Can I make my own crankshaft stud?

Can I make my own crankshaft stud? (Full Version)

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Kmot -> Can I make my own crankshaft stud? (1/19/2008 12:08:31 AM)
Bob, I have a BSE FIRE 120L. I bought it a couple years ago, used. I am just now setting it up on my test stand to run it (It has been serviced by Dub and has a new piston). I was putting on the spinner hub, and noticed there is runout. #1: Can I use a piston stop in order to remove the stud? I am concerned the stud may be in so tight that a piston stop might not be a good idea. #2: Can I make my own stud out of a common bolt? Just to save time instead of waiting for an order from Jett to arrive. My question actually, is the stud specially treated or something? Thanks, -Tom

bob27s -> RE: Can I make my own crankshaft stud? (1/21/2008 4:22:50 PM)
Hey Tom..... The prop stud should not be threaded in so it bottoms out or is in "tight". That in itself can cause run-out. The loose stud provides a tiny bit of float, such that the prop hub sits flat on the drive washer and is aligned by the drivewasher... not by the shaft/stud. When it is in there tight, the assembly and threads can force the stud to a slight angle. If it is in tight, remove it, and just thread it in so it bottoms, then back it out a couple of turns. Then install the spinner, prop, nut. You can actually use the threaded feature to adjust the prop-shaft length to some degree. Just be sure to get at least 3/8 of thread engagement at a mininmum. If the drivewasher is not sitting straight... remove it, check the cone collar below it. Make sure there is not a bit of debris in there or something. Then reinstall. It is self-aligning. The prop stud is nothing special at all. It was designed to be cheap and removable - in event of a crash, it might bend at impact, but you would not have to replace a $75 crankshaft ---- just a $2.00 drive stud. You can use long-reach setscrews from McMaster Carr (91375A609 for example) or other hardware suppliers. Those are simple and straight. And you have the hex-drive on the one end. You can also use all-thread rod cut to length, or use a bolt as you suggested. Key is to ensure the thread ends are clean and straight after cutting. As for a piston stop.... sure, you can use one. The one I use sometimes is a piece of plastic machined with the glowplug threads machined in, and it screws in to the glowplug location. I use that to get the piston to BDC for aligning/installing the QM40 counter-balanced spinners. I also have another tool (rarely used, but needed it once or thrice) which is a plastic disk... requires removing the cylinder head, inserting the disk, putting the head back on... then removing the stud or prop nut (tool was originally for installing a helicopter fan and shaft nut on a problematic installation). Let me know how things work out Bob

Kmot -> RE: Can I make my own crankshaft stud? (1/21/2008 4:43:25 PM)
Thank you very much Bob! :)

Kmot -> RE: Can I make my own crankshaft stud? (1/21/2008 6:34:37 PM)
Okay, I used a piston stop and man, that stud was jammed in there tight and torqued down! On top of that, it had thread locker. You may recall, this is the engine from the Kansas State University Aero Team and they must have been worried it would come loose, lol. So I removed the stud, wire brushed the threads and chased them with a die. Reinstalled the stud, backed off three turns and installed the spinner hub. Zero runout! :) Thanks again Bob! [sm=thumbup.gif]

Kmot -> RE: Can I make my own crankshaft stud? (2/9/2008 1:13:58 AM)
Hi Bob, I ran the engine today. All I had on hand was a Zinger 16x6. Since Dub honed the cylinder and installed a new piston I did a regular break-in type schedule. I used Powermaster with approx 8% nitro and 20% oil with the extra percentage due to added castor oil. For purposes of not getting my neighbors p/o'd at me I used this crazy looking V muffler. It is nice and quiet actually. The engine runs well. After a couple of runs and cool downs I recorded a 7400 WOT and a rock steady 1860 idle. For 8 minutes no less! Oh, I did have the glow heat on for the extended idle test. [:D] I have a question though about a small problem. Fuel leakage. At first glance, it appears to be leaking from the engine block. Fuel was puddling on the right side and in the fin area it was bubbling there. I have two theories: 1) Cracked block 2) Remote needle valve assembly leaking, and the low pressure air behind the engine is sucking the leaking fuel up to the right side. I did not think the block could be cracked. I also thought it was one piece. After break-in I was cleaning it up and looking at it I realized the block indeed is bolted together. So I was wondering if it was possible the area where the upper cylinder was machined to clear the retaining bolt may have cracked. Discounting that, and thinking about the remote needle valve again, do you think that is what it was? Fuel coming from there and collecting on the side of the cylinder? Is this something that you have seen before on the Jett? The header adapter, pipe, and couplers that I got with this motor all have silicone rubber glued all over the place. I think the university students who used this engine were trying to stop the oil getting everywhere and they must have thought it was all coming from the exhaust pipes but it is not. They probably had the same issue of fuel/oil everywhere and could not figure it out. Anyway, have a look at the photos and let me know what you think. Thanks Bob! :)

bob27s -> RE: Can I make my own crankshaft stud? (2/11/2008 2:51:07 PM)
Im glad things are working out nicely.... Yeah, sometimes the students do not always follow instructions. There are a lot of heavy-lift teams out there flying Jett power every year. Worst thing they usually do is to totally neglect the fuel system.... then they assume engine issues. The fuel... Dont worry too much about it, unless the engine is running weird. The engine normally lubricates the front bearing quite generously. There will be some bypass out behind the drive washer. It is not a defect or leak, just how it operates. It is most likely that is where the raw fuel is coming from. (you should see a q-500 engine spray! ---- my wife hates that when calling for me..) A few years back some folks got all "upset" about the front end spray on the 90L engines, and Dub switch over to a semi-sealed front bearing. Keeps most of the fuel in, and a bit less mess. Just make sure the packing nut on the remote needle is fairly snug. At worst a loose packing nut lets air in, rather than letting fuel out. The V-tech was a great muffler/pipe. I flew one on a helicopter for a while, others used the Chapman mufflers for pattern too. Probably as good as any exhaust you could bolt on there :) If you can find an installation to fly that setup ----- give it a shot. Sounds like the header/system is a bit long yet .... but you probably noticed that. With a 16x6 you should be up over 9000 rpm once you have that bit of run-in complete. We were getting 16x8 up over 9000 fairly regularly. Most of the aero teams were trying for lower rpm with BIG flat props, and the exhaust systems were tuned very long. Just for goofs, if you have a decent 17x6 or 18x6 prop hanging round ---- try that briefly on the existing V-tech setup. Just be careful not to get the engine hot.

Kmot -> RE: Can I make my own crankshaft stud? (2/11/2008 5:43:56 PM)
Thanks Bob. You are a great resource!! [sm=thumbup.gif] I am relieved about the fuel issue. So what if it's slimy. I'm a SLIMER!! lol... :D The peak temp during this run was 270°F at the glow plug.

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