Toybreaker Posted March 14, 2007 Report Share Posted March 14, 2007 Been looking at stroker cranks. the difference in price between 4mm and 7 mm is negligible. The 7mm makes more power. Is the extra cost in the crank and case work worth it? Quote Link to comment Share on other sites More sharing options...
trueraiderfan Posted March 14, 2007 Report Share Posted March 14, 2007 (edited) good question. I would like to know the answer to that as well. Gunna get a cub this next winter or fall and would like to know that as well. Edited March 14, 2007 by trueraiderfan Quote Link to comment Share on other sites More sharing options...
dajogejr Posted March 14, 2007 Report Share Posted March 14, 2007 No... Are you planning on using a stock cylinder...or cub motor? If you're gonna stroke a bike, get 4 or 10. Bigger than 4, the cases have to be trenched anyways....and the cranks are the same price for 7 or 10. For 7 or 10 mil cranks, porting will have to be changed on the cylinders (again, if OEM) as well as a special cut head...and possibility of a spacer plate. If I had to take a wild guess here, you'll get a 7% increase in power over stock with the 4 mil. Probably a 3 to 4% increase from 4 to 7%, and again 3-4% from 7 to 10 mil. Don't quote me on these numbers...they are pretty rough at best.... Quote Link to comment Share on other sites More sharing options...
theshee Posted March 14, 2007 Report Share Posted March 14, 2007 Majicmike has cut domes for a 7mm crank on a stock cylinder. Thats what I was going to do but went with the 4mm cub instead. Quote Link to comment Share on other sites More sharing options...
Toybreaker Posted March 14, 2007 Author Report Share Posted March 14, 2007 What all is involved in assembling a crank? http://cgi.ebay.com/ebaymotors/BANSHEE-CRA...sspagenameZWD1V I have a complete machine shop at my disposal and this looks interesting to me to try out. I wouldn't mind giving this a shot. Anyone here do this and will give me some instruction? Also how deep do you have to trench the cases for 10mm stroker? .200 inch where the rod swings with a .080-.125 inch clearance? Do you have the cases linebored or use a grinder/burrs and eye ball it? I have aerospace experience and holding true position of +-.0005 isn't an issue once I know what i have to do. thanks for any help i get. I am going to do this stuff while i am on deployment to IRAQ. Can't ride it but i can still play! Quote Link to comment Share on other sites More sharing options...
FireHead Posted March 14, 2007 Report Share Posted March 14, 2007 What all is involved in assembling a crank?http://cgi.ebay.com/ebaymotors/BANSHEE-CRA...sspagenameZWD1V I have a complete machine shop at my disposal and this looks interesting to me to try out. I wouldn't mind giving this a shot. Anyone here do this and will give me some instruction? Also how deep do you have to trench the cases for 10mm stroker? .200 inch where the rod swings with a .080-.125 inch clearance? Do you have the cases linebored or use a grinder/burrs and eye ball it? I have aerospace experience and holding true position of +-.0005 isn't an issue once I know what i have to do. thanks for any help i get. I am going to do this stuff while i am on deployment to IRAQ. Can't ride it but i can still play! I am curious as to what machining is required with that kit of parts? Once you get that question answered, I can walk you through the rest or the process. I may have made a crankshaft or two when I was younger. :woot: Quote Link to comment Share on other sites More sharing options...
dajogejr Posted March 14, 2007 Report Share Posted March 14, 2007 New Baltimore is 20 minutes away from me. Those crank webs are blanks...so, you'd have to have someone drill them, obviously, other than that...press and fit. And of course a quick weld on the journals. Hmm...I got a buddy that makes his own cranks, wonder if he knows about this.... And when I say drill them, I'm not talking put it in a vice and go to town with your dad's DeWalt...LOL.... :biggrin: That is a very good price..by the way. Quote Link to comment Share on other sites More sharing options...
Toybreaker Posted March 14, 2007 Author Report Share Posted March 14, 2007 New Baltimore is 20 minutes away from me. Those crank webs are blanks...so, you'd have to have someone drill them, obviously, other than that...press and fit.And of course a quick weld on the journals. Hmm...I got a buddy that makes his own cranks, wonder if he knows about this.... And when I say drill them, I'm not talking put it in a vice and go to town with your dad's DeWalt...LOL.... :biggrin: That is a very good price..by the way. I would slap them in a vice but it would be on a brideport with a DRO. And i would use a boring head or a reamer (if i have the right size). How much press fit? .001? .002? And the center line for the journal would be 32mm off the centerline of the crank. Tig or Mig weld it? (I am not going to weld it myself. It would look like a pidgeon shat on my crankshaft if I Tig'd it) Quote Link to comment Share on other sites More sharing options...
dajogejr Posted March 14, 2007 Report Share Posted March 14, 2007 I would slap them in a vice but it would be on a brideport with a DRO. And i would use a boring head or a reamer (if i have the right size). How much press fit?.001? .002? And the center line for the journal would be 32mm off the centerline of the crank. Tig or Mig weld it? (I am not going to weld it myself. It would look like a pidgeon shat on my crankshaft if I Tig'd it) If I could answer that....I'd make the cranks myself...LOL... Quote Link to comment Share on other sites More sharing options...
