Crius cross, Crius square

See what I've done? For PVC structures the Tee is the expensive part and the most restrictive part. Now I can get rid of it in many circumstances.

Say if you want to pack a lot of pipes close together to form a raft like structure. It's not possible with Tee's because of the minimum distance between two pipes. Now you can pack two pipes side by side close to about two PVC pipe wall thickness.

Say if you build a pet cage out of pure PVC pipes. Now you just need a outer frame with rigid Tee's. The "walls" of the cage can be lined with pipes secured by Crius crosses.

Unlike Tee's, now it is not limited to PVC. You can use EMT or PEX for environmental friendliness. And since they are designed to be incompatible with different diameters, so for us there's always something to clip it secure.

Sometimes one clip is not secure enough for the pipe diameter, especially using the Crius cross. You can use concentric Crius clips - the Crius square.

By varying the arc length, it can be very hard to take off the clip unless slipping it sideways. On the other hand, using two clips side by side make it harder to slip sideways.

And if you apply some glue, it's not possible to take them out in many cases.

Minimal kick/push scooter stand/rack

4T - the scooter stand with a twist.

This is what the 4T scooter stand looks like.  It is made of only 4 tee PVC couplers.  So if you count, the material cost is slightly over $1.

The 1st principle of stands is that you have to make use of your own weight.  There is always a groove between the flat feet rest and the front wheel of every scooter.  This is where the scooter is slightly lifted off the ground by a horizontal bar.  Whether the front wheel is turned sideways does not matter.  It depends on what position of the scooter design feels more stable.

The stand is based on the 45 deg slope design common for bikes.

In the original design the two sides of the stand are parallel.  The handle rest on one of the side bars with a little bit off vertical.  It is still very stable.  The intention is to add some guides at the top end of the pipes to make the handle perfectly vertical with respect to the front-rear axis.  However, it was discovered that a little twist of the side bars will do just that.  And because the base is now wider, the stand is more stable.

You can make it prettier, stronger, but you can't beat using only 4 tee's.  So this is it.  Obviously when you are doing a rack you can modify it to be more space efficient.  But you can put the stands as is very closely side-by-side with the twisted legs crossing each other.

If you just lift the handle the stand goes with you.

Self-balancing bike stand / rack

I was moving the bikes from the garage to store outside with weather "proof" covers.  So the kids can take a ride whenever they like without having adults to bring the bikes out of storage.

I was trying to work out the physics but got stuck on some points.  So I built one base on other practical criteria but not on the absolute stability.  It is based on the common 45 deg inclied design.

Inclined bike rack

The stand for one bike, not the whole rack, is itself stable, rigid, do not waste space and do not waste PVC material.  The problem is that the stand is not making use of the weight of the bike itself.  It doesn't matter much for the whole rack but the inherent instability shows with only one "slice" of it.

I shortened the top rail so the wheel rest tightly on the 45 deg slope, shorter than the diameter of the wheel.  Like this, but the angle is 45 deg.

Wheel locked bike stand

In doing so the centre of the wheel is moved away and down from the rack.  But it turns out that the main instability comes from the centre of the wheel, trying to topple over to the sides.  I was doing the opposite that is desirable, that the centre of the wheel (probably top of the wheel too) should be restricted by the stand as much as possible.

I was worry wrongly about that the front wheel will turn itself horizontally and so the whole bike become unstable.  The front wheel does not have the tendency to turn, and friction make it difficult even if it wants to turn.

Vertical lock bike rack

The other is the vertical design that use the top rail and one of the bottom rail to lock the wheel so the weight of the bike is on top of the stand.  However, the vertical bar is too far from the centre and top of the wheel.  You can see there are "wings" on the side for balancing.

Horizontal support bike rack

There are horizontal designs that seem to use the weight of the bike.  And the centre of the wheel is close to the stand, but not the top of the wheel.  In any case it requires the kids to lift the wheel off the ground and onto the stand.  May be just a little bit of lifting but rolling over a pipe is much easier.

