Wednesday, April 11, 2012

Concrete Weights

I have been watching Craigslist for months, if not years, just waiting for a great deal on used iron weights. And I'm still waiting. Obviously you have to get legit weights at some point, but until I find that cheap stash of 45s at a garage sale or something I make due with with what I have. Casting my own weights out of concrete has made it possible to keep progressing while I continue the search for used weights.


Cost: $6 for the mold and then 5 cents a lb.
Project time: maybe an hour per plate plus dry time
Difficulty: It's just mixing cement for the most part so not very hard at all

Tools Needed:
  • Small shovel or trowel to mix and spread cement
  • Hammer
  • Scissors (to cut tape)
  • Saw or serrated knife (to cut plastic mold)
  • Wood saw and drill (optional, if you make the wood frame)
  • Empty Spray Bottle (optional but useful to spray water)
  • Caulk Gun (if you decide to use caulk and you buy caulk that needs the gun)
Materials Needed:
  • 80 lb. bag of Quikrete cement mix (I used the "just add water" yellow and black bag mix)
  • Duct Tape (optional but a cool addition so I recommend it)
  • 2 inch diameter PVC pipe
  • Round storage bin or oil pan or other round plastic container with a 15" diameter
  • Caulk (optional, you could use tape, I think)
  • Few handfuls of dirt


I cut this video down to the essentials so I won't explain the whole project step by step here, just watch the video. However, I will make a few notes below; things I didn't have time to elaborate on in the video.

A TEMPORARY SOLUTION

To me this isn't a permanent thing. Concrete is simply not as strong as we want compared to metal plates which are basically indestructible under normal use. Though concrete has high compression strength, the way forces would be applied to a plate on a bar being aggressively set down on a heavy deadlift would no doubt break the cement over time. Concrete also is not as dense. This means it will take up more space on the bar and result in less weight you can fit on your bar. It's basically like half as heavy as iron plates. So a 45 lb. concrete plate would be the same size (at least) as two 45 iron plates. That means if you could cram 800 lbs. of iron plates onto your bar, you could only cram 400 lbs. of concrete plates.

Also, I do not suggest you use only concrete plates. If you don't have any weights I do not recommend this as your solution, unless you don't plan to pull off the floor, meaning deadlifts or power cleans or rows, etc. I don't trust cement to be strong enough to handle the stress of setting down a heavy deadlift.

I suggest you have at least a pair of 45 lb iron plates, as well as the smaller increments, 25, 10, 5, and 2.5 lbs. You can make smaller increments out of wood or industrial washers. I made a post about that, look at the Project Index for it. I personally bought one of those 300 lbs. weight sets from the sporting goods store. I think that's a decent starter set. When it costs like $200 you do get a bar that will last at least a year, plus the 255 lbs. of iron plates, including all the smaller increments. So these concrete plates make a decent temporary addition to an iron set.

Eventually though you want to find some cheap used iron plates because concrete weights are not a long term solution in my opinion. Even if they hold up, you'll eventually run out of space on the bar. Now I suppose you could probably get something like 500 lbs. on the bar using a combination of iron and concrete weights. So if you never intend to deadlift more than that I guess it might be good enough.

But to me this is a temporary solution until I hit the motherload of rusty 45s from someone on craigslist or a garage sale whom doesn't care about lifting and just wants me to take the stuff away for like 50 bucks.

PRECISE WEIGHT

This I am ashamed of. I didn't put quite enough thought into it before I started the project. I basically decided on a size, a thickness, and then I poured my plates to that thickness. As a result, the two plates I poured probably aren't the same weight. Nor are they a specific precise weight. I was roughly intending them to be 35 lbs. I think they will be a little more than that after they cure. And if they both end up being the same weight it would be pretty lucky. Since I know how to do this right, I'm ashamed that I didn't do it this way. It didn't occur to me until I was already done.

I recommend you weigh out your dry cement mix. So if you want a 35 lb. plate dump 35 lbs. of dry mix into your mixing bucket. As a weightlifter I can only assume you have a somewhat accurate bathroom scale. At the very least it will be consistent so both plates will be the same. By doing this you will ensure that all the plates you cast are as close to the same weight as you can get them. This is what I should have done but I just didn't think of it in time.

As a result, though my plates will be roughly the same size, they are probably not going to be exactly the same weight. It won't be a big deal since I can just add micro plates to compensate when they are on the bar. My plates are also probably going to be a bit more than the 35 lbs. I was intending. Again not a big deal. But it's just easier if you weigh your mix. That way you'll only have to mix it up once and pour it into the mold. You will not have to mark your mold either. For what it's worth, 35 lbs. will be somewhere around 2.5 inches thick, just an FYI. I like this thickness because cement doesn't have a high tensile strength so having it thick is a good thing. I don't really recommend making light plates out of cement for this reason. They won't be as strong if you make them thin and if you make them thick but light you just waste space on your bar.