FireHead Posted March 14, 2007 Report Share Posted March 14, 2007 New Baltimore is 20 minutes away from me. Those crank webs are blanks...so, you'd have to have someone drill them, obviously, other than that...press and fit.And of course a quick weld on the journals. Hmm...I got a buddy that makes his own cranks, wonder if he knows about this.... And when I say drill them, I'm not talking put it in a vice and go to town with your dad's DeWalt...LOL.... You were paying more attention than I was, obviously. I didn't see that the inner webs did not have the holes for the pins in them. It does look like the snout and flange webs have pin holes in them. I am not sure what the deal with that is? Do you see any other machine work that needs to be done? Quote Link to comment Share on other sites More sharing options...
Toybreaker Posted March 14, 2007 Author Report Share Posted March 14, 2007 other than verifying that the pins are the correct size for the rod bearings and grinding them if they are not, No i can't see anything else that needs to be done. Making a couple of clamshells to hold the center section and the rod areas to keep them from getting tweaked wouldn't be too much trouble. I am just kind of curious what would be too much clearance while pressing everything together. I mean hell $230 plus MAYBE 3 hours of labor (for the first one) and i get a 10mm stroker crank. worth the effort to me. Do a step by step how to thread? Quote Link to comment Share on other sites More sharing options...
FireHead Posted March 14, 2007 Report Share Posted March 14, 2007 I would slap them in a vice but it would be on a brideport with a DRO. And i would use a boring head or a reamer (if i have the right size). How much press fit?.001? .002? And the center line for the journal would be 32mm off the centerline of the crank. Tig or Mig weld it? (I am not going to weld it myself. It would look like a pidgeon shat on my crankshaft if I Tig'd it) The dimensions on the pin holes should be such that they support a heavy interference fit which should be about .002"-.003". Using a boring head is really the only appropriate tool for this type of operation. You should TIG weld the pins to the webs. Quote Link to comment Share on other sites More sharing options...
FireHead Posted March 14, 2007 Report Share Posted March 14, 2007 If I could answer that....I'd make the cranks myself...LOL... I was hoping that someone else would be the person to pee on the parade here, but I guess it's going to be me. Machining the pin bore for one web on a manual mill with a DRO is one thing, but doing all four webs and maintaining a reasonable tolerance on the true position of the hole across all the webs is not going to be easy. If there is grinding that is required anywhere inorder to put that crankshaft together, it is going to be that much harder to do with manual equipment. I would say the bored pin holes would benefit from being jig ground, but I don't think it's 100% necessary. Beyond that, if grinding is required on any of the bearing surfaces you are probably going to need to have thos particular parts nitrided. I am not trying to discourage anyone here, but I really think that you need to know what you are getting yourself into. If I were to make up a number, i would say that 99.5% of the HQ membership to not have the ability or skill set to do this sort of machine work. I am not trying to be an elitist wank, but I think that needed to be thrown out there to help bound this discussion. If, after all that, you want to give this project a try, then I think it's a great project. If you have the means competently complete this project then you will certainly save alot of money. If needed I will be happy to help you in anyway that I can. I would be willing to put together a list of instructions for anyone who wanted to give this a try. :geek: Quote Link to comment Share on other sites More sharing options...
Toybreaker Posted March 15, 2007 Author Report Share Posted March 15, 2007 My time estimate was not counting making the jig to hold the web in place or the clamshells to keep from over pressing the pins too far through the webs. Provided i don't fubar the jig/fixture it should be a bore/chamfer/flip/chamfer operation. then press it all together and have a welder tig it for me. Probably cost me a couple of beers. I am just gald my DRO has mm/inch measurement on it. would hate to screw up the calculations. Quote Link to comment Share on other sites More sharing options...
FireHead Posted March 15, 2007 Report Share Posted March 15, 2007 My time estimate was not counting making the jig to hold the web in place or the clamshells to keep from over pressing the pins too far through the webs. Provided i don't fubar the jig/fixture it should be a bore/chamfer/flip/chamfer operation. then press it all together and have a welder tig it for me. Probably cost me a couple of beers.I am just gald my DRO has mm/inch measurement on it. would hate to screw up the calculations. You can hold the webs in a set of prismatic vice jaws and support it with a set of parallels. Pressing the crank together shouldn't need a special fixture if you take your time doing it and measure the distance between the thrust pads on the webs as you go. Your problem is going to be that once you have machined the first web, you will have dial indicate in all of the subsequent parts. There are many ways to do this, but the least difficult methods are also the least accurate (example: a coaxial dial indicator is only good for +/-.001" no matter what its rated for). Now you could make a fixture with a center and a dowl pin on it to take any positional variance acroos the four parts out of the equation, but that requires adding a small manufacturing feature to all of the webs and you may wind up being just as accurate doing that as you were if you dialed each part in individually. Either way it's alot of work. The forgings are a mixed blessing because of all this in this particular application. It actually takes alot less time if you are making small quantities of thi type of crankshaft to make the webs from billet. If you have access to a CNC mill, it also winds up being cheaper to do if you convert hours spent working to dollars. :geek: Quote Link to comment Share on other sites More sharing options...
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