Self-balancing bike stand

My design turns out to be looking like a wheel clamp.  The wheel must be standing on two lower points of the stand (A and B), not touching or barely touching the ground.  Then a vertical bar raising up at an angle close to the centre and top of the wheel.

The stand, only about 5" wide (slightly wider than the length of two 3/4" tee couplings), is able to hold the bike vertical against strong wind without anything else.  So I gave up the idea of a rack, allowing the kids to park anywhere they want, even carrying the stand along with a bike ride.

Point C doesn't do anything, not touching the wheel.  It provide closure and support, otherwise the vertical bars on the two side of the wheel will be floating.

There is no need for exact dimensions, as long as the front wheel don't touch the ground.  You can make the length A-B short enough to make sure of that.  Short A-B doesn't lead to instability.  The bike is very stable in that direction.  You can also raise point B off the ground a bit to ensure that the wheel do not touch the ground.  Or use thicker pipes than 3/4".  You can also raise point A off the ground but the front wheel need to be lifted a bit to get into the stand, rather than roll over point A.

The gap between the bars is slightly thicker than the tires so the bike can get into and out of the stand freely.  As of now, because the spokes near the centre are thicker than the tires, this is where the stand holds the bike in position.  If that is not the case, the stand will hold the bike at the top of the wheel.

The perfect angle of the near vertical bars are just incidental.  You just need to make it close to the centre of the wheel and the top of the wheel.

8 tee's and short pipes may be about $2 total.

You can put the bike on a thin wall.

Reinforced PVC tube and perfect PVC cutting tools

I found out that to reinforce long PVC tubes I can just inert a 1/2" EMT conduit into a 3/4" PVC tube.  The combined price is still less than a 2" by 4" piece of wood with the same length.

But why?

A PVC pipe is quite flexible if you look at a 3/4" piece with a length of over 6'.  You can break it up into sections, adding supports in the middle.  But those fittings are also the weak points.  Sometimes you just need a straight long piece of pipe.  Fittings are more expensive (stronger) than the pipes.  You can go thicker but the price of pipe and fittings increase exponentially.

EMT conduit is much stronger and cheaper.  However, there's no easy and neat and cheap way to fit them together.  So I get best of both world by inserting a EMT into a PVC.  For example, a reinforced 3/4" pipe can support an adult bicycle, while you can just put together such a shelf with only PVC fittings.  Also you can add fancy couplings along the pipe without weakening the reinforced pipe.

The advantage of EMT pipe is that it can be cut easily.  Saws are a pain, especially if you have a hand-held jigsaw.  It dawn on me that there may be EMT pipe cutters that is specialized for the job.  There are.  They are the roller blade types for copper pipes.  I use my copper pipe cutter on EMT pipes and it's good.

It dawned on me that why don't I use the copper pipe cutter on PVC pipes.  Excellent.  The shear types is convenient but it's increasing hard for thicker types.  The edge will never be perfect - always at some angles to the pipe length rather than perpendicular.

Someone uses table saws for PVC, which is a mistake.  Saws will generate heat, which will melt the plastic that is a environment concern.  Pipe cutters have no saw dust to breathe in, and they are the most precise among saws and shears.

PVC pipe gadget techniques — no glue no screw

In building PVC pipe furniture and gadgets, glue or screws are often used.  I doubt it is necessary, and arguably weaken the structures.

If you insert a standard PVC pipe into a standard PVC tee, all the way in with a rubber hammer, it's almost impossible to pull it out, even for the thinnest 1/2" CPVC pipes.  To pull the pipe out, you have to have a clamp securely holding on to the pipe, and then twist the tee with hand or tools.  You have to twist clockwise and anticlockwise until the joint come loose, and then the pipe can be taken out.