PVC PIPE

The way PVC is labeled is by the inner diameter. So when I tell you to use 2 inch diameter PVC pipe that is what it is labeled in the store. The actual outer diameter is more like 2.25 inches. So the hole it leaves in your cement plate will be 2.25 inches, which is more than big enough to fit on the bar. We make a better fit with a duct tape ring. See the video for that. I just wanted to clarify that 2" pipe is what it will be labeled as, and it will have an outer diameter of 2.25 inches.

THE EXTRACTION PROCESS

I made wooden frame to help me take the plate out of the mold by myself easily. I had the scrap wood and tools so I spent no money on it. If you don't have this stuff you don't have to make it. I'm sure there's something around the house you could use to support your plate as you tip the mold upside down. If the inner PVC pipe holds tight to the cement like it did for me in the video you might even be able to just pull the plate out using the PVC as a handle of sorts. The PVC did not hold to the cement like this when I cast me first plate though. Anyway, it's not rocket surgery here.  Point being, you don't have to spend money or time making that "extractor" if you don't want to. I only did it because I had the stuff and I was bored and figured it would make things really easy, which it did.

Also, when I cast my first plate I sprayed the mold first with some oil. The idea being that it would help release the concrete. The second plate I cast I did not do this. It doesn't seem to matter. The concrete will not stick to the plastic mold. However, I did have a hell of a time getting the PVC pipe out of the second casting. This may or may not have anything to do with not oiling it. The pipe also was a little wiggly (i guess the caulk didn't hold as well) the second time, so it may have set slightly off kilter, which is what I'm betting on. Point being, you don't need to oil it or use any kind of mold releasing agent. But if you want to spray it down with some WD-40 it won't hurt anything.

MARK YOUR PLATES

Once you let your plates cure for a few weeks I would suggest painting their weight on them. This is especially true if you messed up like I did and both plates don't weight the same amount. Mark their weight on them so you know exactly what they weigh.


INNER CORE

In the video I show you how to line the inside of the plate with duct tape to protect your bar and give it a better fit. Since then I realized there is another option. The PVC pipe you used to cast the center hole is the perfect size to slide over the bar sleeves on an Olympic bar. So you could cut down a length of that PVC the same thickness as your plate, then hammer it into the center. It will fit very tightly. As you saw in the video I had a hard time getting the pipe out of the plate when unmolding. I had just a hard of time hammering in the new shorter length of pipe. I'm not sure how this will affect the plate in terms of the concrete expanding. But it fits beautifully on and off the bar with ease.I would say the PVC core is nicer, assuming it doesn't have some unforseen negative impact on the expansion of the concrete.

That being said, using concrete plates is a temporary solution so you want the price to be as low as possible. I had the scrap PVC so decided to try it out.


- Carl

12 comments:

  1. Got 600 pounds in Oly plates, 2 7' Oly bars and 1 EZ-Curl Oly bar for $200, negotiated down from $300 on Craigslist at the beginning of March. Got a power cage and 750-lb capa bench for $300 two weeks later. Not posting to rub anyone's nose in it, I'm just trying to make the point that deals are out there, you just have to call and try negotiating. No one's going to give you their lowest price to start off with - that's Common Sense 101.

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  2. Good ideas but lets say you don't have a bar.. what do you use for a homemade bar? I'm new to weight lifting and currently use heavy duty resistance bands. I have 60 and 100 lbs of weight resistance with these but I want to try free weights because the load is reversed. I am looking at 40 lbs vinyl covered cement dumbbells from gold's gym from walmart - 20 bucks and the 100 lbs vinyl covered cement barbell set - 49 bucks. Problem is, I dont have the 70 bucks. These are standard sets so they use 1 inch bars and 1 inch holes in the plates. I would need to find some good material for the bars that are 1 inch. Because these vinyl plates are so cheap, I plan to make cement plates to use with them for extra weight - and then not use their bars.. use the homemade bars I make. In other words, I need to make my complete homemade set with cement plates and homemade bar and the 1 inch dumbbell and barbell set from walmart reverse compatible. It will be a while before I can buy these sets but when I do I still want to be sure I can use them together. Any ideas on a homemade bar material for this?

    Also, if you can find a pvc sleeve that fits your bar, why not use that instead of tape in the middle of the plate? You could cement or hot glue this in the hole.

    I think it would be neat if someone discovered common plastic molds that allow you to more easily make your desired weights so they would come out to match better. You could have a whole range of weights in this manner, just like buying a regular set, for a fraction of the price.

