Hi all,

As we have no rivers overhere that are of any use to build ourselves a playspot we are looking at building ourselves something like the wavebox as used in these pictures: www.ukfreestyle.com/gallery/index.php?cat=6

I'v email PeakUK about it (as they were the sponsors of this competition) and they told me they rented it from an American company.

However, we would like to have one ourselves. That is , there is an outdoor centre (Outdoor Valley, they sponsor a few freestyle paddlers like Casper van Kalmthout, Roy Hopmans and Raoul Collenteur as far as I know) and they're interested in the possibilities.

So far we haven been brainstorming about using cementmixers to provide the neccessary thrust/water but I wondered if there were more options. Are there more devices like the wavebox used in the PeakUK competition available, preferably in Europe? I'd love to see one in action and perhaps give it a try too .

Anyway, all information, ideas etc is welcome!

BT: we don't have any rivers here that we can tap so we need to pump the water artifically.

Thanks in advance & cheers,

Michiel

You'll need an axial flow pump (ie. the flow of water is along the axis of the impeller). Axial flow pumps give incredibly high flow rates but not much head. In this case you wouldn't need a big head anyway. A few metres at most which they could easily do. Contact a pump manufacturer and see that they have to offer. I'm sure the set-up would be quite costly, as would the running costs. Give it bash and get some quotes in any case. Would be worthwhile to investigate. Let me know what you turn up.

www.sulzerpumps.com/desktopdefault.aspx/tabid-365/
www.sulzerpumps.com/desktopdefault.aspx/tabid-364/

I know I'm not an engineer so perhaps my questions/remarks seem a bit silly but roughly what you'd need is one or more pumps to pump water up a few feet and a pourover to let the water fall into a basin, right?

I guess the cementmixer idea was not quite correct. There is also a type of agricultural pump that can move about one cubic metre of water per second and they are relatively cheap (around 200 euro's). A few of those would enable us to move a few cubic metres of water per second.

I'll check with the other folks to see what type of pump that would be, let's hope it could work

michielv wrote:

I know I'm not an engineer so perhaps my questions/remarks seem a bit silly but roughly what you'd need is one or more pumps to pump water up a few feet and a pourover to let the water fall into a basin, right?

I guess the cementmixer idea was not quite correct. There is also a type of agricultural pump that can move about one cubic metre of water per second and they are relatively cheap (around 200 euro's). A few of those would enable us to move a few cubic metres of water per second.

I'll check with the other folks to see what type of pump that would be, let's hope it could work

Yeah, thats exactly what you'd need.

That agricultural pump you're talking about sounds interesting. Let me know what you turn up. I know a method for a good flow rate and a low head would be a pump that actually works the same as an Archimedes screw.
www.school-for-champions.com/biographies/images/archimedes1.gif
At this theme park nearby they employ this method. Seems to be pretty effective. By 'head' I mean the distance from the inlet of the pump to the exit which could be 5 metres above, it could be 100, depending on the application and type of pump. In your case you'd need maybe 3 metres or so, depending on frictional losses in the piping system. Leave that info to the pump experts.

I found this company on the net that built a course near Paris... Interesting reading:
www.flygtus.com/17467.pdf
I noticed that they are using four 300kW motors to move around 16 cubic metres of water per second. So 300 kW on their pump moves 4 cumecs... 300 kW is a serious size motor. If you want I could calculate the running costs on eleelectricity alone. But their head might be quite a bit. Sure you wouldn't need anything that huge Keep me posted. Interesting topic. I actually did some calculations on a box a while back. Not sure where I put them

I'll check out the sites you mentioned later tonight (am still at work but couldn't resist replying).

Currently we don't need a huge setup, we've got DWD in Zoetermeer close by if we needed that. All we are looking for is a simple setup that would allow some basic freestyle moves like cartwheeling, perhaps the occaisional loop etc.

michielv wrote:

There is also a type of agricultural pump that can move about one cubic metre of water per second and they are relatively cheap (around 200 euro's). A few of those would enable us to move a few cubic metres of water per second.