So, in your end structure, if you can't twist the pipe against the coupling by hand, and there's no direct force to pull the pipe straight from the coupling, you don't need any glue.  This is easy to design and usually very natural thing to do.  For example, if you have one pipe jointing with two tees at each end, and they are of different orientation, you can't twist the pipe against anything else since the tees are fixed in space in the end structure.

The only way you can twist the pipe is to use a clamp directly on the pipe.  Even so, the force needed is great and don't do much damage since the pipe is still in the same position.

The disadvantage of glue is that it is usually toxic or at least contains some undesirable volatile compounds.  It takes time to apply and dry.  And the coupling cannot be reused.  If you don't use any glue, when you change your mind about the design, you just need to cut the pipe and twist it out with pliers.  All parts are reusable.

Some people drill through the coupling part and use bolt and nuts to prevent the joint from coming apart.  Any drilling will weaken the coupling and the pipe.  The nut and bolt will only be effective when the joint already come loose.  They don't come loose if designed properly.  In my roof top rack, a Christmas tree carrier, I don't even use glue or bolts.

Tips for plans.  To be glueless, the plan has to be precise.  I always use spread sheets to calculate the dimensions.  You need the dimension of your structure modified by the dimensions of the couplings.  For example, the top bar of the T character is about 2.5", the height of the vertical bar is about 11/16".  The extra pipe length to insert into the tee socket is 3/4".

I always use standard tee's and occasionally 90 deg turns.  They are much cheaper than the couplings designed for PVC furniture with more variety.  Arguably the standard ones are better too.  You can use two standard tee's to replace a 4 way coupling on the same plane, or a 3 way coupling in the x,y and z axis.  Even though a standard tee joints everything on one plane only, if your dimensions are reasonably accurate, you can put together a cube quite nicely and squarely.  You just hammer the pieces together with a rubber hammer and the pieces will fall in shape.

Tips for the ugly markings on the pipes.  I don't know why but the cpvc markings can be easily removed with sand paper or steel wool.  But it's almost impossible to remove the markings on white PVC pipes.  Solvents will remove the markings but stain the white pipe with whatever colour the ink is.  Most of my gadgets are by the wall and stationary.  So I just need to turn the markings furthermost from the usual line of sight.  It's almost totally hidden unless you go squarely at the back, which is impossible if the gadget is by the wall.

Tips for reusability and flexible joints.  If the joint depth is 0.75", and you want to joint two tee's back to back together, the best pipe length is twice that at 1.5".  If that part does not need to be structural and you want it to be taken apart with reasonable force, make the pipe length 1 1/4".  If the joint is for the purpose of a "lock", that you may take it apart occasionally, make the pipe length 1", and insert the pipe all the way into the stationary coupling first.  In this case, you can also make a hinge.

Perfect low cost custom pet houses

You know I have been building things to improve my bunny house.  The last time he was living in a concrete block bunker with a big grass yard to himself.  That didn't solve all the problems.

I was going to custom made an acrylic house with all the easy to maintain gadgets.  It would be perfect for indoors and outdoors and while we are on vacation.  It was never done because the more I think, the more it's impractical.

Acrylic is expansive and you have to be precise to glue pieces together.

I have been building small PVC gadgets for a while and it suddenly dawn on me why I don't try to build a pet house from scratch.

I have been building very precise PVC pipe structures using only standard tee's at less than 30 cents a piece.  PVC pipes are virtually free - less than $2 for 10 ft.  With the help of a spread sheet, I can build very complex structures.

For pet house, the first problem is the floor.  You can use pipe grids as the floor but still you need something to cover the gaps.  You can use pipe grids for the walls but the total cost of tee couplings can be high, even at 30 cent a piece.

Wood is still the best choice for the floor.  This bunny house is for indoors so I paid for a premium board, so I can nail ready made side guards on it to prevent spills.  The board has to look smooth for indoors and can be painted if needed.  For outdoors a flat particle board will do.  The wood pieces are of standard dimension so I don't need to do any precise wood work (I can't as I only have a jigsaw).

