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Prop Shaft Question - 12/12/2004 10:23:26 PM   
Kelley


 

Posts: 52
Joined: 4/18/2002
From: memphis, TN, USA
Status: offline 		I have what will probably be a dumb question about my 90BSE. This is the first engine I have owned that the prop shaft was separate from the crankshaft. The small spinner that came with the engine has a threaded prop shaft stud that screws into the crankshaft. If I want to use a different spinner do I remove the threaded stud and reuse it with a double nut or do I just go the hardware store and buy a bolt of the same size? If I need to buy a bolt, what is the thread size?
       Post #: 1

RE: Prop Shaft Question - 12/13/2004 3:45:32 PM   
bob27s



Posts: 4637
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Hi Kelley,

Thanks for writing.....

There are never dumb questions However, I think you may be a bit confused. Sounds like you may have the prop stud bottomed out in the spinner nut, and have assumed that they are an 'assembly' that stay that way. Not true. Seperate the stud from the prop nut (use several layers of tape on the threads, and carefully hold the stud in a vice. You should easily be able to remove the prop nut. Then install the prop stud into the crankshaft until it stops, then back it out 2 turns.

The prop shaft/stud stays with the engine. You remove the prop nut/spinner nut just as with other conventional crankshaft engines. A double-nut installation is not necessary. Just a single prop nut or spinner nut will do.

Prop and spinner installations work as normal. Nothing unusual. If you want 'better than usual' for a spinner installation, Jett has intergral backplate spinners that actually become part of the engine (replaces the prop drive).

The prop shaft stud installs into the crankshaft, but should not be tightened or bottomed-out. You can actually back it out a bit if needed a bit longer shaft for a thicker prop/spinner backplate combination. You do want to ensure the stud is threaded into the cranshaft at least 3/8".

On the 90L the thread size is 5/16-24

There are three big benifits of the removable shaft stud

1) If the engine is crashed, you will not bend the crankshaft. The stud might bend. Replacement cost of that is about $2.00 (as opposed to replacing an entire $35 crankshaft).

2) You can replace the stud with one of a different length if needed, and it is adjustable in length to some degree.

3) You can remove both the prop stud and prop drive when installing/removing the engine from an airframe. Makes some tight installations a whole lot easier to deal with.

If I can be of any assistance, please post here, or send me a PM..... I will be happy to help.

Bob Brassell


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to Kelley)
       Post #: 2

RE: Prop Shaft Question - 12/13/2004 5:18:48 PM   
Kelley


 

Posts: 52
Joined: 4/18/2002
From: memphis, TN, USA
Status: offline 		Thank you for your response. I was confused but you have done a nice job of explaining. I have not run my new engine yet (waiting to finish the plane) but it is a great looking piece.

(in reply to bob27s)
       Post #: 3

RE: Prop Shaft Question - 12/13/2004 5:56:00 PM   
bob27s



Posts: 4637
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Glad to be of help.

What aircraft are you planning on installing it in ??

Bob


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Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to Kelley)
       Post #: 4

RE: Prop Shaft Question - 12/17/2004 5:13:14 AM   
Kelley


 

Posts: 52
Joined: 4/18/2002
From: memphis, TN, USA
Status: offline 		Here are a couple of pictures of my 90 BSE FIRE in the plane I am building. It is a Great Planes F14 that I have modified for swing wing, flaps, and full tailerons. Most of the major surgeries required for the changes I have made are done but I have changed jobs recently and that has put a major kink in my building. I haven’t done much work on it in the last two months. I hope to finish it this summer. As you can see from the pictures I plan to run the exhaust through the fuselage and then down and out the bottom of the plane just behind the retracted nose gear. I think I drove Dub nuts when I was ordering the engine because he did a lot of special things for me to make the exhaust work. I have never run a high performance engine before and I am really looking forward to seeing what this thing will do.

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(in reply to Kelley)
       Post #: 5

RE: Prop Shaft Question - 12/17/2004 3:16:33 PM   
bob27s



Posts: 4637
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Now THAT is an outstanding aircraft !!!

REAL nice! Definately something I want to follow along with.

Maybe post info for this on the Extream Speed forum. Guys there will just eat it up !

BTW... do not be concerned about running the engine. It will run just like any other sport engine. In fact better than most. Very well behaved, idles well...... transition is really nice. Do take the time to do the initial run-in on a test stand per the instructions. Helps you become familiar with the engine, and after a handful of runs you can try a few different props as well.

Thanks for the photos
Bob

< Message edited by bob27s -- 12/17/2004 3:21:14 PM >


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to Kelley)
       Post #: 6

RE: Prop Shaft Question - 12/29/2004 4:50:40 PM   
Kelley


 

Posts: 52
Joined: 4/18/2002
From: memphis, TN, USA
Status: offline 		Bob,

Is there any problem using a 5/16-24 bolt instead of the stud and nut? My engine did not come with a thrust washer so is it OK to use a standard 5/16 washer?

(in reply to bob27s)
       Post #: 7

RE: Prop Shaft Question - 12/30/2004 7:05:47 PM   
bob27s



Posts: 4637
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Dub typically does not recommend using a bolt into the crankshaft itself. The main reason is that by using the stud you ensure that you have the correct minimum thread engagement prior to installing the prop.

Also, the stud installation provides for use of a rounded prop nut, or a conventiional adapter nut and spinner. And as noted, in a crash, the stud will take the brunt of the punishment.

Having said that, I am aware of a few folks using a bolt for prop installation. No reports from any of them with difficulty. I used the bolt configuration one time myself, but that was in a helicopter - cooling fan installation.

