Is there any practical reason to look for compliance in a bike frame? Seems it would be easier to dial compliance into a bike with wheels, tire pressure, and saddle than to try to make a springy frame feel more solid.

Just wondering as I went with the stiffest frame I could find and with 32 spoke Open Pro's and Michelin Pro Race tires the bike rides very nice.

Is there any practical reason to look for compliance in a bike frame? Seems it would be easier to dial compliance into a bike with wheels, tire pressure, and saddle than to try to make a springy frame feel more solid.

Just wondering as I went with the stiffest frame I could find and with 32 spoke Open Pro's and Michelin Pro Race tires the bike rides very nice.

The answer rests with you. How you feel about the ride quality is the only important thing.
For me, I get agitated with chipseal roads, so I'm looking to mitigate that road surface which there is enough of where I live.
My stiff bikes all ride "very nice." But on certain roads, I just want frame made of jello.
The stiffness I desire is tortional. I don't want the bb or chainstays to twist under load. I also don't want the fork to flex laterally, so that when I dive into a corner, I'm sure the bike will go there. I don't wan't bars and stem that flex too much when I'm pulling on them in a climb. I wan't that effort to be translated through the frame onto the ground.
Ironically, many framemakers manipulate tubes only because they look cool. The aero tubes (elongated vertically) are like a two-by-four (think about how much stiffer a two-by-four is vertically than if you turn it horizontally.) Ironically, the small benefit of areodynamics makes a bike much stiffer vertically (where you don't need it) but no more stiff horizontally, and less stiff tortionally.

One thing I never thought of, but noticed the other day, is how flexible my rear triangle is. I was following the one leg pedaling excecise recommended on Edmund Burke's "Serious Cycling" book. I was pedaling with my right foot and decided to rest my left foot on the rear wheel skewer. I noticed that every time my foot was on the down stroke I would feel the rear triangle wobble to the right, and then return when I was on the upstroke, which shows that my downstroke is obviously stronger than my upstroke. The one leg excercise is supposed to help you pedal in better circles, and this proved how far away I am from pedaling in circles... But I was just amazed at how much I felt the rear triangle wobble... I didn't do it with the other leg because I didn't want to rest my right foot on the rear derailleur, but I'd bet I'd get the same wobble. But my frame is pretty stiff, brand new. I'd only imagine how much a more complaint, or older frame would wobble... Anybody else ever do this, pedal with right foot while resting the left foot on the rear skewer? Do it and see what I mean...

Frame flex caused by the left foot is generally greater than the right. The torque exerted on a frame by the left crank is amplified by chain pull. When the pedaling force is coming from the right crank the chain partly counteracts that force by pulling back.

The answer rests with you. How you feel about the ride quality is the only important thing.
For me, I get agitated with chipseal roads, so I'm looking to mitigate that road surface which there is enough of where I live.
My stiff bikes all ride "very nice." But on certain roads, I just want frame made of jello.
The stiffness I desire is tortional. I don't want the bb or chainstays to twist under load. I also don't want the fork to flex laterally, so that when I dive into a corner, I'm sure the bike will go there. I don't wan't bars and stem that flex too much when I'm pulling on them in a climb. I wan't that effort to be translated through the frame onto the ground.
Ironically, many framemakers manipulate tubes only because they look cool. The aero tubes (elongated vertically) are like a two-by-four (think about how much stiffer a two-by-four is vertically than if you turn it horizontally.) Ironically, the small benefit of areodynamics makes a bike much stiffer vertically (where you don't need it) but no more stiff horizontally, and less stiff tortionally.
That's interesting. The roads I ride on are mainly smooth with the occasional pothole or expansion cracking. On that type of surface most anything can probably be made to ride acceptably. I can see how high frequency low impact road surfaces can influence what frame a person needs. Your comment about the aero downtube is pretty funny. My bike has one and I know I am too darn slow to ever realize any benefit it might give.

Just out of curiosity what frame are you running and does it have the type of "flex" you are looking for?

That's interesting. The roads I ride on are mainly smooth with the occasional pothole or expansion cracking. On that type of surface most anything can probably be made to ride acceptably. I can see how high frequency low impact road surfaces can influence what frame a person needs. Your comment about the aero downtube is pretty funny. My bike has one and I know I am too darn slow to ever realize any benefit it might give.

