Slightly off topic - best PVC type for a DIY project

[Mark Ezrin]

My apologies for an off plumbing question, but this is probably the best place to get my question answered.

I'm building a small cart to transport a heavy kayak. It is 72 lbs without gear and probably pushing 100 lbs after adding gear.

I'm building this out of PVC schedule 40 pipe and fittings. Am I going to see a difference in strength/durability between 1", 1 1/4" or 1 1/2" PVC? Wheels supporting it, FWIW, are 10" pneumatic tires from Harbor Freight and the axle is 5/8" threaded rod. I'll probably add clevis pin retaining clips or a clevis pin to make parts of the kart able to break down.

None of the individual PVC pieces are very long so there won't be a lot of flex with respect to the PVC itself.

Here are some images just to give you an idea of what I'm building. The final design is still in the works as I might configure it to add a 2nd set if the weight is too much.

Thanks so much for humoring me.

 

[WorthFlorida]

A neat little dolly. I do not know your answer but if you find some parts break, you can use electrical PVC Sch 80. It's a little more readily available in th ebig box stores than DWV PVC in Sch 80. Just note that the inside diameter is smaller so that axle setup you have the rod may not fit inside of a Sch 80 pipe.

 

[Sponsor]

 

[wwhitney]

I'm building this out of PVC schedule 40 pipe and fittings. Am I going to see a difference in strength/durability between 1", 1 1/4" or 1 1/2" PVC?

There certainly will be a strength difference in the member; capacity will increase with diameter, particularly flexural capacity. Solid core will have greater capacity than foam core, although 1-1/2" foam core would be stronger than 1" solid core, I would expect.

What I don't know if whether the 1" version will have adequate capacity, or if you'd benefit from upsizing. It's also not clear to me if the surfboard is the controlling load case, or if incidental bumps and loading should control the design.

But PVC is cheap, so if you like the idea of the smaller size and it "feels" OK, you can prototype it with 1". Worse case it fails and you decide to upsize it.

Cheers, Wayne

 

[Reach4]

I find that the schedule 80 gray conduit, while thicker, is not really more rigid that schedule 40 white pressure water pipe. I think they put more plasticizers (softeners) into the conduit.

 

[Mark Ezrin]

A neat little dolly. I do not know your answer but if you find some parts break, you can use electrical PVC Sch 80. It's a little more readily available in th ebig box stores than DWV PVC in Sch 80. Just note that the inside diameter is smaller so that axle setup you have the rod may not fit inside of a Sch 80 pipe.

Thanks for the tip. I appreciate it.

 

[Mark Ezrin]

There certainly will be a strength difference in the member; capacity will increase with diameter, particularly flexural capacity. Solid core will have greater capacity than foam core, although 1-1/2" foam core would be stronger than 1" solid core, I would expect.

What I don't know if whether the 1" version will have adequate capacity, or if you'd benefit from upsizing. It's also not clear to me if the surfboard is the controlling load case, or if incidental bumps and loading should control the design.

But PVC is cheap, so if you like the idea of the smaller size and it "feels" OK, you can prototype it with 1". Worse case it fails and you decide to upsize it.

Cheers, Wayne

Thanks Wayne.

You make some good points. From what I've read the bumps on the non-paved trails add stress along with the load. In the Tim Allen overengineering department, a friend suggested buying old shocks on eBay. LMAO. The pneumatic tires supposedly help serve that purpose and one of the reasons the better designs have one solid axle vs. an independent axle for each tire. It was another reason some people said to not glue when you don't have to (just the weight of the kayak will keep verticle pieces together and/or the bolts on the axle part will keep those pieces in place) and/or use the cotter/clevis route so that you can simply replace any pieces that crack).

As you said, PVC is cheap and it is unclear if larger is better (and worth the weight if I strap it to the back and take it out with me vs. walking a distance back to the car). So, I've got the 1" and that is today's plan. I'm going to modify my design so that I can consider adding a 2nd set of wheels down the road if it needs some more load balancing and assistance with the weight.

BTW, the 1st picture shows a long piece of white PVC. That is a kickstand. Keeps the cart a little more upright when loading the kayak on it.

Thanks again. Stay safe.

 

[Mark Ezrin]

I find that the schedule 80 gray conduit, while thicker, is not really more rigid that schedule 40 white pressure water pipe. I think they put more plasticizers (softeners) into the conduit.

Thanks. Did not realize that but makes sense. As Wayne said above, PVC is cheap so I'm going to go for it. Some people have built some modified designs for even heavier kayaks like fishing kayaks.

Thanks again. Stay safe.