Wheels from Foam Board and Pipe Insulation

Hello everyone,

This is a short article showing how I make wheels from foam board with rubber-like treads made from foam pipe insulation.

Here is a set of landing gear using these wheels on an 80" flying wing:

The wheels are made from 4 layers of Dollar Tree foam board.  The treads are foam pipe insulation.  The hubs are 3/16" pop rivets drilled out to 9/64" for 1/8" axels.  

I found this neat circle cutter in the Art Department of the local chain craft store (Pat Catan's): 

The orange part has a pivot pin similar to a push pin point.  The black part has a replacable cutting blade similar to a hobby knife.  It has a compartment with 5 extra blades and 3 leads.  It can expand to 12" diameter.  The blades are long enough to cut through both sides of the foam board. I cut at least 75 circles before sharpening the blade.  I was able to touch it up and have made another 20 or 30 cuts and it is still in good condition.

Here is the circle cutter in action:

It cuts neat circles.  

It is best to cut just through the paper on the first side on the first pass then push through the second side on the second pass.  If you have a stubborn spot you can switch it to the other side to finish.

There is some tendancy for the pin to wander through the soft foam material as the cutter works.  It helps to push the knife through the material with your thumb while letting the pivot rest easily in it's hole rather than trying to pivot the whole cutter and let the pivot pin counteract the pressure of the cutter.  It also helps if you can pivot the material instead of the tool.  

Here is a stack of wheel blanks ready for assembly.  Cutting time about 5 minutes:

Assembly starts by taking the number of blanks needed for one wheel and piercing them with a skewer through the center hole left by the cutter.  You can do this as they are stacked.  I have found it easier to go part way through from one side then finish by going all the way through from the other side.  Like this:

After they are all pierced remove all but one.  Make sure that the side away from the point does not have any marks on it.  This will be one side of the finished wheel.  Look through the other three and make sure you have a good side saved for the outside of the last one.  This will be the other finished side. You can use any kind of banged up scrap for the iner layers.  They are just filler. 

Spread glue (squiggly) on the point side of the one that is left on the skewer and quickly add the second blank.  Press it well up against the first while rotating to spread the glue.  Squeeze firmly all around to make sure no thick places are left in the glue.    

Repeat this process with the remaining layers (4 in my case) quickly .  Once the stack is assembled and the glue is still soft, hold it gripping the skewer with your thumbs and fingers while rubing against each side of the wheel.  Then run the asembly against the work table turning it like a wheel barrow wheel.  This will help take any wobble out of the wheel.   This should be done while the glue is still soft on all 4 layers (or yoiu can do it after 2 or 3 layers if it is getting tight) so the assembly must go quickly.  Once you are satisfied with the trueness of the wheel let it rest for a couple of minutes till the glue is set.  Then remove it and repeat the process till all of your wheels are made.

Next it is time to make tires:

I use foam pipe insulation available at your local big box home inprovement store.  The larger sizes are easier to work with .  I think mine is for 1" pipe.  The challenge is getting the tire rings cut evenly.  

I made a cutting jig from foam scraps that works pretty well.  I use a long sharp thin kitchen knife in a sawing motion to do the cutting:

The opening width should be the same as the insulation diameter.  The height should be about 1/2" more than the insulation so you have a place to start the knife.  The distance from the end panel to the slots will be the thickness of the assembled wheel plus about 1/16".  You want the tires to be a little wider than the wheel.  

Here is the cutting jig in use.  Push the insulation up to the stop.  Quueeze lightly to hold it there.  Then cut with a sawing motion and light perssure:

Above my hand in the picture above are 7 "tire" blanks that were cut by this method.. These could be used to make small diameter wheels by cutting foam wheel blanks the right size but we are going to split these and use two to make one larger wheel.

The pipe insulation comes with a slit part way thorugh on one side so it can be split open to slip over the pipe.  We are going to use the same sharp slender kitchen knife to completee the slit and open the rings up:

The next step is to glue the treads on.  Each of the cuts will make a little over 1/2 of the diameter for the size I am making so I glue the first one on and then fit the remaining part.

