E-Scooter airless shock absorbing tires

[Cotemar]

E-Scooter airless shock absorbing tires.

A lot of these new E-Scooters have solid tires, so some of the designs are not comfortable to ride on anything but the smoothest pavement.

I was thinking of making some 8 inch wheels like this to see how they would work on the back wheel of my E-Scooter. My E-Scooter has front and rear shocks already, but this type of airless shock absorbing tire may give it an even smoother ride.

 

[torqueboards]

Nice idea. How are you going to make them?

 

[Cotemar]

Nice idea. How are you going to make them?

I made that 3D part in the first picture above. I can export out a DXF file to a laser cutter.

My plan would be to take an 8.5 inch x 1-1/4" inch thick block of rubber and laser cut it from my CAD file. The finish laser cut rubber tire would be 8 inch dia. x 1-1/4" inch thick.

Then I would sleeve the I.D. for two 608 sized bearings with a bore of 8 mm (.31496 inch), an outer diameter of 22 mm (.86614 inch), and a width of 7 mm (.275)

Better Wheel bearings - SKF BEARING, SEALED, 8 ID, 22 OD, Mfr. Part#: 608-2RSH/C3, $5.10 each
http://www.alliedelec.com/search/productdetail.aspx?SKU=R1015300

 

[windtrader]

Definitively on an interesting twist on the current molded hub/tire. Using the hub mesh as the shock has promise. First thing in my mind was the material would need to endure the constantly varying compression placed on the hub from the changing terrain.

Laser is viable as a mainstream production tool. 3D printing might offer more flexibility but finding a material that has the requisite durability is an issue. But for some prototyping it would be an acceptable method.

Another option could accommodate some form of outer tread. Maybe some material with shock absorbing yet durable qualities. Another idea would be to see if the hub could be made to hold a pressurized tire.

Since the hub is twisting under torque, there is a balance between making the mesh thin and absorbent but too flexible and thick and sturdy.

Sounds like a great winter indoors project!

 

[Cotemar]

windtrader,

Your right about the web thickness changing the wheels shock absorbing qualities. My first prototype will be with .125 webbing. If that does not give me the right FEEL then I will laser cut another wheel with thinner webbing. This is only a design project for me as I am not interested in producing them.

 

[rscamp]

If you want a soft ride, you will have to allow significant tread deflection. This will require a suitable design and material with an extremely low loss tangent to avoid very high rolling friction.

 

[ecycler]

Awesome plan and I can't wait to see you move forward with this. I've been watching and waiting for tires like these to become popular for years! haha I would start off with cross drilling circles or at least working the design to generate less acute angles, as it seems to me some of those sharp corners in your rendering are inviting the rubber to shear at the highest stress points. It makes sense to me to start off with something on the stiffer/heavier side and work your way to more open and 'fragile' tires. Also you could encounter some weird harmonic oscillation effects with the suspension at various speeds due. I remember seeing that happen on a wheel design that basically had springs for spokes!

Are you going to be the test pilot?!

 

[Cotemar]

I will be the test pilot. I have access to a laser cutter. The first image will be my 1st proto type. Then, as I use that tire on my e-scooter, I will make iterations off that design if needed.

This is only a project for me to have a bit of fun with.

 

[windtrader]

Great to see progress. It will be fun to see how the prototypes go as surely there will be a few iterations. Not ill meaning but unless you are a PhD in plastic materials as well as dual majoring physics this must be pretty much a guess/.crap shoot on what works as there are so many variables ranging from material selection, dimensions, design of cutouts, etc. Are you planning on bonding a tread around the cut wheel? It seems like the wheel material would offer pretty poor traction.

 

[Cotemar]

This will just be a block of laser cut rubber. If I do not like how it feels. I will take it off and throw it in the trash and put the original wheel back on.

No PhD needed. No tweeking of the zincoyd cravistat. No brain cells lost. Just havin a bit of fun.

 

[sk8norcal]

doesn't the etwow already have these hollow "holes" internally?

ion shows a pic of this in their KS promo video.

I doubt it's unique to them cause i seen the same pic on taobao for other etwow clones.

 

[windtrader]

I believe he is trying to create the flexible rim rather than the tire. From the images you can see there is much more absorbing being done with the flex "spokes".

 

[Cotemar]

doesn't the etwow already have these hollow "holes" internally?

ion shows a pic of this in their KS promo video.

I doubt it's unique to them cause i seen the same pic on taobao for other etwow clones.

Yes, you are correct that the tires do have the internal shock ebsorbers. Like windtrader said. I would like to add to that by using the much larger spoke area for shock absorption.

I really like the carfree airless tires. Just want to see if they can be taken to the next level.

 

[rscamp]

I mentioned this earlier. I know you are just having fun with this but when I see this sort of thing come up I think one very important thing is not adequately considered. It involves the need for a combination of high flexure, adequate damping and low friction losses.

There are several reasons a pneumatic tire works so well with a spring/damper suspension. The tire basically absorbs the surface roughness. It provides little damping to stop bouncing but this is killed by the suspension damper as long as the unsprung mass isn't too high. The spring/damper suspension does the long throw suspending. But, and this is key, the pneumatic tire has very low rolling friction - largely because it itself has so little damping.

Now the wheel itself has to provide "long throw" suspension. Among other things, this means the suspension has to "sit down" and provide quite a bit of flexure just rolling. So the six million dollar question is; how is reasonably low rolling friction achieved in a flexing tire if the material doing the flexing also has to be a velocity damper to avoid the thing bouncing down the road?

 

[Cotemar]

As I play with these airless shock absorbing tires designs. I see two concepts that I will likely make.

The first one will be the Radial Compression tire. This design will locally compress along the outside diameter periphery of the tire as it comes into contact with rocks and debris.

The second design will be a Radial Displacement tire. This design will displace the inside shaft diameter to the outside hub diameter of the tire.

Both designs will most likely have a very different feel. It will be interesting to see which one gives a better ride.

 

[Hummina Shadeeba]

looks like sf down by the embarcadero
looks like youre testing. Id think handling could be strange. awesome though. shock absorbing wheels and airless tires being nitpicky. I had airless tires once, the green ones, took half an hour to get on and the rolling resistance sucked so much I took them off within ten minutes.

 

[windtrader]

Since the wheels you are making are quite small diameter the lateral movement will be easier to control. Just looking at the two designs it seems the compression allows for more lateral control while the spiral may get wobbly.

The material is going to be quite critical. You have to find something that is stiff yet flexible and has sufficient grip as it is both tread and wheel and rim. I guess as long as it has just enough grip to not slip and slide you might sneak by with a hard enough material. Being soft gives good traction but increases all sorts of other stability issues.