Just out of curiosity what frame are you running and does it have the type of "flex" you are looking for?

The three frames which I'm currently riding are a Look 231 (round carbon tubes with alum lugs) A Cannondale Cad5 which has a downtube that is extremely oversized but round at the bb, and a Fuji which has an aero down tube. It is tapered toward the bb, probably to lessen the vertical stiffness but the frame remains as stiff or stiffer than the Cdale even with the carbon seat stays (which may or may not give compliance.)
I also, for a short time had a scandium oversized tube Interloc with carbon seat stays. This was a great bike, super stiff, super light and compliant as the Look. I may try to replace it, but I'm thinking custom steel is in my future.

Granted, stiffness does come from materials, manner of construction and size of tubing, but I think you all are forgetting about the wheels. The same bike will ride differently with different wheelsets. A set of brand new K's will be way stiffer than a set of 32 hole 3x Open Pros.

Most of the lateral flex people feel, and equate to BB flex, comes from the wheels flexing under load.

Granted, stiffness does come from materials, manner of construction and size of tubing, but I think you all are forgetting about the wheels. The same bike will ride differently with different wheelsets. A set of brand new K's will be way stiffer than a set of 32 hole 3x Open Pros.

Most of the lateral flex people feel, and equate to BB flex, comes from the wheels flexing under load.

And tires play a role. I have 3 sets of wheels, and interchange them depending on my mood, and the ride ahead.

A set of brand new K's will be way stiffer than a set of 32 hole 3x Open Pros.

Properly built with DT comp spokes and a hub with good flange geometry, they're very close to equal in lateral stiffness. They basically only feel different.

The weakest wheel in a road wheel set is always the rear. In comparison the rear of a Cosmic Carbone is considerably stiffer than a Ksyrium.

Granted, stiffness does come from materials, manner of construction and size of tubing, but I think you all are forgetting about the wheels. The same bike will ride differently with different wheelsets. A set of brand new K's will be way stiffer than a set of 32 hole 3x Open Pros..

First, when it comes to lateral stiffness, the Open Pros are stiffer than Ksyriums. Check out the data at www.sheldonbrown.com/rinard/wheel. Plus, if you check out the link on that site to Francois Grignon's testing of vertical stiffness, you'll find that more spokes generally means greater stiffness.

Second, the amount of deflection that any bicycle wheel will have under normal riding conditions in very small compared to the deflection of fork, tires, stem, seatpost, saddle, and handlebars. I believe that most of what we perceive of the ride quality of various wheels is nothing but placebo effect.

Is there any practical reason to look for compliance in a bike frame? Seems it would be easier to dial compliance into a bike with wheels, tire pressure, and saddle than to try to make a springy frame feel more solid.

Just wondering as I went with the stiffest frame I could find and with 32 spoke Open Pro's and Michelin Pro Race tires the bike rides very nice.

All else being equal, you want the frame to be as stiff as possible. The problem is that increasing stiffness generally means increasing weight. So, you make the frame as stiff as you need for your application. Ride smoothness comes from wheelbase, fork, saddle, seatpost, stem, handlebars, and tires. Wheels are much stiffer than these components and won't make a noticeable difference in ride quality.

First, when it comes to lateral stiffness, the Open Pros are stiffer than Ksyriums. Check out the data at www.sheldonbrown.com/rinard/wheel. Plus, if you check out the link on that site to Francois Grignon's testing of vertical stiffness, you'll find that more spokes generally means greater stiffness.

Second, the amount of deflection that any bicycle wheel will have under normal riding conditions in very small compared to the deflection of fork, tires, stem, seatpost, saddle, and handlebars. I believe that most of what we perceive of the ride quality of various wheels is nothing but placebo effect.

That's all fine and well and I know that around here everything that Sheldon Brown says is akin is gospel but purely by seat of the pants feel, my SLs feel stiffer than CXP33s with D/A hubs.
My Carbones are WAAAY stiffer than any wheel I've ridden except for high flange D/A track hubs built on CXP30s.
As a previous poster mentioned, tire deflection also plays a part, as does crank stiffness, fork stiffness, handlebar stiffness, stem stiffness, blahblahblahblah...

If you like the way it rides, ride it!!!

That's all fine and well and I know that around here everything that Sheldon Brown says is akin is gospel but purely by seat of the pants feel, my SLs feel stiffer than CXP33s with D/A hubs.