I find it hard to believe that price. Maybe it's one cubic meter per minute? One cubic meter per second for EUR 200 would allow me to build a great wave for say EUR 1000 only, anywhere I like. A cubic meter per second requires a lot of energy and thus very strong mechanics. I just can't imagine one could build such a pump for only EUR 200... Would be fantastic if I were wrong of course

Pumps are very often rated in cubic metres per hour. So maybe thats the unit. Or litres per minute etc... One can work out how many kilojoules it would require to lift a certain amount of water per second as the unit for watts can also be expressed as joules per second. This will already give you a ball park figure for the energy required.

ok, so let's say i need 5 cumecs, 1 meter up....
what would that require adrian (i mean, not in mega-einstein per square second-joule, but in understandable terms )

OK, so the given information is as follows:
Q = 5 m^3/s (flow rate)
H = 1m (head)
the density of water, ρ (Greek letter Rho) is 1000 kg/m^3
and the gravitational constant, g is 9.81 m/s^2

using the simple equation to find power delivered to the water:
P = ρgHQ
we get
P = 1000 * 9.81 * 1 * 5
P = 49.05 kW (theoretical power delivered to the water)

Lets assume then an efficiency of 70% (there are graphs where one can read this information off of. This efficiency is dependant on rotational speed of the pump, flow rate and head combined and of course, the pump itself)

So, taking the power delivered to the water divided by the efficiency we get the shaft power. The power needed into the pump:

= 49.05*10^3 / 0.7
= 70.07 kW

Quite a substantial amount I'd say. Try changing the head to only 2 metres more (3m) and your final answer with the same assumed efficiency is: 210.2 kW. A significant increase. This is ignoring many other factors that only complicate this to the tenth degree.

But to get a bit of a feel for it, I'd say this is decent. I think in your normal home you could run something that would be just over 1 kW. Maybe even 1.5. Thats on 220 Volt 2 phase (110 in the USA). Obviously this system would need 380V 3 phase or maybe 525V 3 phase. Another consideration as to where it is to be positioned. Any industrial area would have access to that.


Hope this has helped a little...

Jeroen wrote:

michielv wrote:

There is also a type of agricultural pump that can move about one cubic metre of water per second and they are relatively cheap (around 200 euro's). A few of those would enable us to move a few cubic metres of water per second.

I find it hard to believe that price. Maybe it's one cubic meter per minute? One cubic meter per second for EUR 200 would allow me to build a great wave for say EUR 1000 only, anywhere I like. A cubic meter per second requires a lot of energy and thus very strong mechanics. I just can't imagine one could build such a pump for only EUR 200... Would be fantastic if I were wrong of course

Dang, my mistake, that must have been per minute (today was a busy day at work). If it were per second that pump would have been huge

Sorry folks for all the confusing stuff from my side

Anyway, I'll ask Pablo again and perhaps tell me the link to those pumps. At least I could show you what he figured out.

By the way. Just out of interest. I found a 300 kW, 415V electric motor, SECOND HAND for 25 000 Australian Dollars.
OR
A brand new 350hp (261 kW), 460 V motor for 9338 US Dollars
OR
Brand new motors from Marathon Electric with power ratings of 400 HP ( 300 kW) vary between 27 487 and 11 516 US Dollars.

Not a cheap item to be buying. And then still comes the pump which would probably be a lot more
If I won the Lotto I'd be buying some equipment for an articfical hole/wave

Lets say you took a small sea contaner a 20Ft contaner should do it. Then you add two Mercury outboard motors about 70 horse power total ( a V8 motor with a jet drive will work also ). Put a safty cage infront of and behind the motors with an automatic emergency cutoff in case someone does get sucked in. If you funnel down the exit opening to about 6 feet add some things to shape the wave and it should work. Mabe we shoul give Mithbusters a call.

70 HP is only about 52 kW. A V8 would be typically be a lot more than that. But in any case. One needs to kind of imagine two 'reservoirs' of water at different elevations to each other. Say one 'on-the-ground-' and another, higher up. Lets say the water levels would differ by 2 or so metres. One needs to get water to the top 'reservoir' continuously and the supply of water coming from the lower 'reservoir'. This would probably be done with a pump. But driving the pump could be an electric motor and indeed, as you said, a big block V8. Probably a diesel as they don't mind running for long periods of time and generally don't overheat like petrol motors.
I'm not sure if a container would safely handle being filled with water. Calculations would need to be done and approved by an engineer if this was to be used publicly as someone could be injured/killed if it burst.
Maybe you build a ditch in the ground ( read - 'swimming pool' ) and then add some earth to gain some height and build another structure next to it. Maybe a concrete basin type thing or mild steel structure ( maybe galvanise that to prevent corrosion ) or even stainless ( if budget allows ).

Just some more ideas to add to the topic. Always good to get as many ideas as possible and different opinions. And there are plenty here on Playak .
A V8 motor is a good idea and could be a cheaper alternative. Nice.

