UTERUS Posted September 29, 2019 Share Posted September 29, 2019 I've got a dull bit of tungsten carbide here that measures 9.5mm with 32mm of shank if that's of use? 2 Quote Link to comment Share on other sites More sharing options...
Kimjon Posted September 30, 2019 Author Share Posted September 30, 2019 That could be perfect! Thanks Quote Link to comment Share on other sites More sharing options...
cletus Posted September 30, 2019 Share Posted September 30, 2019 For interests sake https://www.google.com/amp/s/www.hotrod.com/articles/what-is-mallory-metal/amp/ 1 1 Quote Link to comment Share on other sites More sharing options...
NickJ Posted September 30, 2019 Share Posted September 30, 2019 We had some 50mm tungsten bar going through a machine not so long ago, was comically heavy trying to lift if from the crate. No reason you can't get the first order inbalance sorted with your current approach, then its only balance shaft away from perfectly smooth running....... 1 Quote Link to comment Share on other sites More sharing options...
rusty360 Posted September 30, 2019 Share Posted September 30, 2019 Sweet, cutting it into a small lenght could be fun thou! Quote Link to comment Share on other sites More sharing options...
Kimjon Posted September 30, 2019 Author Share Posted September 30, 2019 3 minutes ago, rusty360 said: Sweet, cutting it into a small lenght could be fun thou! Will an angle grinder cut it? Guess I'm about to find out??? 1 Quote Link to comment Share on other sites More sharing options...
tortron Posted September 30, 2019 Share Posted September 30, 2019 Easy to snap off in a blind hole in an engine (Snap it, it's how you remove tungsten rings) Carbide cutting disc will do it fine 1 Quote Link to comment Share on other sites More sharing options...
Kimjon Posted October 1, 2019 Author Share Posted October 1, 2019 Put the starter hole for the tungsten inserts in the crankshaft. Holes will be upsized to the correct press fit once I get the tungsten carbide. Then tested it for run out. Pretty much bang on! 2 Quote Link to comment Share on other sites More sharing options...
Kimjon Posted October 1, 2019 Author Share Posted October 1, 2019 I've googled and googled obsessively for the past week everything I can find on balance factor. My engine is basically horizontal, and unfortunately that's not to common when it comes to small engines that people tinker with. The best information tends to be RC car or boat forums and they tend to use vertical cylinder engines. The performance mods are impressive as to is the passion for experimenting with these little motors...so a lot of good learning can be gleaned from these sites. However it doesn't 100% translate to my immediate needs. There was an article on one of these websites that used a constant (K) for calculations. For horizontal cylinder engines K=0.67 and for vertical cylinder engines K = 0.75. Basically the article said the pressure within the cylinder when all things were considered made the orientation negligible. As the weight of the piston was only a fraction of the force created by the fuel/air. This makes sense. It's the only article I've found that actually qualifies it, lots of other people mentioned there would be a difference in balance factor between horizontal v vertical, but didn't give it a value. I realise that the value changes with rpm as rotational inertia and reciprocating inertia values mathematically change at different rates - so as rpms change so does the relationship between these balance points...but I'm happy to work with an average (rule of thumb) for a set value. All my reading says balance factor can range from 20% to 80%, it all comes down to the way the engine transfers the vibration through the chassis. It's more about the felt vibration and biasing it to your favor. Up/down vibration is normally less desirable than back/forward. At some point the harmonics "will feel nicer" and that's about all you can actually achieve with a single cylinder. The general consensus was around 53-55% for vertical engines gives a nice overall result in most situations. So my way of thinking is to convert the 2 constants into a percentage and then convert the vertical values to horizontal? That's the cool thing about a constant (K value) in an equation, all the other variables cancel each other out leaving just the K. So if: K(vertical) ÷ K(horizontal) x100 = % 0.67 ÷ 0.75 x100 = 89% Therefore if 55% is the most common vertical balance factor used, then to roughly convert it to horizontal it would be: 55% x 0.89 = 49% The cag motor is actually 20° cylinder orientation. So using a bit of trigonometry you could say its roughly equivalent to 93% horizontal. So adding it all together 0.93 x 0.89 x 55% = 45% corrected balance factor. So that's the goal now, I'm aiming for 45%BF. Note BF could also stand for "bullshit factor" as I realise this isn't exactly science here, more a factor of a factor of an approximation...but the numbers seem in the ballpark of what others have arrived at too...so fuck it - going to just do it and see what happens? 2 Quote Link to comment Share on other sites More sharing options...