Just to clarify, the lateral stiffness test info is on Sheldon Brown's website, but the testing was done by Damon Rinard. If you look through all of Damon's stuff on Sheldon's site, you'll find some very interesting data about all sorts of cycling tech.

Framebuilder Dave Kirk has a take on 'frame flex' here:http://www.kirkframeworks.com/Flex.htm

All else being equal, you want the frame to be as stiff as possible. The problem is that increasing stiffness generally means increasing weight. So, you make the frame as stiff as you need for your application. Ride smoothness comes from wheelbase, fork, saddle, seatpost, stem, handlebars, and tires. Wheels are much stiffer than these components and won't make a noticeable difference in ride quality.

stem? hmmm! some stems are smoother? hmmm!!!

All else being equal, you want the frame to be as stiff as possible. The problem is that increasing stiffness generally means increasing weight. So, you make the frame as stiff as you need for your application. Ride smoothness comes from wheelbase, fork, saddle, seatpost, stem, handlebars, and tires. Wheels are much stiffer than these components and won't make a noticeable difference in ride quality.

He has a stiff frame to sell you, and a nice piece of swamp, I mean waterfront property to sell you.

Just to clarify (after giving you a hard time.) Wheelbase refers to length of frame, correct? A longer wheelbase=smoother ride due to two things. 1) increased frame flex and 2) the rider is (more) between the wheels than on top of them.

stem? hmmm! some stems are smoother? hmmm!!!

Yes. Stems are cantilevered off of the bicycle and do deflect under load. I'm not suggesting that you buy one stem versus another because it will provide a smoother ride. I'm just saying that the amount of deflection in the stem is greater than in the wheel.

Framebuilder Dave Kirk has a take on 'frame flex' here:http://www.kirkframeworks.com/Flex.htm


I subscribe to Dave's view of the world regarding frame flex; a frame stiff though the bottom bracket and front end is going to ride firmly.

The holy grail of frames will have a stiff bottom bracket area along with a nice smooth vertical compliance. Problem is that when you beef up the tubes at the bottom bracket the ride suffers as well. Tall ovalized "aero" tubing is worst in this respect since the tube flexes more readily in the lateral direction and the tall section resists vertical flex.

As far as Todd's assertion that frames do not flex much, I generally argee but would point out that they DO flex some and a discurning rider will be able to tell the difference. For example, I have several frames with the same basic geometery that use different tubes sets and I can feel the difference between my ZeroUno frame and another built using super oversize tubing (35mm down tube and 32 mm seat and top tube). The super oversize frame has a noticably stiffer bottom bracket, which is what I wanted, but the ride is rougher as well - quite noticable. Overall, the stiffer ride is a worth while tradeoff for me since I HATE to hear chainrub when sprinting (I can't wait to try out some of the new mega size integrated cranks).

Not sure this helps but thought I'd share. :o

Ed

He has a stiff frame to sell you, and a nice piece of swamp, I mean waterfront property to sell you.

Just to clarify (after giving you a hard time.) Wheelbase refers to length of frame, correct? A longer wheelbase=smoother ride due to two things. 1) increased frame flex and 2) the rider is (more) between the wheels than on top of them.

Well, since Herons are designed for riders of various sizes who may or may not carry gear with them, they are stiff. We use oversized tubing with a thicker wall to get greater torsional stiffness. However, I think it would be difficult to find anyone who says that they ride harshly.

I think that your analysis of wheelbase is incorrect. The effect of wheelbase on ride quality is well-known to automotive engineers, and chassis flex is not really a factor. A longer wheelbase affects the rider's perception of ride quality by providing a longer interval between bumps.

Your second comment is correct in that the rider is situated further from each wheel. If the rider were located directly above a wheel, a bump of one inch would lift the rider one inch. The further the rider is from the wheel, the smaller the lift.

Finally, wheelbase also affects the polar moment of inertia. Moving mass to the ends of the vehicle will increase ride quality. However, since the mass of the rider is still centrally-located, the effect here is small.

I'm with Todd on this. I think any discussion of vertical compliance around wheels and/or non-suspension frames to be total hype/placebo. Things that have compliance in the vertical plane are tires, seatpost, seat, fork, and to some degree bar and stem. But rider position and wheelbase are HUGE factors in terms of comfort.