Looks like I need to add some detail to this concept.
Start with the sea container becaus it cheap and alredy has the basic shape.
An indrustial dumpster with no top might be a better choice.
You then cut a big hole in the front as a water inlet, cut the top off if it has one and remove the doors or chop the the back end off for the water exit.
You use whats left as a frame to mount the motors and the adjustable wedges to form the wave. dont forget the safty screens. Then you throw the thing in the water and start the motors. Dutch rivers are mud bottem so you would want to form the wave in the last half of the container to avoid diging big holes in the rivver. mabe trim the sides down for easy wave access. Don't forget about sharp edges and all that genral stiff.
The calculation said for 5000 L/sec would take 49KW.
By eliminateing the pump you elimnate the frictoin loss in the pump.

nitrodude wrote:

Looks like I need to add some detail to this concept.
Start with the sea container becaus it cheap and alredy has the basic shape.
An indrustial dumpster with no top might be a better choice.
You then cut a big hole in the front as a water inlet, cut the top off if it has one and remove the doors or chop the the back end off for the water exit.
You use whats left as a frame to mount the motors and the adjustable wedges to form the wave. dont forget the safty screens. Then you throw the thing in the water and start the motors. Dutch rivers are mud bottem so you would want to form the wave in the last half of the container to avoid diging big holes in the rivver. mabe trim the sides down for easy wave access. Don't forget about sharp edges and all that genral stiff.
The calculation said for 5000 L/sec would take 49KW.
By eliminateing the pump you elimnate the frictoin loss in the pump.

By doing that you've created a strong flow of current and probably nothing more. I do get what you're saying as I've stared down at the wake of a boat and you're probably trying to imitate that. Any hole in a river is caused by water dropping in altitude (may be very small), typically over a ledge, rock or usually something. This water accelerates over the object as it drops in level and as it reaches the deeper/slower moving water on the other side, the energy is has must go somewhere and it therefore 'falls back on itself', causing the hole to form. The backwash is the water going back upstream and this is the energy that has been formed by the drop. Even if it's only very small. I'm not sure how well I've explained myself. Same as a wave train. Fast moving water entering water that is deeper, slower moving. The waters energy and momentum is halted and the water kind of compresses. Like a line of people running down a hill, the person in the front slows down and all the others kind of bump into each other and come close together.

If there are civil engineers that know more about weirs and that kind of thing. Let them explain hopefully better than I can. Important concept, energy cannot be created, it can only be transfered from one form to another.

Part 3 \"wave wedges\" In order to create a wave you need something to restrict the flow and act like a big rock in the river. You would probably need two wedges on the sides to shape the width. I would start with an opening 6ft wide (2 meter). add anothere wedge on the floor about 3ft high (1 meter) that should give you a decent wave. If you want a hole you might need a wedge behind the wave to force the water up so the wave brakes and creates a fome pile. The best \"wave wadges \"would be varable devices to alow you to shape the wave.

Nitrodude, what you're describing is a miniature artificial white water course. What I was talking about was a very simple device like the ones on these pictures : www.ukfreestyle.com/gallery/index.php?cat=6

We're not trying to build us a river here, just a simple pourover that allows for some playing. Similar to the device made for the Halfweg Stoomgemaal (where they have the Paddelsup contest each year), except that you don't depend on the watermill for pressure. It would be awesome if it would be (trans)portable so it could be used in pools, at demonstrations, competitions etc.

Just to clearify it a bit further, we're not trying to compete with the artifical slalom course DWD in Zoetermeer. We want (and need) easy and affordable access to a simple playspot in a place with no white water for the next hundreds of kilometers.

Hey Michiel,

As far as the lip goes. How broad a lip would you want? Maybe 1.5/1.8/2.0 meters? I would guess the thickness of the flow to be about 100mm. Maybe a touch more. And possibly an angle of 10 degrees or so. There are basic calculations to be able to calculate the flow rate down a given slope... Small adjustments in the thickness of flow, angle and width can make a large difference. The material over which the water flows is also taken into consideration so the calcs aren't too shabby. Let me know and then I can do that too
That box is what I had in my mind too. I've seen those pics before. Sure you could do something very similar.
Sweet

Hi Adrian,

Thanks for the offer! This evening I'll dig up an e-mail I got from PeakUK about the wavebox used at the PeakUK competition, perhaps there's more information in there. They refer to the manufacturers' website but is was down at that time.

I already suggested to Outdoor Valley (the company that is interested in the possibilities of a wavebox) that they could ask a few students from the nearby Technical University (Delft is just a 20 miles away) to help out. But your help would be excellent, especially as you understand what we're trying to do here.

I guess 2 meters would be great, although that would probably depend on the power of the pumps?

