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Which means "Evil Twin". Lets see your projects where you change boring into fun or create the fun from scratch.
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 Post subject: Re: Dyno
PostPosted: Sun Mar 10, 2019 5:47 pm 
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About 12" seems to be right, that kind of sets the min rpm it will test.

I figured smoothness was what the odd pattern on the Stuska was all about and why I didn't want to just assume the fixed housing on the dynomite matched the rotor....I was thinking and honestly still am that like 12 on the rotor an 13 or 15 on the stater would be be smoother than matching them....but there might be a good reason to make the mismatch a symmetrical as Stuska did.

The pressure is a little confusing....but I THINK they are using it to control cavitation. The Dynomite guys specifically say the curves are with proper water supply which they define as 60psi. They have standard 800hp and 2000+hp....1 or 2 rotors...the graphs show 1000+ and 2000+ when you go to that page but the small one they call an 800hp dyno. I asked the salesman and he said with the correct water supply he has customers getting over 1000....so I assume they just assume the people buying the cheaper unit will have a cheaper pump setup and be at 40psi not 60. The other thing he said was 1gmp per 20 ho is the min flow, 1gm/10hp is needed for max absorption...again cavitation I assume.

The other I THINK is most people end up sizing to get the low rpm and have way more brake than they need up top so it doesn't matter if they have the pressure to get full braking at higher rpm.

This whole pump think is what kind of got me to the I give up point with the gut who owns the Stuska....he's got a pair of 10hp 2 stage pumps he wants to us the VFDs...I think I convinced him 1 is already too frikin big but he's not understanding that for 1/3 the price of a VFD we can have 2 pool pumps that deliver all the water the dyno could ever want.

the guy I bought the rollers from said he had an old Stuska 100hp and it worked very well but he didn't like the manual control so he sold it. Then he used a land&sea with electronics and instantly wished he had never sold the stuska....he said he couldn't get consiatant reading on the land&sea...but it was old too so it would be the straight not toroidal design but it probably speaks to smoothness to some point.


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 Post subject: Re: Dyno
PostPosted: Sun Mar 10, 2019 7:33 pm 
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Thinking a bit....I think John had it pretty right. For the break to work it needs to pump the water, just in unuseful ways. The Stuska style brake really only do that to a point. The toroidal units do better but I'm certain thats more about the depth to height ratio than it being a toroid. I think adding a ring to the housing on a stuska style brake that leaves the channels open top and bottom would force a whole lot more water to flow between the highest and lowest energy states and beat the toridal brake performance without me having to machine toroidal passages. That's what I think I should build.....I'll draw it up anyway while I continue to think.


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 Post subject: Re: Dyno
PostPosted: Mon Mar 11, 2019 11:03 am 
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Thinking more.....I'm leaning toward something that looks nothing like a a brake I've seen so far.

I'm thinking 12" (ok 11.75" so it can be maybe from a 12x12 cut which come undersize) 7075 rotor that is very much like a pump rotor and I'm leaning strongly to single sided, just like most pumps.

The housing will be much like a pump as well. Center inlet, bearing and seals on the back, water collected on the OD...just like a pump. This would be a weldment.

Thinking about this the way a brake needs to work is it needs to move water from low energy to high and back and the better is does that the more hp it will consume. Low energy is the center, high the OD....there is a reason pumps pull from the center and discharge on the OD. I think that the difference is that instead of a diffuser on the OD I what a constant R section with vanes to stop the
water and send it back the inlet.

In my head this make the full rotor OD effective. I am a little thinking maybe I should take a little electric pump and make a small prototype to see what happens.....I think I'm right.....I think it will work.


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 Post subject: Re: Dyno
PostPosted: Mon Mar 11, 2019 2:54 pm 
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Perhaps something like this


Attachments:
Dyno Rotor 2.JPG
Dyno Rotor 2.JPG [ 49.7 KiB | Viewed 77 times ]
Dyno Rotor 1.JPG
Dyno Rotor 1.JPG [ 71.73 KiB | Viewed 77 times ]
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 Post subject: Re: Dyno
PostPosted: Mon Mar 11, 2019 3:16 pm 
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Keep in mind the whole trick is to then stop the water kinetic energy with the stator; the toroid ones make it more obvious. Look at the "ramp" near the tip - that directs the water into the stator which kills the rotational component (tangential to the vane if you prefer) while uses the outward (normal to the vane) component to sling the water back towards the eye of the rotor. Kind of the opposite of the volute of a centrifugal pump.

Edit: Oh yeah, and part of the benefit of double-sided rotor is the bearings get simpler because they don't have to take much axial loading.


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 Post subject: Re: Dyno
PostPosted: Mon Mar 11, 2019 3:33 pm 
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Yes, stop the water.

My plan is to stop it , hopefully smoothly, on the OD where the energy is highest instead of the sides and take full advantage of the rotor diameter by getting all the water to or near rotor tip speed instead of only a portion of it.....in theory anyway. I'm working on the housing now...the OD is a shaping up as tordoid to turn the flow back toward the center, it will have vanes to arrest the omega velocity while leaving the R velocity to drive flow....more flow more damping I think.

Still sketching/thinking.....a little nervous about pooling in the bottom of the housing....not sure I care.....

Edit response - i think this design even 1 sided is nearly pure radial load since the forces are acting on the OD not the side of the rotor. Just like a pump


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 Post subject: Re: Dyno
PostPosted: Tue Mar 12, 2019 12:48 pm 
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A double sided version...I got distracted so housing sill not drawn....back to housings


Attachments:
Dyno Rotor double sided1.JPG
Dyno Rotor double sided1.JPG [ 43.61 KiB | Viewed 56 times ]
Dyno Rotor double sided2.JPG
Dyno Rotor double sided2.JPG [ 102.44 KiB | Viewed 56 times ]
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 Post subject: Re: Dyno
PostPosted: Tue Mar 12, 2019 2:23 pm 
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Here's kind of what I'm thinking with the housing. The housing is kind of tall/long in the shaft direction. I wasn't concerned as a 1 sided part, but 2 sided....it would prefer double bearings guess. This might be way over-kill too....


Attachments:
Housing 2.JPG
Housing 2.JPG [ 28.99 KiB | Viewed 58 times ]
Housing 1.JPG
Housing 1.JPG [ 58.41 KiB | Viewed 58 times ]
assebmly 1.JPG
assebmly 1.JPG [ 99.18 KiB | Viewed 58 times ]
assebmly 2.JPG
assebmly 2.JPG [ 88.46 KiB | Viewed 58 times ]
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 Post subject: Re: Dyno
PostPosted: Tue Mar 12, 2019 6:37 pm 
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Oh, OK. I think I get it. Don't see any reason why that shouldn't work, but seems more complicated to machine/fabricate.


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 Post subject: Re: Dyno
PostPosted: Tue Mar 12, 2019 7:46 pm 
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Yes, too complicated and too big. Here's a much simpler one more like my fist though. I'm still not really happy so I'll play a little more.


Attachments:
Housing3a.JPG
Housing3a.JPG [ 71.88 KiB | Viewed 50 times ]
housing 3.JPG
housing 3.JPG [ 54.75 KiB | Viewed 50 times ]
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