Kimjon Posted October 2, 2019 Author Share Posted October 2, 2019 I just got this done during the last 4hrs: Roughly ground in with a dremel, then I tidied it up by sandblasting it. Came out pretty nice I think. Bearings will be replaced...don't panic... 5 1 Quote Link to comment Share on other sites More sharing options...
Kimjon Posted October 2, 2019 Author Share Posted October 2, 2019 Next I drilled in a bearing lubrication circuit on each half to feed the crankshaft bearings. And all done...with dremelled hole on bearing housing side that allows air/fuel mix to get past bearing, but not the oil seal (same as any other motor using this idea). Hope that helps prolong the clutch bearings that everyone says won't last if using a FCC in this style motor? Time will tell I guess??? Then I chucked the dome on (no internals) just to see what the overall look will be like. 1 Quote Link to comment Share on other sites More sharing options...
Kimjon Posted October 2, 2019 Author Share Posted October 2, 2019 Mmmm, boost ports....mmmmm 3 of them.... plus extra large transfer ports making this a 5 intake port motor, all nicely port matched with good flow. Compared to a standard cylinder with only 2 transfer ports. 5 Quote Link to comment Share on other sites More sharing options...
Kimjon Posted October 2, 2019 Author Share Posted October 2, 2019 Playing around with ideas. Though I'm not sure if its worth the effort? 4 Quote Link to comment Share on other sites More sharing options...
63Ragtop Posted October 2, 2019 Share Posted October 2, 2019 You're a fuckin madman. Keep up the good work! 1 Quote Link to comment Share on other sites More sharing options...
Kimjon Posted October 3, 2019 Author Share Posted October 3, 2019 The Reed block sucked! I put it on this motor which goes pretty sweet normally...and lost performance. Too much case volume. I knew this would be an issue on this motor, but wanted to try it out anyway. It worked...but not great. I'll still try it on the motor I'm currently making as it has a FCC and that would offset the gain in case volume...but thinking this was maybe a flawed idea to begin with??? But hey, not ever idea turns out to be a good idea... Quote Link to comment Share on other sites More sharing options...
Kimjon Posted October 3, 2019 Author Share Posted October 3, 2019 A good nights rest and feeling more positive about my reed block idea. On the FCC motor (which my test motor was not), the FCC will fill (stuff) the cases a lot more than a stock half crank does. Plus I'll fill this area shown in red to further stuff the case. This was always my plan, just couldn't help trying it on a different motor first. Here's my first sketch. Unfortunately this design couldn't work for a couple reasons. I couldn't get a bolt into the area with the red shown. And my reed block was physically too large to fit inside the cases like I wanted by a couple millimeters...but if I fill the cases it will essentially achieve the same thing. So still going to try this idea on the new motor I'm currently making and see if it works out better? Quote Link to comment Share on other sites More sharing options...
Kimjon Posted October 4, 2019 Author Share Posted October 4, 2019 Cheers @UTERUS thanks so much, you're a GC for sure. No fucking around then... Hard as hell to cut. Took a full 125mm cut off disc per cut and about 2 minutes per cut...far out!!!! But got it done. 3 1 Quote Link to comment Share on other sites More sharing options...
Kimjon Posted October 4, 2019 Author Share Posted October 4, 2019 Here it is all press fitted in with loctite. Gotta be happy with that. So onwards with the build... 3 Quote Link to comment Share on other sites More sharing options...
NickJ Posted October 4, 2019 Share Posted October 4, 2019 How does it come up on the scales? Quote Link to comment Share on other sites More sharing options...
Kimjon Posted October 4, 2019 Author Share Posted October 4, 2019 1 hour ago, NickJ said: How does it come up on the scales? Balance weight was 21.25g, and I got slightly different rod values by probably taking more care leveling the rods etc. So sloppy calculations say: So 40.3%. I was hoping for 45...but will take 40.3% as it was free to achieve and is a shitload better than what I started with. I could drill more holes on the top...but for now that's going to be sweet as! 2 Quote Link to comment Share on other sites More sharing options...
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