For the walls I use 24 gauge galvanized steel wire forming a 2" grid.  It turns out to be a great idea and looks neat too.  It's easy to drill small holes into PVC pipes with a plastic bit.  I sand the holes briefly with an oscillator tool.

It turns out that it's easy to tie the wire onto the pipes and tighten them.  If you go around the same holes twice or more around the pipe, it will be securely attached.   Add a Cirus clip on the endpoint and you can secure it further.  After you tighten a length of wire, you can keep the tension by Crius clips as in the last post.  Then you continue to wire and tighten the next part.  You can wire the entire structure without one single wire without breaks.  But for modularity I wire only one side at a time, and use separate wires for vertical and horizontal.

This bunny has been known to attack chicken wires and succeeded.  He had a go on the steel wires but can't do anything to it, yet.  Because the wires are hand tight, he managed to put his head through the grid, but fortunately not his feet at the same time.  So, the cage is secure.

This cage is open top with walls two feet high.  But I decided to put in a door so the kids can do the daily chores too.  What you see in the middle is a toddler-proof door.  I still have to add some legs so the vacuum cleaner hose can get under it.  Also, it will be ideal if I don't need to bend down to feed him or clean the cage.

This is 20" by 3'.  I'll build a 2'x4' for outdoors.  It will be higher than the sprinklers can reach so we can put it in his yard without turning off some of the sprinklers.

You can clip anything on the pipes like sunscreen, rainproof sheets, blankets.  The outdoor one will have a roof structure.  You can see the Crius clips in the picture, near the lower left and right corners.

Crius clips - attaching anything thin or flexible to any pipes securely and economically

This is my new awesome "invention" - Crius clips.

You can secure a thin or thick gauge steel wire to any pipe securely without slipping.  There's no slipping.

You can attach a towel or a plastic sheet on to a length of pipe for shelter or projects.  Not even high winds can detach it.

Say if your pipe is 1/2" PVC, pick the next size PVC pipe, which is 3/4".   Use a pipe cutter to cut out about 1/4" length of pipe.  From this O-ring, cut out about 90 deg, or a corner.  The remaining PVC pipe is a Crius clip.

Place the C opening on the pipe you want to clip on.  Push the clip on with your finger and it will go in easily.  It takes two hands to take it back out.

The clip itself is always PVC pipe.  The pipe to be clipped on to is not limited to any material.  For example, for galvanized steel 1/2" EMT pipes, the best clip is to be made from 1/2" PVC pipes (the OD is slightly larger than the EMT pipes).

If you want to clip thick power supply cable or a thick carpet, use two size larger PVC pipes.

I'm into PVC and EMT gadgets and found numerous uses for this Crius clip.

Environment issues: The manufacturing and recycling of PVC involve toxic materials.  PVC itself is stable and harmless as used in drinking water.

PVC and CPVC are supposed to replace expansive copper pipes.  There's no going back to copper as I myself witness micro pores that can form on copper pipes.  This is a nightmare as a leak can develop in any length of pipe.  The leaking can continue for a long period undiscovered.  The reason is still unknown.

The newer PEX are superior in many ways.  But I heard that rats like them too?

PVC will be around for a while.  They are also used to replace metal and wood window frames for energy efficiency.  They are not that environmentally friendly but they last a long long time.  They can be recycled too.

I can't find anything to replace PVC furniture.  Metal couplings cost 10 times more, and they are bulky.

PVC produces toxic fumes when burned.  Ironically PVC window frames and very popular.

There are ways to reduce PVC in furniture though.  For pipes that don't need to be tight fit, you can use steel EMT pipes that is about the same price.  You can still use PVC couplings but they won't exactly fit.  You can use loose pipes, for example, for the horizontal support of beds.  Or for vertical grids to keep things in.