Saturday, January 07, 2012
Digital Torque Apapter
A couple days ago I visited Harbor Freight to buy a 20A
automotive fuse tester, which I did get, however my eye also fell
on this device:
It is their model 68283 Digital Torque Adapter and is one heck of a value for $39.99 (as of 1/30/2012). It uses strain gauge technology to measure deformation of the spindle--which is very much a precision made 1/2" square drive 3 inch extension--under applied torque, and then calculates and displays that torque using the known characteristics of the spindle and magnitude of the distortion. It's claimed accuracy is ±2.0% (it says ±4.0% in the online catalog, but ±2.0% in the manual), however per the calibration sheet and my own tests it is far more accurate than that specification--here is the supplied calibration sheet for my unit, s/n EL00624:
Note: This is intended to be used ONLY with
hand tool input--NOT powered wrenches, torque or otherwise.
I performed my own testing using dead weights of known mass and a 24" 1/2" drive breaker bar (22.75" moment arm), and found the device to be easily within ±0.5% at the points I tested using 20, 40 and 60 pound weights. For example, using the 20 pound weight which with the 22.75" arm should produce 37.92 lb-ft the digital adapter displayed 37.8 lb-ft--an error of -0.31%. With the 40 pound weight (actual torque 75.83 lb-ft) the display was 75.7 lb-ft, -0.18%; or pretty damned close top the 88.5 lb-ft calibration point.
Using the 60 pound weight (113.75 lb-ft actual) the readout was 113.9 for a +0.13% error--I was frankly quite surprised to find that my simple dead weight tests so well correlated to the calibration sheet.
The unit can be set to record the peak torque encountered, or to "trace" (track we Yanks would say) the applied torque (press the P/T button to toggle between the modes). In peak mode it saves the last 50 readings, they may be recalled by pressing the M button. Contrary to the way it is phrased in the manual the last peak torque value is the first displayed when the M button is pressed, an indicator label P01 is displayed briefly then the recorded torque. Pressing the M button again proceeds to P02, etc.
It can display the applied torque in units of lb-ft, kg-m and N-m. The display unit is set by simultaneously pressing the M and P/T keys, repeatedly, until the desired unit is displayed.
A preset torque target, from 29.5 lb-ft to 147.5 lb-ft can be entered into the instrument. Then when torque is first applied the LED will light up in green until 80% of the preset torque is attained when it will turn yellow. When the preset torque is reached the LED will turn red and a piezo "beep" will sound.
I also found in testing that the rated 29.5 to 147.5 lb-ft range is only the range over which the target value can be set. The device will actually measure from 4.0 to 29.0 lb-ft with quite good accuracy. Using a 6.7 pound weight on my 22.75" arm (12.7 lb-ft) the unit displayed 12.5, for an error of -1.6% which is not too shabby.
Perhaps the listed ±2.0% accuracy refers to this full operational range of 4.0 to 147.5 lb-ft?
Because of this level of accuracy, and that as a strain gauge based device such accuracy will be well maintained unless severely overloaded (the manual says that at 125% of full scale the LED will flash red and the alarm will beep), the instrument can be used as a standard against which to calibrate mechanical torque wrenches. Testing my HF 3/8" drive wrench I found it to easily meet its ±4/0% spec, as did my 1/2" drive MAC beam wrench and a very old Snap-On "clicker" I have had for years. When testing a 1/2" drive HF clicker I have used for at least 10 years I found it to be delivering 5 to 10 lb-ft more than its setting across its range. A couple twists of the calibration screw and retesting using the digital device brought it into spec.
Also, finding that it could measure and record peak torque values in the 4 to 29 lb-ft range, I was forced to use it to check the Torque Limiting Spark Plug Socket I reported on in the Fall. At that time I had checked its accuracy using a well-calibrated 1/4" drive and found it to release at 14.2 to 14.8 lb-ft when torque was applied in a rather slow buildup as I was pulling slowly and listening for the "click". This made the dynamic friction of internal ramp and ball more of a factor in its limiting the torque applied to the plug.
Using the digital adapter to record peak torque I was able to better simulate the rotational speed at which a mechanic might use the torque limiting socket. This revealed that with a normal sort of speed the limiter produced 14.2 to 14.5 lb-ft at the plug, and that with a quicker application (still within what a mechanic might actually do) this dropped 13.5 to 13.7 lb-ft. As most, maybe all, plug manufacturers recommend 13 to 15 lb-ft for tapered seat 14 mm plugs this entirely validates the socket's value.
