| Author | Message | ||
     Rickie_d |
>>>>No designer or engineer wants an ounce of weight on a bike that doesn't serve a purpose. The operative word is “wants”; however, I would qualify that statement with – If they are allowed! Too many other factors come into play to get what they want, when they want it; case in point, the use of the pulley above for so many years instead of Buell’s proprietary (nonadjustable) design. >>>>The round hole is a very important design element as some of you who studied the structural engineering recall from the studies of eggs and why holes, round ones, are drilled on dragster parts rather than cutting the center out of a piece. However, once more sophisticated methods of design and analyses became available we see less round holes punched in large expanses of material (such as the HD pulley) and starts seeing minimal material with load spreading radiuses such as the pseudo honeycomb Buell designed pulley. No eggs or round holes there, or in the rotors for that matter. >>>>Buell did and lots of it. (Reference to Analysis/Data collection) >>>>Buells are tested so far beyond what a street rider will ever put them through you can not possibly imagine it. I know they did…Marty Brown used to fill me in over my dinner table regularly. What was especially interesting is the extreme real world testing of Nissin brakes and their effect on previously accepted chassis components as opposed to the casual users operating conditions. >>>If you think you can improve a product always test your changes before you come to rely on them. Damn straight…as Jayvee warns above!!! | ||
| Adsva83 |
This thread has made me interested in getting a pulley modeled up in SolidWorks. If I have a model of it I can run some FEA tests in SolidWorks to see how much material could be removed before it fails. I'm sure this has all been done already in the original design work, but I'm interested to see myself. | ||
| Rivercash |
If anyone wants to try machining a pulley but don't want to practice on theirs, I have an extra pulley for sale in the classifieds. 50 bucks, look for (misc tuber parts 98 S1W) | ||
| Scott_in_nh |
So Andy, do you think we can get a model to Adam (adsva83) since he volunteered and all... I would feel a lot better about the mod if we had some data to work with! | ||
| Blackm2 |
Doesn't someone on Badweb use that design on their bike, someone in Germany? If someone has used that design and used it well, that would be data enough for me. It is essentially an 8 spoke design like the original, just with a bit less material. | ||
| Rickie_d |
It belongs to Aaomy as he posted it here… http://www.badweatherbikers.com/buell/messages/476 23/527075.html?1262787753 Without rereading the post, I suspect it was CNC machined and he uses it, which is what I pointed out in the beginning of this tread. Then it became an apples and oranges debate on analysis and data collection between the HD pulleys, Buell proprietary pulleys, and somehow Buell brake rotors. Personally I have modified HD rotors…I have friends marketing CNC modified rotors…with no failures, and Aaomy has obviously been successful. I only warn of restraint as illustrated by Jayvee’s post, for the simple reason I have no data and no one posted any on “how far is too far”. Again, I would not hesitate to modify the HD pulley myself, and I will be for a project of my own. | ||
| Guell |
American sport bike used to advertise the modded pulleys. Not sure if they still do or not. There was a thread on here a while ago on modded pulleys and what was too far | ||
| Scott_in_nh |
I only warn of restraint as illustrated by Jayvee’s post, for the simple reason I have no data and no one posted any on “how far is too far”. Again, I would not hesitate to modify the HD pulley myself, and I will be for a project of my own. I still want to do this, but the "how far is too far" is my concern as well. This;  seems to have larger radius corners (where it failed) than this;  yet it failed! I know I have seen at least 1/2 dozen pictures of bikes with cut pulleys on here - it would be great if some of the guys running them would chime in with their experience... | ||
| Rickie_d |
Referring to my statement from last Friday…. >>>>Court started me thinking about all the forgiveness incorporated into designs where the owners can change alignment of spinning and whirring gigabobs. The pulley pictured above was designed for bikes with axel adjusters and if there is a screw, somebody is going to turn it; whether they know what they are doing or not. So…what I am saying is make sure your pulleys are aligned if you are doing to start whittling bigger holes in them. 1) when your belt is running in a channel 2) the pulley has been modified like the ones pictured 3) and your pulleys are not aligned correctly Additional stresses are applied (torsion side loads) to a pulley that is no longer designed for such variability. This is what I alluded to in that HD compensated for the misalignment that was induced by the possibility of poor axel adjustments or too tight belt…..and the much lighter Buell designed pulley is in a nonadjustable (controlled) environment. The pulley that broke, I suspect was subjected alignment or excessive tension; However the ONLY way to confirm that is to look at the situation before it is tinkered with. And that is not an opportunity that will present itself here! (Message edited by Rickie_d on February 16, 2010) | ||
