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We have always used Roehrig Engineering dyno's. Here's a pic of our latest unit. If you're serious about being a professional tuner, my opinion is that it's a must have. We utilize both on-board data logging units as well as the Roehrig to have a complete understanding of what the bike is doing on the track as well as how the shock is behaving. For the dyno, computer, software, fixtures etc you're looking at about $20k USD in startup. You can also check out places like race car engineering classifieds for used units if you want to go that route.

www.roehrigengineering.com for more info. We use the 3VS unit which has adjustable stroke between 0.5" - 2.0" in 0.5" increments and is capable of a half meter/sec of shaft velocity. It can also perform gas tests, seal drag tests (for those of you who are wondering if the SKF seals are the real deal) and more.

Darren

Push-Moto-2011-68.jpg

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So, without me having to spend 20k to find out, what were the results of the seal drag tests with the SKF seals?

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So, without me having to spend 20k to find out, what were the results of the seal drag tests with the SKF seals?
LOL.....sorry. They're the real deal for sure. Wilkey turned me onto them and I'm sure glad he did! :bonk:

Darren

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...and is capable of a half meter/sec of shaft velocity....

is this right?

this would be very slow :bonk:

IMO you need 10-15m/s for highspeed applications, which would be approx. half of these numbers for shocks due to the linkage.

the machines I use sometimes are big as a van or bigger and they don't exceed 1m/s (not needed for their task). but even if they would, its a very strong target to

achieve that big acceleration you need for such a short stroke that shocks have

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Mark one of the itercomp dynoes does 55inches per second I think it's 3hp motor. I was talking to someone about a roehrig 2 or 3vs he said there about £6000 secondhand the one he was talking about had duty to pay on it as well, he said they are the best dynos but I looked at the inercomp they are doing the same sort of dyno for about $7500 but the strokes max is 2.25 inches, gis a call and I can tell u what the fella said about shaft speed and things.

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IMO you need 10-15m/s for highspeed applications, which would be approx. half of these numbers for shocks due to the linkage.
10-15m/s is not realistic. In the field you'll see peak velocities between 6-8m/s on the front end and like you said, those numbers are lower for the rear shock due to the motion ratio adjustment with the linkage. When you look at data from the bike the majority of the time is spent no where near those numbers. Most of the adjustments for comfort and traction come in the 3-15inch/sec range.

The thing to remember is that a dyno isn't a substitute for track/field testing but a tool for to eliminate a lot of the guessing.

Here's a link of our dyno running at a half meter for those of you who don't know what the numbers mean. I tried to embed it, but it didn't work.

Darren

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10-15m/s is not realistic. In the field you'll see peak velocities between 6-8m/s on the front end and like you said, those numbers are lower for the rear shock due to the motion ratio adjustment with the linkage. When you look at data from the bike the majority of the time is spent no where near those numbers. Most of the adjustments for comfort and traction come in the 3-15inch/sec range.

ok, I also don't think you have to test that fast, but 0.5m/s is extremely slow!

thats 1.8km/h (1.1mph), which is slower than walking.

when watching your vid I cannot believe its just 0.5m/s :bonk:

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10-15m/s is not realistic. In the field you'll see peak velocities between 6-8m/s on the front end....

Darren

These are speeds seen on MX track? Are these also true for off-road for obstacles like sharp edge rocks hit at 30mph + ?

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ok, I also don't think you have to test that fast, but 0.5m/s is extremely slow!

thats 1.8km/h (1.1mph), which is slower than walking.

when watching your vid I cannot believe its just 0.5m/s

That video is in fact a shock being run at 0.5m/sec. What you have to consider is that we're not talking about the stride of walking, but rather over short distance such as 1-2 inches.
These are speeds seen on MX track? Are these also true for off-road for obstacles like sharp edge rocks hit at 30mph + ?
Again, there are always peak velocities that are very high, but if you look at an overall lap/trail you're not seeing constant peak velocities.

Sorry for the size, but here's a velocity graph of a lap at the Lakewood National track. This is velocity data from the front fork of an A Rider on a CRF250R.

Darren

CRF250-velocity-data.jpg

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ok, I also don't think you have to test that fast, but 0.5m/s is extremely slow!

thats 1.8km/h (1.1mph), which is slower than walking.

when watching your vid I cannot believe its just 0.5m/s :bonk:

That's ~18 in/sec.

That's just enough to break into the highspeed valving if I remember right. When I worked in automotive suspension, the LS/HS threshold was around 6 in/sec at the shaft, with motion ratios generally around 1.5-2:1 with most A-arm coilver setups.

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... We utilize both on-board data logging units....

Darren

What kind of data logging you have, is it the RaceTech one, or something else?

How many channels, what sensors it uses, how many channels and what is the logging frequency per channel?

I'm in the process of building one for me (i already have one for fuel-ignition) so i want to know what are the specs of the professional ones, couldn't get much info on the off-road ones, however for road racing there are many but the position sensors are not good for long travel/dirt.

Hope i didn't asked too much :bonk:

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That's ~18 in/sec.

That's just enough to break into the highspeed valving if I remember right. When I worked in automotive suspension, the LS/HS threshold was around 6 in/sec at the shaft, with motion ratios generally around 1.5-2:1 with most A-arm coilver setups.

if you look at his datasheet, highest speeds are at 5-6m/s (if I spot it right).

so IMO 0.5m/s (approx 1m/s at the rear wheel) is no LS/HS threshold, but everyone has his own definition ...

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Sorry for the size, but here's a velocity graph of a lap at the Lakewood National track. This is velocity data from the front fork of an A Rider on a CRF250R.

Darren

thats great :smirk:

but would be even better if the curve would be labeled (jump, breaking bumps...) :bonk:

btw, by looking at this dyno it seems you need a geared motor, a load cell and a lot of time to DIY.

if you don't have a data aquisition system, there might be no sense - but if you have one :banana:

Edited by kawamaha

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"Reiger" from Holland has roehrig duno too and they show for every customer how works suspension after revalve.

But I did a lot of re-revalve after their work.

I dont have duno and I dont understand what for it need in MX

Edited by babilon

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... here's a velocity graph of a lap at the Lakewood National track. This is velocity data from the front fork of an A Rider on a CRF250R.

.......

Darren

Thank you Darren for this real life data

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What kind of data logging you have, is it the RaceTech one, or something else?
We use the Race Tech units but are currently testing some units that have transducers with accelerometers built in so that we''ll be able to gauge harshness. The new unit is a 3 channel that samples @ 125ksps. To be honest, The Race Tech unit is my favorite because of ease of setup and use, but it's not supported any longer which is a bummer. I'm actually going to lunch with Paul Thede next week and will probably hit him up for some spare parts while I'm there! :smirk:
thats great

but would be even better if the curve would be labeled (jump, breaking bumps...)

Ha! Nothing is ever good enough! :bonk::banana:
Thank you Darren for this real life data
For sure.

Darren

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Darren do u use ur 3vs to do mx forks, do u think it produces enough speed. Thanks karl

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Dynos aren't useful for tuning, they are used to see what changed from tuning and/or manufacturing of parts. Even then, you will need an electromagnetic, (non crank type) that can do at least 7m/sec full stroke. Which is big money.. The fastest speeds I have seen in telemetry is 11m/sec.. For comparison sake..pushing the forks up and down with the front brake on is about a .5m/sec...

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I think most 3hp scotch yoke dyno will only do upto 1.5meters per second.

Edited by karlace
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