My only negative comment is that the buttons are a bit small for my fat old arthritic fingers, but I can live with that...
Bottom line: I highly recommend the Harbor Freight Digital Torque Adapter, at $40 it is a steal!!!
Sunday, October 30, 2011
Dynabeads Inertial Wheel Balancing
These things are amazing and actually do a better job of balancing the wheeles than any machine balance I have ever had-- I will never pay to have a motorcycle tire machine balanced again...
Thursday, August 25, 2011
High Speed Oil Consumption
AN400 K3 crankcase ventilation system:
With the crankshaft whizzing around at 7000+ RPM I can envision a sizable quantity of churned up oil being pulled out via the PCV system. When the weather cools (99.7° here yesterday, 115.9° heat index) I plan on pulling it apart and seeing what I can see...
More about DRP Sliders and Ramp Plates
You can see that the bell on the '07 plate is 6 mm shallower than on the older plate, this does not allow the fixed and movable pulley faces to separate as much. limiting the lower (numerically higher) end of the CVT ratio range. Also visible is that the plate's fingers are 6 mm further inboard than on the older plate. This prevents the fixed and movable pulley faces from moving as close to one another as they can with the pre-'07 plate; limiting the high end of the CVT ratio range.
Here are a coupe of shots of the assembled movable face, with the 18g sliders installed and fully compressed. You can see that the bushing projects 14.65 mm with the 2007 plate, and 15.95 mm with the 2003 plate--this dimension is the farthest apart the pulley faces can be. Therefore with the '07 plate the lowest (numerically highest) attaiable gear ratio is higher than that available with the '03 plate.
On the road I had the same impressions as Ray, and went back to the original ramp plate.
I had about 250 miles on a set of 18g DRP sliders when I played around with the '07 plate, and was a bit dismayed when I opened up the variator and found that the ramp plate's fingers had chewed up the sliders, this despite my having considerably radiused the fingers' hooked ends. Here's a photo of the wear, you can see the flecks of plastic worn from the slider bodies on the seal.
DRP 18g sliders after 250 miles with lightly modified ramp plate:
So, I further ground away and nearly removed the "hook" from the fingers of the stock ramp plate as can be seen in the first photo above. This reduced the slider wear a bunch, here is a photo of them taken 1200 miles after my more aggressive modification of the ramp.
DRP 18g sliders after 1450 miles, 1200 with aggressively modified ramp plate:
This was taken just after opening up the variator. You can see the much improved contact patch, and what remains of the groove worn by the ramp fingers in the first 250 miles.
The ramp finger modification did result in an additional 100 RPM or so at higher speeds, here are the numbers before (top table) and after removing most of the "hook" from the fingers:
I can live with that...
Thursday, July 07, 2011
18g DRP Sliders and Speed vs RPM AnalysisI need to get one thing out of the way right up front--WOW!!!
Got 'em yesterday and installed this morning--I put 50 miles on them just now. Assuming the wear is reasonable and I do not experience the "rolling over" of the sliders that has been reported, I have got to place these on my Must Have list of mods. As has been reported by others the rate of acceleration from a stop does feel as though 100cc has been added to the engine, and at high speeds the reduction in engine speed makes things quite enjoyable. I did experienced one very minor downside at higher speeds, more about that below.
On initial take off with moderate to heavy throttle the engine will rev to 6k and as the CVT does it's thing the little beast accelerates quite briskly; noticably faster than with the OEM rollers. Keep the throttle rolled on 'til 55 (actual, 60 indicated) and then roll it back just a bit--the CVT behaves as though it was an automatic overdrive automobile tranny, the revs drop immediately to less than 5k while you settle in at 55mph or so. You can get that added 1k engine speed back by twisting the grip and get some decent 55 to 75 acceleration.
Here are the numbers, the upper table is with the OEM rollers, the lower with the sliders:
As indicated in footnote 1, I did not get a useful observation at 30mph with the sliders. Their cam-like profile makes RPM versus mph quite variable and load dependent at low vehicle speeds--this is a good thing though, making the bike much more controllable and at the same time more responsive at those lower speeds.