| Scott_in_nh |
Thanks for the explanation Rickie. I am very anal about alignment and use vernier calipers to measure the gap. Is there a better way? | ||
| Blake |
Adam (Adsva83), " If I have a model of it I can run some FEA tests in SolidWorks to see how much material could be removed before it fails." It would be a fun exercise, but likely much more involved than initially imagined. For instance... What criteria would you use to determine the point of failure? What alloy do you use? Cast aluminum alloy, maybe A356-T6? How do we know? Side note: Compare A356-T6 to 6061-T6/T651? What is endurance limit for the material, ~13 KSI? What are the design loads? How are they applied to sprocket FEM? What is required fatigue spectrum? Is fatigue life likely to govern? What is static failure mode? What margin of safety is desired against the various failure modes? My point is that employing a FEM expecting to easily discover the governing structural mode of failure is a VERY dangerous approach to engineering such a safety critical component. Metal fatigue is a bitch. Metal fatigue in a machined cast aluminum alloy subject to repeated cyclic loading is a most seriously major bitch. (Message edited by blake on February 16, 2010) | ||
| Natexlh1000 |
Don't forget that besides the tension of the belt and torque of the engine, The pully is unsprung weight. It bounces up and over all the road crap at the same accelerations as the rest of the rim. Take that factor along with the wide heavy pulley rim on the outside and I would think that it would concentrate the forces in many strange ways every time you pop over some railroad tracks or a pothole. Finally, it's a cast part, right? Then it's a crap shoot wether or not there is a tiny bubble or other flaw in the strut that you left behind that used to be reinforced by the metal you just chewed away. Hard to make a thing cheap+durable+pretty all at once  | ||
| Adsva83 |
Blake, I was more so thinking of running the FEA tests to see where the point of failure is most likely to happen. Choosing the bolt holes as the fixed points, and then applying a torsional force will give me data as to which area of the part will fail first. This will simply point to, "Less material needs to be removed in this spot where it is most likely to fail." What would take a lot of time with physics and statics calculations takes very little time with this program. It simply spits out a picture of the part with different colors ranging from blue to red. Blue being where the part is most structurally sound, and red being where it is most likely to fail with the applied forces. Add some material back in the model in the weak spots......run the test again.....see if there is an improvement. I'm in now way thinking that it's going to tell us, "Yeah this is definitely going to work with this design." I think there are just too many variables, as have already been mentioned. But I do think it will point in the direction of where to remove material and where is more of a risk of removing material. | ||
| Blake |
"I was more so thinking of running the FEA tests to see where the point of failure is most likely to happen." What mode of failure? Buckling, tensile yield, compressive yield, shear, fatigue crack growth, what? "applying a torsional force will give me data as to which area of the part will fail first." Load is most likely introduced into the sprocket via pressure against some limited number of the teeth of the sprocket. That localized concentration of loading may well govern the failure mode. This is a job for a professional analyst. It is not trivial. And what benefit is identifying areas of lower stress if we don't know what the material capacity is or what the structural failure mode is? If you cut away material, the stresses elsewhere are not likely to remain constant; they will increase. There is likely a very good reason that the Dark Horse Moto pulley (see pic below) is machined from solid 6061-T6 billet. And there is likely a compelling structural reason for the flanges reinforcing its spokes. I'd not be cutting on an OEM sprocket.  | ||
| Blake |
