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Old 08-23-2013, 06:54 PM   #1
adrenal OP
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DIY dyno build

Here's the design of an inertia dyno I'm currently building:





The inertia of the main wheel has been designed to suit bikes form the last century - 70's-80's. Mainly airheads. The red wheels can be installed when more powerful bike are being tested. The build is about 70% complete..
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Old 08-23-2013, 07:22 PM   #2
adrenal OP
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lump O steel

almost 1/2 tonne K1045 steel! OD460mm x 300 wide



Drilling pilot hole for boring:



Boring to final ID:

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adrenal screwed with this post 08-24-2013 at 02:39 AM
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Old 08-23-2013, 07:44 PM   #3
_cy_
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holy cow.. what a lathe!
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Old 08-23-2013, 07:50 PM   #4
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Originally Posted by _cy_ View Post
holy cow.. what a lathe!
yeah, don't want to get your tie caught in that one!
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Old 08-23-2013, 08:14 PM   #5
crazydrummerdude
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Oh, man this is gonna be good!
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Old 08-23-2013, 09:15 PM   #6
dhallilama
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Oh, man this is gonna be good!
um. i've built plenty of my own equipment and such... but this is friggin' awesome. just. plain. awesome.
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Old 08-23-2013, 09:19 PM   #7
downdog
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You just got this stuff lying around in your shop?

Cool!
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Old 08-23-2013, 09:20 PM   #8
k-moe
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Hmmm... I was hoping to see that lump being spun on a mish-mash of trailer tires driven by a pickup on a jackstand, and you working the OD with a file. Where is the adventure in doing things the right way?
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Old 08-23-2013, 09:42 PM   #9
pommie john
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How are you going to calibrate it?
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Old 08-23-2013, 10:18 PM   #10
Wirespokes
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Dang! The initial post looked pretty unsubstantial - maybe something I could build.

No way, Jose!!
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Old 08-23-2013, 10:48 PM   #11
victor441
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VERY cool! something I'd mused about myself, will be following this with much interest...
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Old 08-23-2013, 11:38 PM   #12
adrenal OP
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Quote:
Originally Posted by k-moe View Post
Hmmm... I was hoping to see that lump being spun on a mish-mash of trailer tires driven by a pickup on a jackstand, and you working the OD with a file. Where is the adventure in doing things the right way?
I've seen those rigs - much harder to improvise like that I reckon.

@pommiejohn. good question.Inertia dynos are not hard to calibrate. A matter of calculating the polar moment of inertia of the lump and plugging into the dyno software. Then there are ways of determining friction losses through the bearings etc and plugging these into the software as well.

But as final tweak/check, after a run on the dyno I'm going to ride straight over to a 'real' dyno which I know is well calibrated and compare numbers.
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adrenal screwed with this post 08-24-2013 at 01:21 AM
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Old 08-24-2013, 12:54 AM   #13
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While better machinists than me were producing big chips, I started on the frame:









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Old 08-24-2013, 02:08 AM   #14
pommie john
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...

@pommiejohn. good question.Inertia dynos are not hard to calibrate. A matter of calculating the polar moment of inertia of the lump and plugging into the dyno software. Then there are ways of determining friction losses through the bearings etc and plugging these into the software as well.

But as final tweak/check, after a run on the dyno I'm going to ride straight over to a 'real' dyno which I know is well calibrated and compare numbers.


I remember reading that Dynojet just couldn't get the calculations to match the readings, so they measured a known bike and used that as a starting point. ( I think that's what happened).

One thing to bear in mind ( that every dyno place I've been to in Brisbane ignores) is airflow through the dyno room. A 1000cc motor on full song flows thousand of litres of air through it each minute and it needs a good supply of fresh air delivered to the room.

Most dyno operators don't seem to realise this. I was at one place and we kept getting inconsistent readings that didn't make sense. We went back to the original jetting and didn;t get the same power curve. Then we noticed that our eyes were watering and stinging and it turned out that we had used up lots of the oxygen in the dyno room and that was making it run rich. Opening the doors and flushing the room with fresh air got us back to consistent reading. We ended up running with the doors open and finally got readings that made sense.
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Old 08-24-2013, 02:35 AM   #15
adrenal OP
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.............Opening the doors and flushing the room with fresh air got us back to consistent reading. We ended up running with the doors open and finally got readings that made sense.
Interesting. Yep consistency and repeatability is key. In my book, the accuracy of the absolute HP number is far less important than knowing if your mods are heading in the right direction and by how much in percentage terms.

I've drawn up a dyno room. It has a huge ducted fan cooling the bike that pulls gob loads of air from outdoors. Sounds like a jet turbine!
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