Yes. Stems are cantilevered off of the bicycle and do deflect under load. I'm not suggesting that you buy one stem versus another because it will provide a smoother ride. I'm just saying that the amount of deflection in the stem is greater than in the wheel.

I've felt big differences between stems on my mtb, but that's more of a handling issue and less of a comfort issue--a flimsy stem that twists and gives can be downright disconcerting in fast technical terrain. On my mtb I like to go with an extremely beefy AL stem with a beefy ti bar.

There is a very good discussion of the frame flex/compliance issue on the Serotta forum: http://www.serotta.com/forum/showthread.php?t=8595 Pay particular attention to Dave Kirk's post, I think it explains this subject very well.

There is a very good discussion of the frame flex/compliance issue on the Serotta forum: http://www.serotta.com/forum/showthread.php?t=8595 Pay particular attention to Dave Kirk's post, I think it explains this subject very well.

His example mostly deals with fork flex, which makes sense--a fork is like a spring. A frame is basically two rigid triangles. I can't see how a triangle is supposed to flex in the vertical plane. I can see that it might twist a wee tad (felt at the bb on a flexy frame) but to get vertical compliance it would have to compress, which I can't see.

His example mostly deals with fork flex, which makes sense--a fork is like a spring. A frame is basically two rigid triangles. I can't see how a triangle is supposed to flex in the vertical plane. I can see that it might twist a wee tad (felt at the bb on a flexy frame) but to get vertical compliance it would have to compress, which I can't see.
A bicycle frame is *not* a triangle, it's a rectangle with the head tube being the other side of the rectangle. As Dave Kirk stated:

"If you load a bike from above ( the way a rider does when hitting a bump) the fork will flex forward and the top and down tubes will bow. You can actually take a rigid straight edge and fix it to the bottom of the top tube back toward the seat tube. When you load the frame you'll see the top tube bow relative to the straight edge. It doesn't bend but just flexes and will of course will return to normal when you remove the load. Over load it and it will fail. Overloading it is very hard to do.

The other thing that many folks overlook is torsional flex in conjunction with vertical flex. All frames have a good bit of torsional flex. Have your flex partner sit on the frame with the bike pointed straight at the watcher. Now the flexer should twist the frame by pushing the bars to one side and the seat to the other. The frame will move a lot and it will be easy to see..........so easy the flexer should be able to see it himself from above. Much of the vertical give we feel is the head tube and seat tube moving out of the same plane. When this happens they both the seat and the bars move toward the ground just a bit......vertical movement."

Read also the reply in the same thread from Serotta James (he works for Serotta):

"Mr. Kirk is absolutely correct about testing the compliance of a frame. Vertical compliance, as we use the term, is a real and testable phenomenon. The fact is that bicycle frames are much less 'solid' than most people realize. Even the stiffest bikes bend and twist under load when being ridden. When analyzing the ride characteristics of a bike, we can usually break these down into vertical and torsional movements.

Torsionally, we examine things like drivetrain stiffness - how much will your BB and other drivetrain components deflect under X amount of force? How much is the frame twisting in response to your inputs?

Vertically, Mr. Kirk's example about the fork is very sound indeed. The frame and components of bike will move vertically under a rider's weight, and inputs from the road. Here we must tread very carefully about how we define and use the word "suspension." In the parlance of bicycles, we normally think of linkages and forks with springs in them when we hear this word. In reality, every bike is completely suspended between the axels. There is a lot of vertical movement that goes on between the two wheel contact points in any frame."

I don't think you're going to get any significant flex out of a head tube.

This is the part I'm having trouble with:

Much of the vertical give we feel is the head tube and seat tube moving out of the same plane. When this happens they both the seat and the bars move toward the ground just a bit......vertical movement.

So what is happening, the tubes are elongating and compressing?

I don't think you're going to get any significant flex out of a head tube.

This is the part I'm having trouble with:

torsional flex.. a confortable, efficient frame has a level of desired torsional flex like you once mentioned: good bb flex. steel gives a good spring. ti can rebound in a disconcerting way and aluminum doesn't like to flex.
vertical compliance? maybe vibration soak up on both triangles..

I don't think you're going to get any significant flex out of a head tube.

This is the part I'm having trouble with:
The head and seat tubes are moving out of their planes *because* the top and down tubes are bowing slightly. The head and seat tubes are the levers causing top and down tubes to flex.