More later, for now it's lunchtime and then back to work

Cheers,

Michiel

OK. using the Manning equation, assuming we have a rectangular channel on a slight angle. It's not really such a great forumla because the forumla was derived for channels that are long and assuming the water surface has the same slope as the channel bottom. Our 'channel' is merely a lip that leaves the top box/reservoir/'pool'. But I reckon it's good enough for more ball park figures.

It states:
V = (1/n) * R^(2/3) * S^(1/2)

where V = flow rate velocity (speed) in m/s
n = Manning coefficient of 0.012 for smooth steel.
R = A /P which is: A = cross sectional area AND P = wetted perimeter.
S = slope (vertical distance divided by horizontal distance)

So assuming a lip 2 meters wide and a flow of water 100mm thick on a slope of 10 degrees, we get:

R = (2*0.1)/((2*0.1) + 2) = 0.09090909 (no unit - dimensionless)

V = (1/0.012) * (0.09090909)^(2/3) * (tan10)^(1/2)
V = 7.0748 m/s - the speed of the water

Q = VA
where: Q = flow rate in m^3/s
V = flow rate velocity (speed) in m/s
A = cross sectional area

Q = 7.0748 * (2*0.1)
Q = 1.415 m^3/s (known as cumecs amongst many paddlers)

Not too bad. Change the slope to 20 degrees and the flow rate is 2.033 m^3/s.

Hey Guys
I just read your posts on the wavebox.I am looking into putting together my own set-up. Here is some info I have dug up on the subject. You will need 2 pumps 30-50 hp. Check out www.theoutsideworld.net/gallery/gallery.htm . This is a link to a shop in the States, they have a cool setup. Similar to what you want. I think?? I have found some used pumps locally around 2000CDN dollars(each) still looking for cheaper though! If I get mine set-up first I will post all the info...
Hope this might help.

Cheers Mike

Thanks for the link Mike. Always good to get some new ideas on the subject.
You say those motors are 50HP, thats about 37kW. Times two gives about 74kW. I think what the entire project comes down to, is how big is the budget and what do you really want/expect from the system. I have heard people say that the wave box from Peak wasn't that great. A higher flow rate would provide a better 'hole' but this would cost plenty of cash. It's always a toss up. Initial and operational cost.

Just out of interest, I took this photo today of a 45 kW motor at work. Using some car keys as a scale. Fairly large motor.

To add on yet again some more boring calcualtions to this growing post.

Once all this equipment is all set-up. How much will it cost you in electricity...

I tried to find out what electricity costs in the Netherlands. Seems about 20 Euro Cents per kWh. So taking a round number of 100 kW for a motor and assuming the motor runs for 1 hour, we get:

kW * hour
100 * 1 = 100 kWh (believe it or not

kWh * cost of elec in kWh
100 * 20 = 2000 Euro Cents OR 20 Euros per hour of operation.

Better round up a few mates and hit it hard for a few hours..

I looked at the outside world box which shifts 6500 gallons of water a min from 2X50hp pumps

Now I am not an engineer or even very good at basic physics any more but this is what I worked out:

6500 gallons * 4 = 26000 litres of water a min
= 26000 / 60 = 433litres of water a second = 0.0433 cumecs
lifted over approx 1m
if pgHQ = power required then

1000*9.81*1*0.433 = 424.3 = .4243kw

Which equates to .4243*1.34048 = .5688HP

where is the other 99.5hp going? Or have I made a silly error as its late at night and I have just sat an auditing exam???!
I know I have made a daft mistake I just can't spot it!!!

I am considering using an old combine harvester engine to work mine = approx 350-400hp

duckboy wrote:

I looked at the outside world box which shifts 6500 gallons of water a min from 2X50hp pumps

Now I am not an engineer or even very good at basic physics any more but this is what I worked out:

6500 gallons * 4 = 26000 litres of water a min
= 26000 / 60 = 433litres of water a second = 0.0433 cumecs
lifted over approx 1m
if pgHQ = power required then

1000*9.81*1*0.433 = 424.3 = .4243kw

Which equates to .4243*1.34048 = .5688HP

where is the other 99.5hp going? Or have I made a silly error as its late at night and I have just sat an auditing exam???!
I know I have made a daft mistake I just can't spot it!!!

I am considering using an old combine harvester engine to work mine = approx 350-400hp

Looks alright. Remember 1 US Gallon is 3.785 litres. So I got 410 l/s which is 0.41 m^3/s. At the end I got 5.4 HP. You were a decimal out on your flowrate even though you wrote it correctly in the power equation, you were one out on the power. Thats all. So if there is 100 HP into the system, looks like 94.6 HP is being lost due to various reasons... maybe...