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    Replies
    1. Don't spend $70 on 140 lbs. of vinyl weights. Take that $70 and put it toward a used Oly bar and weights. A 300 lb. set retails for $200. People sell them for half price. You could probably get them down to $70 or get them to sell you just the bar and less of the weights. The fact is, for $70 you can get an Oly bar and some iron Oly weights so to spend it on vinyl weights would be the worst thing you can do. Even if you are adamant on standard sized stuff and vinyl plates you should still buy them used. You'll get way more for your money.

      But I recommned you just save up and buy an Oly bar and iron plates. Like I said if you're going to spend $70 you can get Oly stuff. You will have to find a seller but when it comes to used weights these Oly 300 lb. sets are pretty common. The problem I have is that I want only 45 lb. plates. Most people don't have a stack of 45s because people who sell used weights usually weren't serious about lifting. They buy those starter sets, don't lift, then sell them. People who have stacks of 45s are serious lifters and they typically want to get a lot of money for their stuff.

      Point being, you won't have too hard of a time finding used Oly weight sets. I know that's the generic answer but it is your best option. You are even better off buying the set retail for $200 than buying the vinyl stuff.

      But to answer your question, there is no good way to DIY a normal barbell. The diameter of the bar is too small, so it needs to be solid steel, and of decent quality. Otherwise it will bend and stay bent. You can't buy this at the local hardware store, and even if you could it would cost probably 20 or 30 bucks. Money that could buy you a real used Oly bar.

      Regarding making a full set of cement plates they aren't strong enough. Cement has shitty impact strength and shitty tensile strength. What it's good at is compression strength. And that's the least of the qualities you need in a weight plate. There's really not any compression stress on a plate on the bar.

      As far as the PVC goes I mention that at the end of the article. I made the video before I realized the pipe fit over the bar. I know this might not be the answer you want but it's the correct one. Buy what you really need so you won't regret it later. The less money you have the more important it is to use it wisely.

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  3. If you line your mold with plastic, you can just pop it out and reuse the mold. That would radically cut down on the cost per weight to almost nothing. They might have some ripples in the side, but since you're making your own, it doesn't seem like you care to much about the looks of your weights.

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    Replies
    1. Cement doesn't stick to smooth plastic. If you use a plastic mold cement won't stick to it anyway so you don't have to line it with anything. But if you used a metal mold you would be right, line it with a plastic garbage bag. it will indeed get ripples, I've done it before, but like you said, who cares. I didn't line the mold I used in this video because it's plastic to begin with.

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  4. - Matt asked, on youtube, how long these plates will last and whether or not I should reinforce them with rebar to make them stronger. Here is my reply:

    Hey Matt,

    These can last for years depending on how you use them / treat them. Making stronger plates is not necessary for me because I have some iron plates too so these concrete plates don't hit the ground when I deadlift. The way I use them they will last for years, and I'll end up busting them up and throwing them out when I get more iron plates, whenever that may be. If you were building a true "third world gym" then that would be different but there's no point for me to make stronger DIY weights.

    At the end of the day that just costs more, is more work, and they will still take up too much room on the bar. Once I deadlift 405 there is no choice but to get more iron 45s. That is a goal most younger people can do in about 3 years of GOOD training. I think these plates could last that long if you treat them well. The big problem is concrete plates simply take up too much room and they aren't heavy enough for all the space they take up.

    Yes you could put rebar in them and I've even seen someone encase them in wood. But once you get strong it's not an option anyway. So I say just be careful, use them in conjuction with iron plates and they will last long enough to serve their purpose even if you don't reinforce them. But like I said, if you've got a true third world gym going on then you basically use anything you can, including car parts, to get weight on the bar.

    Just keep in mind that there are three basic kinds of stress: tensile, compression, and impact. Tensile is like snapping a twig in half, impact is hitting the object with another object, and compression is putting a static load on top of the concrete. Concrete is great at handling compression, Rebar makes it better at handling tensile stress. But impact would be the main stress involved in barbell lifting. And really that comes into play when pulling the bar off the floor (or rather slamming it back into the floor when you put it down). Besides that there isn't much stress on the plates. So if you have at least two 45 iron plates you can use then making smaller concrete plates won't touch the ground when you pull off the floor. I have found no need to reinforce them because when all is said and done they will last until there is no more room on the bar and I will have to get iron plates to continue lifting heavier anyway, no matter how strong the cement plates may be.

    fwiw I have some 25lb cement plates that are at least a year old, so old I can't remember when I made them. ANd they are just as good as the day I made them because I take care when using them. They really will last until I bust them up with a hammer when I don't need them anymore. But if you don't have iron 45s to use when pulling off the floor I don't know how long they would last, even if you reinforce them. Like I said impact stress would be the factor there and I don't know a simple and cheap DIY way to solve that problem.