Another way to visualize this would be to imagine the bike crashing into a wall. The result would be the down tube buckled inward and the top tube bowed upward. If a very heavy weight were to be placed on the seat, the buckling/bowing would be in the opposite direction with the top tube buckled downwards and the down tube buckled outward. The head tube/fork is the lever with the longest arm, therefore exerts the most force on the top and down tubes. It's the movement of those two tubes, caused by the leverage of the head tube and seat tube, that gives 'vertical compliance'.

The head and seat tubes are moving out of their planes *because* the top and down tubes are bowing slightly. The head and seat tubes are the levers causing top and down tubes to flex.

Yes and no. This is what happens in basic line diagram computer simulations. In these simulations, the forces applied are greatly exaggerated to illustrate where the stresses are in the frame. This is useful to gain an understanding of the mechanics involved, but it does not mean that there is significant deflection of the top and down tubes under normal riding conditions.

In addition, most fork flex occurs at the crown and in the steerer. There is no need for the top tube and down tube to flex to get sufficient fork flex. Now, if the fork were infinitely rigid, this would be the only way to get the fork to deflect. However, in most applications, the fork is flexible enough that top and down tube deflection is unnecessary.

Read also the reply in the same thread from Serotta James (he works for Serotta): [snip]

"In reality, every bike is completely suspended between the axels. There is a lot of vertical movement that goes on between the two wheel contact points in any frame."

You can expand this to say that there is a lot of movement, vertical and otherwise, that goes on. That does not mean that any of this movement is desirable. I have witnessed manufacturer testing of this phenomenon in various test fixtures. With exaggerated loads applied, the deflection is significant. In most cases, the intent of the testing is to determine how to reduce this deflection without adding excessive weight. For most riders, however, the trade-off of an extra half-pound in return for additional torsional stiffness is a good one.

For most riders, however, the trade-off of an extra half-pound in return for additional torsional stiffness is a good one.

On what basis? If you had said the trading a half-pound in return for greater strength, I'd be inclined to agree. But Stiffness? I am aware of no study that verifies the "frame flex wastes pedalling energy" meme. And I have wasted hours and hours looking. Unless there is so much bending as to affect handling, I don't think stiffness is a valid performance metric for bicycle frames. Loaded bikes and tandems obviously need stiffer frames than bikes designed for unloaded riding, but once the frame is stiff enough to not shimmy or otherwise misbehave, is there anything to be gained by making it stiffer?

--Shannon

On what basis? If you had said the trading a half-pound in return for greater strength, I'd be inclined to agree. But Stiffness? I am aware of no study that verifies the "frame flex wastes pedalling energy" meme. And I have wasted hours and hours looking. Unless there is so much bending as to affect handling, I don't think stiffness is a valid performance metric for bicycle frames. Loaded bikes and tandems obviously need stiffer frames than bikes designed for unloaded riding, but once the frame is stiff enough to not shimmy or otherwise misbehave, is there anything to be gained by making it stiffer?

My point was that most riders (not racers) would benefit more from the extra stiffness than they would suffer from the extra weight. Many frames available today are designed as racing frames. This means that they are suitable for 160-pound and lighter riders who carry no gear. For a larger rider or one who carries gear, this can make for a squirrely bike. Adding a half-pound to these superlight frames wouldn't be noticed by most riders yet it would create a much more versatile frame.

It's a matter of making the frame stiff enough for the application.

My point was that most riders (not racers) would benefit more from the extra stiffness than they would suffer from the extra weight. Many frames available today are designed as racing frames. This means that they are suitable for 160-pound and lighter riders who carry no gear. For a larger rider or one who carries gear, this can make for a squirrely bike. Adding a half-pound to these superlight frames wouldn't be noticed by most riders yet it would create a much more versatile frame.

It's a matter of making the frame stiff enough for the application.

So you're talking about 2lb to 2 1/2 lb frames. Right? So are we now coming into a durablity issue, (which hasn't been touched on) or are you continuing with the stiffer is better theme?

As an aside
- Interestingly enough, I've repetedly read comments by reviewers (no personal knowledge) that the new super light carbon bikes coming out over the past year are "stiffer" and have a harsher ride because the carbon "cloth" is woven tighter, allowing tubes to be made thinner. Blah, Blah, Blah. (This is not a new subject or tangent I'm hoping to discuss.)