This is a dry fit showing one tire section fit around the wheel:

The best glue I found is Liquid Nails "Clear Seal" in a squeeze tube.  It has a strong solvent smell but does not attack either foam.  Once dry it holds well.  If you get smears they do not look bad.

The glue is spread in a ribbon around the center two layers of the wheel.   You can see it left on the second half of the wheel in the picture below:

After wrapping the first piece into the glue just go ahead with the second one butting it firmly to the first and overlapping where it is too long:

Then just use the kitchen knife to cut the second off square at the lap.  The piece will be a little long if you cut exactly over the end of the first piece and that is good.  It will compress and help the joints to tighten up:

Push the second piece down into the glue and work the joints till they look continuous;

Put a rubber band around to hold the tread while it dries.

I like to pull a little extra tension on the rubber band at the joints to help "pull" them together.  After the rubber band is on check by squeezing lightly all the way around to center the tread on the wheel.  It should hang over a little on both sides all the way around:

Set that one aside and repeat till you have completed the pile.

After the glue is set (1 hour or so) you can install  the hubs.  I use 3/16 X 3/4" pop rivets that I drill out to 9/64" for 1/8" axels.  The drilling is a little tricky.  It is hard not to go through the sides.   You have to hold the rivet firmly with a small vice grip and let the drill find the center and follow it.  I have had better luck going from the open end than from the flange end but I still lose close to half.  I am going to resharpen a bit with a more tapered point.  I think that will help. 

Once the hub is drilled out you have to enlarge the hole in the wheel to let it pass through.  It is best if both sides of the wheel are a little bigger than the hub but the middle is snug.  I use the point of a cheap plastic mechanical pencil and push it as far as needed, not quite all the way in from either side:

It leaves a nice tapered hole. Do that on both sides: 

Then slip the pop rivet in till it pops through the center.  Withdraw it about half way and put a small wrap of hot glue around it:

Then push the pop rivet into the hole with a twisting motion.  The goal is to have the glue fill the tapered hole on this side.  A little will probably squeeze out around.  It will be still sticky and the easiest way to remove it is to let it stick to your finger.  It will be cool enough that you can roll it up into a small ball and throw it away;

I use a 4-way screw driver handle to depress around the rivet on the second side:

This makes a depression that I then fill with hot glue to secure the pop rivert on the second side.  A little spit on your finger will let you smooth it out before it dries:

The wheels are fit to the axels by the normal FT method.  A hot glue stop is formed at the axel bend. The wheel is put on, flange side out.  The axel is trimmed to length leaving about 3/8".   Then a second stop of hot glue is put on the end of the axel.  I try to make nice neat little balls by going round and round as the glue begins to set.  You can also push out bumps with a wet finger when it is half set.

The end result:

Here is a full set of landing gear for an 80" wing (or any larger model):

A word of caution: These wheels are very functional and pretty durable but the foam will develope flat spots if you store them with the weight of the model resting on the wheels.

Good building and good flying to all!

Please let me know if you have any suggestions or improvements to offer.

UPDATE (8-11-14): Based on question/comment from LordVader I am suggesting that the wheels be sealed with urethane varnish and they could easily be spray painted either silver or to match your plane.  I would suggest doing that before gluing the treads on. I will do a set that way and add some photos an a later update.

Thanks for the suggestion LordVader. 

I have added the urethane article in "Related Articles" below.

UPDATE #2 (8-11-14):  I sprayed the wheel on the right with quick drying metalic silver spray paint before adding the tread.  I used two thin coats on each side and it was dry to touch in about two minutes. I did not do urethane first but that would probably be advisable if you fly in wet conditions. The appearance would be about the same, possibly a little more glossy.  The paint alone will protect from minor moisture exposure. 

Spokes were added with a circle template and Sharpie:

UPDATE (8-12-14): Based on a suggestion from "sconner" I have rounded the edges of this tire to make it look like a "bush tire".  I used the small pie lifter and heated it with a heat gun.  It worked pretty well but requires a light and even touch.  The foam melts pretty easily:

I guess that looks like a bush tire...

Thanks for the suggestion "sconner".