre sheet called FR-4. I think it is the same stuff that pcb's are made of.
There is interesting line: Flexural strength (A; 0.125 in) - LW - > 440 MPa (64,000 psi) (LW stands for length wise, warp yarn direction)
The strength in 3 point bending setup is (3FL)/(2bd^2) where:
F is the load (force) at the fracture point (N)
L is the length of the support span
b is width
d is thickness

Perhaps i should look into Euler–Bernoulli beam theory, looks more relevant

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Re: velomobile suspension, advice needed. Build thread

Post by Chalo » Sep 29 2015 9:12pm

With FR-4 or G10, you'll waste half the weight and fiber content by running it across the applied load instead of lengthwise. It's a good material, but yours is not an ideal application for it.

The Chevrolet Corvette had fiberglass leaf springs for decades; it might still have them, for all I know. Those might be a good module from which to cut the springs you need.

Image
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Re: velomobile suspension, advice needed. Build thread

Post by agniusm » Sep 29 2015 11:51pm

What do you mean length wise? The way they are normally used in vehicles?
The way I see it if I use it across on sort of wishbone setup, I could adjust stiffness by clamping them further out or in to the center.

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Re: velomobile suspension, advice needed. Build thread

Post by Chalo » Sep 30 2015 12:16am

I mean all the fibers should run from end to end, not from side to side. (Relative to the spring, not the vehicle).

Most leaf sprung vehicles orient the leaf springs from front to back; the Corvette laid them out sideways. But that's irrelevant to what I'm talking about. Fibers that don't run in the direction the spring flexes do not help you, but they add weight and thickness.
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Re: velomobile suspension, advice needed. Build thread

Post by agniusm » Sep 30 2015 12:22am

So the FR-4 stuff has crossed fiber layers and that is what you had in mind? The corvette springs would be hard to find here in EU :)
Any suggestions for off the shelve material then?

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Re: velomobile suspension, advice needed. Build thread

Post by Chalo » Sep 30 2015 12:36am

I was thinking about pultruded flat bar for your application. The fiber is continuous and oriented along the bar.
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Re: velomobile suspension, advice needed. Build thread

Post by agniusm » Sep 30 2015 1:04am

Got you. Now need to find something local.

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Re: velomobile suspension, advice needed. Build thread

Post by agniusm » Oct 21 2015 5:05pm

So i have found a company that makes all kinds of pultruded profiles including flat bar. Now i need somehow to calculate what sort of material i need. No idea how to simulate that. I was thinking about two 50x10mm per end. I am thinking making adjustable clamps so i could pull them in or out and that way adjust stiffness. I culs probably add another leaf if 2 would not suffice.
A question on wording. I need some sort of self adjustable bearings or steering and most use rod end. I need something that is the same, only has round or any other shape holder to bolt strait to drilled leaf spring.

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Re: velomobile suspension, advice needed. Build thread

Post by docnjoj » Oct 22 2015 8:22am

I hate to sound like a broken record, but in Europe used skis are a dime a dozen. Laminate them for strength and stiffness. That suspension on that gorgeous trike you showed looks like the front suspension is around 7-8 mm thickness each leaf. Just about a cross country ski section. Worth a try due to the inexpensiveness of skis in your area. If it doesn't work, not a big investment. I got a set for my homebuilt trike for $25 delivered. Downhill skis are even thicker and progressive. Yeah I used to ski a lot.
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E-bike stable at our house

Steintrike Mad Max full suspension trike rear Cute 100H going on: Whoops, Cute wheel broke but I fixed it.
Sun USX delta trike EbikeKit small geared front wheel sort of front suspension for wife

Agniusm/A123 AMP 20 36 volts on the Steini has been taken off.
2x16000 Multisport from HK now gone as they died after 2 years
New Luna 10S bottle battery 13.6AH now on mine
Relatively New 10S4Px2 for wife's bike giving 20ah @ 40 volts home made Panasonic from Tumich. BMS's rule.

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Re: velomobile suspension, advice needed. Build thread

Post by Bluefang » Oct 22 2015 9:01am

A bit of a wierd one but what about a FTC trike with the lean controlled for the most part by the steering?

Have the lower suspension arms with a flex join on the under side of the frame. With the upper arm do similar with a flex point at the top of the frame. For suspension using the "ski" method, solidly mount the ski(or more then one) above the flex joint by probably about 10cm and mount it the same height on either ends of the suspension arms. This will allow the trike to lean in either direction and still have some suspension. It wont be perfect but from some of the motorbikes i have seen with a similar system using complicated means it should be a hoot. You will probably need to dish the wheels so that the turning point is inside the wheel, also from memory having them with some camber will give better tracking. Then figure out how to mount the steering to push the trike in either direction, maybe also use a steering dampener from a motorbike to control the max lean angle and how fast it moves for when you are doing slow turns etc.
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Re: velomobile suspension, advice needed. Build thread

Post by agniusm » Oct 22 2015 9:59am

Up States you have cheap stuff, nothing like here, add 15-20% and make the nuber in euros. I have looked at skis, i would need two pairs and that will set me back 80-120eur, thats fine, but inside the ski is wood it tends to loose its shape, then there is metal edges and they are different shape front/rear, perhaps thickness is not even as well.

Bluefang, its not a trike, it will be on four wheels. I like leaning vehicle idea, but at the moment I don't have confidence in building it nor time to experiment. I want to build something functional for 2 adults and a baby so I can ditch my car for most of the year.

I have couple of sketches, but its rough, perhaps I need to post them for more visual of what I imagine it will be like. Later...

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Re: velomobile suspension, advice needed. Build thread

Post by Kai » Oct 22 2015 6:17pm

Great build thread. I'm following this.
Could the OP also show links to components he bought, please?
I have an electric velomobile collecting dust away from home because I don't have a garage or other safe place here at the moment :(
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Re: velomobile suspension, advice needed. Build thread

Post by agniusm » Oct 22 2015 6:31pm

For the differential www.samagaga.com
For 2 20mm Novatec front hubs + tubes www.26bikes.com
I got 4 29" rims locally.
Brake calipers, brake discs, 3 speed cassette from aliexpress.com
BMS from www.bestechpower.com
I also got couple rear view cameras and 2 5" lcd's for the mirrors.
I got 7 Nisan leaf modules but I don't know if I will use them.

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