This thread has covered alot of ground. I've got to say it has been the most interesting one so far. These are the couple of ideas that I've found the most interesting and useful.

Dave Kirk's website sure has posed some interesting hypothosis. Tortional flex at the is not energy lost, (especially at the bb-chainstays) and may contribute to helping keep the rear wheel on the ground, actually improving energy transfer.
Longer wheelbase/chainstays (like Lemonds and Merckx) improve ride comfort and improve rear wheel contact in decending and cornering especially on uneven surfaces.


Still a bit of disagreement on the validity of vertical "compliance." Does it exist? Don't know if this one will get hashed out fully.








:)

Jumping in late here, but a thought for you all to chew on. When we talk about vertical compliance of frames (or wheels, seat posts, etc.) we always think of "how much deflection from a vertical force vector" or something like that. This is the kind of thing that can be measured easily with the right equipment in a controled circumstance. However, in the real world of riding the bike, you almost always have a force vector on an angle other than perfectly vertical. Given a hypothetical frame that had "zero" vertical compliance but some quantifiable horizontal compliance, the frame would still reduce the vertical component of the force vector as it deflected sideways. So, the frame is actually going out of plane as it is deflected by road forces and therefore shows compliance even when it is stiff as a rock in the purely vertical direction. This goes a ways, I think, to explaining why there is a significantly different compliance feel from one frame to the next, even when they seem equally (and very) stiff in the vertical direction. Same applies to wheels, seat posts, etc. Just some thoughts.

This goes a ways, I think, to explaining why there is a significantly different compliance feel from one frame to the next, even when they seem equally (and very) stiff in the vertical direction. Same applies to wheels, seat posts, etc. Just some thoughts.

I tend to think that the differences in "feel" between frames, usually attributed to "vertical compliance" is really a function of the frame's resonant behavior. It's a frequency domain phenomenon. Note also that the human brain's signal processing "software" is very good at resolving complex harmonic structures. Even if the frames were deflecting significantly in the vertical plane, which they don't seem to be, these structures are made of materials with very low damping. We make bells out of metal for a reason. Absorption of energy through bending doesn't seem like it would be mch of a factor. FWIW, that's also why "frame flex wastes pedalling energy" never made much sense to me.

--Shannon

Hey, I like Shannon's and Kerry's posts. I think most of the "feel" or the bike has to do with it's lateral stiffness (and the front/aft stiffness of the fork). I don't think any bike has any real compliance in a purely vertical plane.

Hey Shannon, have you seen Keith Bontrager's lengthy treatise on "stiffness"? It used to be on his web site but it seems like it's been removed. In short, he argues that there really is nothing to the frame flex = wasted energy theory.

However, in the real world of riding the bike, you almost always have a force vector on an angle other than perfectly vertical. Given a hypothetical frame that had "zero" vertical compliance but some quantifiable horizontal compliance, the frame would still reduce the vertical component of the force vector as it deflected sideways. So, the frame is actually going out of plane as it is deflected by road forces and therefore shows compliance even when it is stiff as a rock in the purely vertical direction.

You've nailed it. Think about all the points of pressure on a frame and the angles of that pressure as you are diving into a corner, and the variables, In the saddle, out of the saddle.
It's a good reason to buy a lot of bikes and spend a few thousand hours sorting these things out.

Hey, I like Shannon's and Kerry's posts. I think most of the "feel" or the bike has to do with it's lateral stiffness (and the front/aft stiffness of the fork). I don't think any bike has any real compliance in a purely vertical plane.

Hey Shannon, have you seen Keith Bontrager's lengthy treatise on "stiffness"? It used to be on his web site but it seems like it's been removed. In short, he argues that there really is nothing to the frame flex = wasted energy theory.

Keith's article was the beginning of the end for me. Engineering school and hours of research with no results were the end of the end. I cannot find any experiments to support the theory, but arguing against it is a good way to get filleted (sliced, not brazed) in the cycing community.

Given that the difference in deflection between the stiffest and most flexible frame measured by Damon Rinard was like .5", and the low loss of the materials, I'd bet that the energy wasted is in the milliwatt range, if not less.

Anybody have the math needed to extrapolate Mr. Rinard's measurements into power loss? I don't, but I'm sure interested. I could figure it out, I guess, but as an EE, it's not my "field."

--Shannon