"What would take a lot of time with physics and statics calculations takes very little time with this program. " I think you'd be surprised at how quickly and how accurately a good structural analyst could characterize by classical hand methods the failure modes and stresses in the sprocket. Nothing beats having the skill to actually do hand calculation of stresses. It's handy as a sanity check. I've used SW Simulation, a lot. It is a very powerful too and simultaneously a VERY dangerous tool. As with most FEM/FEA apps, garbage in yields garbage out. I'm sure you know this. I'm am a bit overzealous in cautioning all young design engineers, please be absolutely certain of the integrity of your model and its boundary conditions. Getting the pretty picture is too easy. Always remember to also check stability (buckling), and shear in addition to the typical Von Mises stresses. Always remember to carefully review and verify the integrity of your model, the element aspect ratios and other element quality parameters. Always remember to perform multiple analyses using multiple mesh densities; compare the element stresses to the contour plot stresses, especially if stress concentrations are in play and cyclic fatigue is a concern. Check displacement (stiffness). Fun stuff. I'd like to see one made with a carbon fiber composite spoke section. | ||
| Blake |
Geez! Almost forgot! Please always remember to verify the reaction forces at the constraints to ensure that they are of the magnitude and direction expected. In this especially SW Simulation can be very tricky, especially when applied torsion or moments are involved. | ||
| Rickie_d |
>>>>“There is likely a very good reason that the Dark Horse Moto pulley (see pic below) is machined from solid 6061-T6 billet. And there is likely a compelling structural reason for the flanges reinforcing its spokes.” Yup…because it is different (reinventing the wheel) from the propriety Buell design it is intended to replace; it no longer has the same structure of Buell’s pseudo honeycomb in the same environment. Hence, it needs additional/different design elements to survive in that environment. That’s intuitive, but still no data has been produced to support any example as inferior! Not that it makes any difference since the topic cannot stay focused on the modification of one pulley and its composition….again, comparing apples to oranges! The topic was never about the differences in the materials and manufacturing processes involved in late model Buell pulleys! It was about modifying the 1977 HD designed, cast aluminum, steel reinforced pulley that Buell used until they converted their proprietary design. Then again, if no one really cares...Why should I! carry on... | ||
| Adsva83 |
I got my note pad out and took some notes. I'm just a "young engineer" and have no clue as to what I'm doing. Either it breaks or it doesn't, good luck. | ||
| Road_thing |
Please always remember to verify the reaction forces at the constraints to ensure that they are of the magnitude and direction expected. Words to live by, I'm sure...  rt | ||
| Scott_in_nh |
I'd not be cutting on an OEM sprocket. Then again, if no one really cares...Why should I! carry on... I'm just a "young engineer" and have no clue as to what I'm doing. Either it breaks or it doesn't, good luck. Maybe none of you should care, but those of us on the sidelines are very interested in your conversations! Blake your warning is taken with the sincerity it was posted with and great respect for your expertise, Rickie - your knowledge and experience are appreciated and respected, Adam - we appreciate your offer to jump in and do some analysis! Remember that even if I do not have my pulley cut - others will! So with that in mind I would like to keep the engineering speak going with the understanding that there are risks... thanks | ||
| Blake |
Rickie, The point is that the DHM sprocket achieves a lot less mass compared to the old OEM version, the very idea being discussed here, no? In order to reduce the sprocket mass, DHM saw fit to include reinforced/flanged spokes and to use 6061-T6/T651, likely a much superior material grade. This is relevant to the topic here in that it instructs as to the feasibility of merely machining the same type of lighter weight pattern from an existing old style stock sprocket. The point is that if we want to start machining away a significant amount of material from the OEM sprocket, then we may well fall short in terms of structural integrity. "That’s intuitive, but still no data has been produced to support any example as inferior! " We do have data showing some designs bad. See the photos of the broken sprockets? I'd suggest that a design should be proved good, not bad. As stated previously, unless/until some idea of the design loads/fatigue-spectra, their application to the sprocket, and the material grade involved, it's impossible to make any kind of responsible statement concerning how much if any material may be removed from the topical sprocket. Some? Surely. A lot? Unlikely. Empirical investigation might prove most efficient. Set up a test stand and break one. Alter another and break it as well. Compare failure mode and load. Maintain at least 80% of OEM sprocket strength and call it okay for test purposes? It's a tough call to make. I'd not want the sprocket on my motorcycle. | ||
| Rickie_d |