The downside I mentioned earlier is that top speed has been affected by the sliders. Because of the 11% higher effective CVT gearing (numerically lower) there is also 11% less torque at the rear wheel to push the bike. On my K3 this brought the usable top speed down from a solid 90 (real, 100 on the "clock") to 82 or so (again real mph). I got it to 85 per the GPS, but it took a good 20 to 25 seconds at WOT to get that last 3mph.
The good new is that it holds a solid 75 at 6650RPM (vs. 7500 with the OEM rollers) with room to spare; I have GIvi windscreen coming in on Tuesday, it will be interesting to see what impact that has.
As others have very well documented the installation process I only clicked a few pics, here's a shot of the rollers as removed:
Something that surprised me is that the working surface is smoother than it was when I pulled them 500 miles or so ago to break the sharp edges on the drive plate.
However after running just 500 miles with the plate fingers radiused 1/64" or so they seem to have smoothed out. Another observation (unscientific using the thumbnail test) is that the synthetic used stock rollers is much softer than the sliders. With a good force I can "catch" my thumbnail on the rollers; no way on the sliders, which I assume to be latest production as they came straight from Union Material.
Here's a closeup of one that I cleaned up, it is much smoother that it was just 500 miles ago:
Before installing the sliders I took the time to hone the plate fingers with a 320m grit aluminum oxide stone--when the 2007 plate I have ordered shows up in a week or so I will get some photos of how the sliders have fared, that should be another 350 miles or so from where I am now.
So there it is, at this point I am VERY pleased with the 18g sliders. Time will of course take it's course and ultimately "tell".
And, that's all I have to say about that...
Update, I just got back from another ride--got about 110 miles on 'em now.
GPS Mount & Engine RPM vs Speed
It's just a twisted up length of 1"x1/8" aluminum flat stock, sprayed with rattle-can "wrinkle" paint. I replaced the cover screws with M4 x 16mm stainless flat head socket caps. The GPS clip mount is one that had a broken inner clamping finger, Garmin had sent me replacement; I just center drilled it and used a M5 button head cap to mount it to the bracket:
Armed with this I set out to reverse engineer the CVT ratios at various vehicle speeds with the clutch locked up. Here is what I found:
Shown here are the tire dimensions (dia = 130 * 0.7 * 2 / 25.4 + 13 = 20.17"), circumference in inches and feet, and the revolutions per mile traveled (interestingly almost exactly 1000 revs/mile). Below that are the K3 AN400 drive ratios, the "primary" being 1:1 as the CVT is driven directly from the crankshaft.
In the table I have calculated the CVT driven sheave speed for each listed vehicle speed; this is the speed in MPH divided by 60 to get miles per minute, this divided by the tire revs/mile to get the tire RPM. The tire RPM is then multiplied by the final and secondary ratios the get the driven sheave RPM.
The engine RPM is that observed on the dash tach at the indicated speed (via GPS), at a steady state speed (with a very slight headwind).
The final column shows the calculated CVT ratio, determined by dividing the engine RPM by the calculated driven sheave RPM--this represents the CVT drive ratio at the selected speed. I found it interesting that there were all very near 1:1, as this is the natural point at which drive efficiency and belt life would be optimised.
One other issue I studied was the function of the cam/spring torque multiplier mechanism of the driven sheave. The cam spiral is such that the movable face moves inward toward the fixed face (pitch increases) when the movable face rotates anti-clockwise relative to the fixed face. You can see in this photo that the movable face has rotated as far as possible anti-clockwise, relative to the fixed face, and therefore the sheave's pitch is at its maximum:
But under what conditions would this happen?
It happens when the belt slips on the fixed face but does not slip on the movable face, which has less rotational resistance unless anti-clockwise to the extreme. So under high loads/hard acceleration, when the belt slips on the fixed driven face, the cam forces the faces together increasing the pitch of the driven sheave and pulling the belt deeper into the drive sheave--against the centrifugal force of the rollers--and increasing the CVT drive ratio--numerically higher, a "lower" gear.
BTW and FWIW, I bent up the bracket using a set of these from Grizzly. Had 'em from years and in addition to sheet metal I have bent 1/4" x 1" aluminum and 1/8" x 1" steel using a heavy duty 5" vise.