    Also, before someone says it, atlas stones are different because of their shape and mass.

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  5. http://www.calculator.net/concrete-calculator.html?slablength=5&slablengthunit=foot&slabwidth=2.5&slabwidthunit=foot&slabthick=5&slabthickunit=inch&slabquantity=1&holediameter=12&holediameterunit=centimeter&holedepth=3&holedepthunit=inch&holequantity=2&holecal=Calculate&tubediameter=5&tubediameterunit=foot&tubeindiameter=4&tubeindiameterunit=foot&tubedepth=6&tubedepthunit=inch&tubequantity=1

    ^ link to a cement weight calculator

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  6. A couple of observations which may provoke some extra thought if I may.

    The final weight of concrete will always be above the dry weight of the ingredients. Water is absorbed into the material as the concrete sets and this does not ever escape through evaporation. Most of it is not sitting free within the material to slowly evaporate as it dries, it is chemically bonded as part of the concrete's structure itself. I found on a professional materials site, (http://www.lmcc.com/concrete_news/0307/hydration_and_strength.asp), that the usual rate is as high as 45lbs of water to 100lbs of dry mix. Then a small evaporation allowance should be included on top. I think this amount of accuracy is overkill but it shows that you should factor in some considerable extra weight for the water.

    I think you are being hard on yourself when you talk about your lack of precision in designing. It isn't really incredibly important unless you are on a strict regime where you accurately increase by a pound or two regularly. As long as you know what weights you have and they are balanced in pairs you would be able to successfully train and improve. A couple of pairs of heavy matched discs of around your 35lb target, mixed with a few smaller iron discs to increment would be fine to train with. Weighing out a larger wet mix into a pair of moulds while each is on the scales should allow you to get an accurate balance. You should then get the same amount of wet mix in each and it should evaporate to the same weight as it is from the same batch. Hey presto, a pair of matched discs.

    As far as strengthening the concrete to cope with impact and tensile loads, one common easy way is to insert a couple of flat rings of simple chicken wire into the mix as you mould. Construction bars are not necessary, we are not talking about taking huge loads here, just really carrying their own weight with the odd bump. The wire only needs to be rough cut to stay within the concrete surface and inserted at stages as you build up your flat disc. It may even be easier to simply overlap a number of smaller pieces as you build up. The wire is perfectly capable of taking some of the tensile load as do bigger bars in major work, which of course are relatively small in comparison. And even if the disc then does crack the wire will hold it together.

    Another additional way to make the discs more robust and versatile would be to mould them within a rubber tyre or ring so the edges are cleaner and constrained. I'm looking for materials and a method to do this at the moment. There is then less shock to the disc during handling and it's kinder to wooden floors too!

    Why not simply leave your central plastic tube in place after moulding and trim it down in place with a saw? It seems unnecessary to knock the tube out then insert it again. If you left a mm or two of tube standing proud you would even have a natural spacer between weights to stop them from banging together and grinding against each other in use.

    In truth, I think the vast majority of people are not going to be in the 800lbs class of lifter. They just want 200lbs at most for general training rather than lifting. Concrete weights do provide a permanent solution for this. (Particularly if they aren't just interested in impressing their friends with the professional look of their setup.)

    Great article and a really sound starting point for this project. Thanks for the info.

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  7. can i use something else instead of the pvc pipe?

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  8. The concrete will be a lot stronger if you add some chopped fiberglass to it

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  9. You can get concrete round molds in the size (8" to 16" or even bigger) pretty cheap at many hardware stores, and you could also get PVC with an inside diameter of just about 2" (2" inside diameter is about 2.067" with 2.375" OD), scrach up the outside of the pipe and just leave it in, cut it to size after the concrete sets. I've been researching myself and I'll probably make some this month over the summer, you don't need steel plates at all unless you are going above 400 lbs, which takes several years.

    According to the calculator posted above, 16" diameter by 3" deep is about 45 lbs each, a layer of chicken wire in it will definitely help hold it together longer, but it doesn't have to be an issue, I plan on grabbing cushions off of my cheap couch to drop onto when I need to drop. Pretty easy.

    That set up can get let you make 400 lbs of weight for under 50 bucks. I plan on grabbing a couple 8" extra tubes to fill with concrete, then putting a dip in the top to use for a cheap bar holder and to make a bunch of dumbells at various weights as well. You can't beat the price.

    If you step up to 22" plates you can fit as much as 750 on a bar, but you may have to stand on a block of wood or something to get the full range of motion.

    I don't know how concrete would handle it, but you could also try getting straight cement and use some kind of cheap scrap metal bits, pellets, shot for filler. That would probably get your weight pretty high pretty fast.

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  10. I personally bought one of those 300 lbs. weight sets from the ... ifreeweightset.blogspot.com

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