>>>>The point is that the DHM sprocket achieves a lot less mass compared to the old OEM version No doubt - We can point out the hundreds of examples of pulleys made by others for various reasons out of a myriad of materials, but all are oranges to the HD apple. Which is what the subject was about…? >>>>We do have data showing some designs bad. See the photos of the broken sprockets? There are two illustrations of broken pulleys; the reason for failure is obvious on one and not so much on the other. Check out the axel adjuster position. I have also noted those that have modified and marketed the HD pulley without breakage, however refrained from introducing other basic designs made from other material. >>>> Some? Surely. A lot? Unlikely. Exactly what I have been saying …however staying focused on the HD pulley and the limitations What is was created originally for What is it used for What it IS made of And to what extent can that one be modified. FYI – HD themselves modified/marketed alternative patterns on that same pulley in the 70 & 65 tooth versions; and then even plated them….aaugghhh!!! As I coached all along, exercise restraint! | ||
| Blake |
"We can point out the hundreds of examples of pulleys made by others for various reasons out of a myriad of materials, but all are oranges to the HD apple. " I disagree. The two sprockets are very closely related, in both duty and loading, thus we absolutely can learn from comparisons. | ||
| Scott_in_nh |
How are 6 spokes loaded the same as 8? We really don't know the duty either pulley was designed to - isn't that why we are having this discussion? Has anybody here ever seen a stock pulley fail on any of the 100-120+ RWHP monsters we see here? If not - doesn't that say there is some room for modification? doesn't this heritage softail sprocket have the same construction?  Softail Pulley link To me, the proposed machined pulley in the original photo doesn't have the same rounded corners as this - should that be changed? | ||
| Rickie_d |
Blake >>>>I disagree. The two sprockets are very closely related, in both duty and loading, thus we absolutely can learn from comparisons. Even though both pulleys serve the same purpose (duty) and drive a belt, they are not subjected to the same controlled loading, so I disagree with your disagreement… Material - One is cast and the other is not as you pointed out…we are talking about a cast unit. Environment - One was built for where adjusters (alignment) come into play and the other is non adjustable…we are talking about the one in the adjustable environment. One I would modify (and do) and the other I would not (I would design my own) …The former is what we are talking about and there are documented successes. Scott >>>>How are 6 spokes loaded the same as 8? They are if the material and construction has changed (cast vs. forged, vs. billit), I-beams U-beams and such, which Blake might be pointing out >>>>Has anybody here ever seen a stock pulley fail on any of the 100-120+ RWHP monsters we see here? I have, but it is not all about RWHP! I have seen bikes with 75RWHP tear out a modified (cast) pulley because hp was trying to launch a 775lb behemoth through a clutch that did not slip >>>>If not - doesn't that say there is some room for modification? Yes, as your example below indicates, yet Javees example illustrates the other extreme…which is why both Blake and I are talking about concerns with what is too much to what. >>>>doesn't this heritage softail sprocket have the same construction? Yes, that pulley is one version of what I was eluding to in that HD themselves started to stylize from the very same casting we have been talking about…because there was room to move, within reason!!! | ||
| V74 |
this is getting very interesting,more please guys, i have been thinking of doing something like this for a while,i have a UK M2 so have a 55 tooth rear pulley,smaller dia so less material needed to be removed to get the look so should be stronger ? | ||
| Fasted |
it MAY be stronger, but does that make it strong ENOUGH??? | ||
| V74 |
thats what i am interested in before i modify the pulley, | ||
| Blake |
I'd say that if it's good on a big heavy hog bike, then it ought to be good on a Buell. Then again, is the H-D version machined or as-cast? | ||
| Blake |
"How are 6 spokes loaded the same as 8? " They likely aren't loaded exactly the same. That was not the point. The sprockets in general are loaded similarly in that they each have a load imparted to them via a drive belt acting on sprocket teeth and being transferred to the wheel hub. The magnitude of the applied loading is likely very similar. If the applied load is the same, the peak shear and bending loads internal to the spokes themselves will likely differ in inverse proportional to the ratio of the number of spokes of the two configurations, so the 8 spoke version would see about 6/8ths of the spoke internal loading compared to the 6 spoke version. The magnitudes of stresses will further be dependent on the geometry of the spokes. |