There might be a mistake as far as the amount of water being shifted. Maybe it is more. BUT, BUT, remember the figures I calculated are only very rough figures. They DO NOT take into account the following:

The losses in the motor (frictional losses etc)
Losses in the pump itself (frictional again on the impeller vanes, the bearings, against the the walls of the pump housing)
The length of the pipes in the system (frictional again!) What type of material the pipe is made from, how rough the surface is, how many bends are in the pipe and where, how many valves are in the system.

All these factors can produce a large amount of friction in the system. I am not sure if it would contribute to such a large loss. Pumps and pipes are not really my field but I did fluid mechanics 4 and turbo machines 5 which is basically all types of axial and centrifugal compressors and turbines. The fluid being water, air, syrup, sludge, whatever. Anyway, enough rambling. Can't help you more without getting into more calculations.

If I were to guess off the top of my head, I'd say it's possible that more than 50% of the power you put into the system could be lost to various types of friction alone.

Maybe next year I'll do some more calculations. Only 2 and a half days left of work and then I can be a beach bum for 3 weeks. L8er

AdrianTregoning wrote:

To add on yet again some more boring calcualtions to this growing post.

Once all this equipment is all set-up. How much will it cost you in electricity...

I tried to find out what electricity costs in the Netherlands. Seems about 20 Euro Cents per kWh. So taking a round number of 100 kW for a motor and assuming the motor runs for 1 hour, we get:

kW * hour
100 * 1 = 100 kWh (believe it or not

kWh * cost of elec in kWh
100 * 20 = 2000 Euro Cents OR 20 Euros per hour of operation.

Better round up a few mates and hit it hard for a few hours..

Pfew, it sounds like a good reason to do something good for the environment too and involve solar panels or something.

Sure, it will cost a bit more but ion the long run it will pay off.

BTW: I just checked the local Energy suppliers' website and I think the energy costs are a bit lower: 16.5 cents per kwh so 16,50 euro per hour of operation.

Hi all,

Guess what: in an old issue of Canoe & Kayak (May 2002) I discovered a small article about the wavebox used in the UK. It turns out that particular wavebox was co-designed by Wavesport and EJ gave a few clinics with it.

The company who is interested in the wavebox to poromote freestlye and use it for demo's and competitions happens to be the Dutch importer for Wavesport so I really do hope this connection pays off

For thos interested in the article:I've got a scan at work so if you pm me your address or something I'll mail it to you.

Cheers,

Michiel

Hi,
Very interesting topic.
Check out sopac.cnawr.cz/eng/playspot_history.htm this is about artificial playspot in a former firemen's water tank.
and more technical details (in Chech) www.sopotniceeu.emartinka.cz/default.asp...rie=2&IDClanku=3

in summary:
two diesels 14.000 ccm 140kW each
water flow 4m^3/s and water speed 6m/s

Very impressive for me.

Regards
Marcin

Wow! This is something I'd love to have around here!

Awesome articles, thank you! I sent the links over to Outdoor Valley immediately!

Many thanks,

Cheers,

Michiel

hi michiel!
i really feel sorry for any devoted paddler living on flat ground like in the NL, especially when i see all the water just running down unused in the local riverbed. of course on the other hand i envy the paddlers close to the coast for all the waves they can ride. anyway, maybe you live in central NL. if i lived there, i´d stick to financeable projects first, wich i could perform right away with my friends.
like this one:
you (probably) already have a big powerstation at hand........your car!
it can surely work enough cubics per second (i´d say you don´t need 5 like posted above but rather 2 in a small spot). you get 4 frontwheeldriveaxleparts from the junkyard. they can be attached with only 2 screws each on a stand forming something similar to a typical breaktestingdevice if you mount only the metalpart of wheels on them, which have to be wider than the ones on your car. in the middle of the wheelbearings you have a \"toothed hole\" where you can put and weld fast the ends of a mississippiboatdrivething with only wheeldiameter but full length in between. your car gets up there with ordinary repairramps and the waterchannel leads under your car from the side (bridged for driving there) and goes to the pool upfront. the mississippiwaterwheel will need a closely built \"house\" over it and the ramp to the pool will have to be angled rather flat, for this design can work big amounts of water but only little hight. the mississippywheelboards are to be screwed thoroughly to a frame welded to the axle since you don´t want anything to shoot around, blocking the axle and knocking your driving car off the stand. of course the waterlevel has to be around carstandlevel for all this and you have to block the other wheels effectively.

what ya say????greetings - headsup!