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Onan Generators

Onan 7.5 JB's Recovery Towards A New Life


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  #291  
Old 02-18-2017, 04:38:55 PM
JohnnyC JohnnyC is online now
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Default Re: Onan 7.5 JB's Recovery Towards A New Life

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Originally Posted by Leon N. View Post
I used 1/4 inch hardware cloth on my JB Magneciter and engine hot air discharges with no apparent problems. I Also stuffed a piece of aluminum screening into that opening in the control box. After removing an electrocuted mouse from one spark plug and a nest in the flywheel cooling air shroud I built a mouse condo outside the generator shed. No more mouse problems now going on many many years.
I wonder why Onan did not engineer anti-mouse guards into their design. There are thousands among thousands of J series plants out there that were/are mouse infested which could have been easily prevented. Below is a snapshot of the screening I installed in one of the vent guards. I did the complete bell end today. I will deal with the control box at a later time.

JohnnyC
New Jersey
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  #292  
Old 02-18-2017, 04:41:39 PM
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Default Re: Onan 7.5 JB's Recovery Towards A New Life

3:30 pm Saturday Afternoon Update

I got all the parts primed and now goofing off for the next hour. Below is a small sample of what got primed and waiting for paint.

So far I covered the following from my earlier bullet list:

0) Preparing for the day - make a pot of coffee, make breakfast
1) finish installed the anti-mouse screen into the bell end tin
2) make a pot of coffee
3) final cleanup of many parts previously stripped of old paint
4) Clean up the workshop paint area to provide a dust free environment for painting
5) make a pot of coffee
6) Hang the parts in the workshop in a manner where I won't accidently bump into them as I prime and paint.
7) make a pot of coffee
8) Prime then wait 1 to 2 hours
9) make a pot of coffee
10) Goof off
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  #293  
Old 02-18-2017, 05:18:30 PM
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Default Re: Onan 7.5 JB's Recovery Towards A New Life

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Originally Posted by len k View Post
To hold the screen cut up ~ 5-6 sections of sheet metal tabs about 1 x 1/2 inch, tack or pop rivet them on end cover. Install screen and fold over tabs. I say 5-6 so it will work even if 1 or 2 break in future.

Screen appears to be ~ 95% open, would be interested in knowing where 60% reduction comes from. It's forced convection ( fan).
Screens of varying free hole areas (FHA) were tested and a regression analysis of the results was performed to produce a mathematical relation for screen pressure as a function of velocity and FHA.
The resulting relation was: A V P 59 .2 50.1 108.42 × = Where P is the screen pressure, V is the velocity and A is the FHA. This gives a power law dependence with velocity, and an inverse power law dependence with FHA. As expected the screen pressure increases with velocity, and decreases with increasing FHA. These results were as expected since with increased velocity comes increased drag, while a greater FHA gives a greater open area and impedes the flow less. This result does not take into account boundary conditions at FHA of 0% and 100% and is ideally only valid between 30 – 55 % FHA but can probably be extended 10% in either direction with reasonable confidence.
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  #294  
Old 02-18-2017, 05:35:56 PM
len k len k is offline
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Default Re: Onan 7.5 JB's Recovery Towards A New Life

I'ld like to look at the source to see more.
Could you post a link to where your quoting from please?

Looks like the 3 numerical values might be coming from table somewhere.
.

Last edited by len k; 02-18-2017 at 09:55:39 PM.
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Old 02-18-2017, 06:11:03 PM
JohnnyC JohnnyC is online now
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Default Re: Onan 7.5 JB's Recovery Towards A New Life

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Originally Posted by len k View Post
I'ld like to look at the source to see more.
Could you post a link to where your quoting from please?

Looks like the 3 numerical values might be coming from table.
.
Len, I think the mathematical equation for computing what you are looking for can be seen in the picture below. Let me know if you have trouble figuring it out, but it is basic Math 101.

JohnnyC
New Jersey
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Old 02-18-2017, 06:23:12 PM
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Default Re: Onan 7.5 JB's Recovery Towards A New Life

Saturday Late afternoon Update

I had a wonderful day long Onan therapy session to rid all my stress otherwise I may go crazy. I accomplished all the tasks that I planned earlier today which was previously posted. I attached 4 pictures of a few things that were painted, but obviously I could not get everything into 4 pictures. For now, I am cleaning up and going to relax for the evening. The workshop doors are closed and locked to avoid anyone from entering accidently causing any damages. I may go out into the workshop later this evening, but maybe it is best to return tomorrow morning.

JohnnyC
New Jersey
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  #297  
Old 02-18-2017, 07:07:41 PM
Vanman Vanman is offline
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Default Re: Onan 7.5 JB's Recovery Towards A New Life

Is it important that the temperature be maintained above a certain minimum while the paint is curing, or only while you're shooting it?
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  #298  
Old 02-18-2017, 07:53:37 PM
JohnnyC JohnnyC is online now
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Default Re: Onan 7.5 JB's Recovery Towards A New Life

I try to maintain a temperature between 60 and 80F while shooting. I will preheat the room if needed to ensure the parts are to temperature too. When done I may keep the heat on for several hours if the temperatures are less than 50 degrees outside, otherwise I'd kill the heat if it is being used. Today, temperatures were in the upper 50's and I used no heat at all today. tomorrow forecasted temps will be in the low to mid 60's with low humidity - perfect for painting on my opinion.

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New Jersey
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  #299  
Old 02-18-2017, 07:55:50 PM
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Default Re: Onan 7.5 JB's Recovery Towards A New Life

WOW!
Great job
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Old 02-18-2017, 10:10:22 PM
len k len k is offline
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Default Re: Onan 7.5 JB's Recovery Towards A New Life

Johnny ..... great paint job. You do good work.

Math...... I don't quite recognize your math, let me guess 3 dimensional stress for torsion of a rectangular bar?

I turned the crank for 32 pages, it may simplify to equation 79 and 80
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Last edited by len k; 02-18-2017 at 10:22:55 PM.
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