Bob


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Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to Kelley)
       Post #: 8

RE: Prop Shaft Question - 3/5/2005 6:47:05 AM   
Kelley


 

Posts: 52
Joined: 4/18/2002
From: memphis, TN, USA
Status: offline 		Bob,

I purchased my BSE 90 FIRE from Dub last year. With the engine I had Dub make a special exhaust pipe (not a tuned pipe, just a straight pipe). The pipe consists the header with a .625” rise and a 12” length of straight .875” tubing with a 3/8” plug in the end.

After receiving the engine and exhaust I have come up with “Plan B” for the exhaust. Rather than use the 12” tubing I am going to remove the 3/8” plug and reinsert it into the header. The engine is mounted upright and the exhaust will run back through the center of the fuselage. At the end of the header I will transition to the 3/8” tubing (via the plug) which will make two sweeping 90 degree bends and come out the bottom of the plane where the tubing will hug the bottom of the fuselage all the way to the rear of the plane, where it will end. The idea is to conceal the exhaust (without the complication of trying to run the exhaust inside the fuselage all the way to the rear of the plane) to the greatest extent possible.

I have three questions for you. First, how can I get the plug out of the original length of .875 tubing without damaging it? It appears to be a press fit with some type of sealant. Second, what is the sealant (I need to use it when I reapply the plug into the header)? Third, the 3/8” plug has a .55” OD and a .355” ID. Did I get the wrong plug or am I missing something about adapting this to 3/8” tubing?

Here is a side view of the plane showing the exhaust and two updated photos showing the engine sitting in the plane.

I am about finished with the plane and am ready to start working on the engine installation. Any help would be appreciated.

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< Message edited by Kelley -- 3/5/2005 7:00:29 AM >

(in reply to Kelley)
       Post #: 9

RE: Prop Shaft Question - 3/5/2005 3:36:30 PM   
bob27s



Posts: 4637
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Hi Kelley

Looks like that project has progressed nicely. Sharp looking aircraft.

The end exhaust exit fitting in the header is shrunk fit (interference fit), and sealed with a high temp loctite 'glue'. Similar process used to assemble the jett mufflers. It is unlikely you will be able to remove it, other than by cutting it free from the header.

I do not entirely follow this...

quote:

The pipe consists the header with a .625” rise and a 12” length of straight .875” tubing with a 3/8” plug in the end. After receiving the engine and exhaust I have come up with “Plan B” for the exhaust. Rather than use the 12” tubing I am going to remove the 3/8” plug and reinsert it into the header.


It sounds like you wish to make the header shorter, and then reinstall the outlet piece ? Is that correct? If so, you would have to cut the header to the length you desire, then cut the outlet free from the scrap piece. If this is your intension, you may want to drop Dub an email directly for advise on how to best complete this process.

As for outlet and tube size. I believe it was understood you were using 3/8" flexible tubing, as commonly used for exhaust diverters/extensions. Hose/tube is defined by inside diameter. The end outlet is sized around .5" so the 3/8 material would stretch and secure properly over the outside of the exit. One of the keys here is that the exhaust system extention has to be larger in inside diameter/cross section than the exhaust exit. The .355 outlet exits into a .375 tube, which is what you want at a minimum. Plus, Dub sizes exhaust exits to obtain the correct flow and back pressure in the exhaust system.

If you were considering solid 3/8 tube, then that would be an issue. Solid tube is sized by the OD (outside diameter). In which case, you would want to use closer to .50" tubing (.062 wall gives you .38 inside dia), and couple the header to the tube with a length of silocone coupler material.

I understand where you are going with this installation. But if this were my installation, I'd simply rout the exhaust out the bottom of the plane, making that extention tube as short a possible.

If I missed something here, please let me know and I will try to help further.

Bob


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to Kelley)
       Post #: 10

RE: Prop Shaft Question - 3/5/2005 8:22:07 PM   
Kelley


 

Posts: 52
Joined: 4/18/2002
From: memphis, TN, USA
Status: offline 		Bob,

You are correct in what I am trying to do. If I end the exhaust at the bottom of the plane I will end up with residue oil all over the bottom of the plane including the main landing gear. Some oil is also bound to find its way past the gear doors and into the fuselage. As you can tell from the project, I like to try new things and I wanted to get that exhaust to the rear of the plane. I will go with .5” thin wall tubing to get the proper ID of the pipe. Is there any detrimental reason not to run the exhaust to the rear (other than weight, which I am OK with)?

Here is a better sketch of how the exhaust will run. I appreciate all your input.
[image][/image]

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(in reply to bob27s)
       Post #: 11

RE: Prop Shaft Question - 3/5/2005 9:02:54 PM   
bob27s



Posts: 4637
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		An exhaust that long will tend to create some strange backpressure tendencies. Very hard to predict though.

Try it. Nothing to lose.


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Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to Kelley)
       Post #: 12

RE: Prop Shaft Question - 4/20/2005 3:15:48 AM   
Kelley


 

Posts: 52
Joined: 4/18/2002
From: memphis, TN, USA
Status: offline 		Bob,

I want to thank you for all your advice and counsel on this exhaust thing. Here are pictures of what I am going to try. I will run the engine with and without this extended (7/8” ID) tailpipe under the fuselage and measure the RPM difference. If I get a noticeable difference I will use only the short extension that gets me out the bottom of the plane and eliminate the long run to the rear. Again, my goal here is to try something a little different and to solve the oily clean up at the end of the day.


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(in reply to bob27s)
       Post #: 13

RE: Prop Shaft Question - 4/20/2005 9:52:54 PM   
bob27s



Posts: 4637
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Hey there...

Thanks for the update.

Yep, it sure is different. Only some testing will see how it wor