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Post by madpatty on Jun 23, 2014 11:34:43 GMT -5
Hi Racket,
Today i managed to somehow remove the balls out of a riveted cage SKF ball bearing....was a royal pain in the ass..
How to convert that bearing into a all ball no cage(complement arrangement).....i have ordered some ceramic balls of same size as steel balls....
Thanks, Patty
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Post by madpatty on Jun 22, 2014 23:48:32 GMT -5
Hi John,
Can you suggest me a suitable axial turbine wheel for compressor with:- Inducer- 71mm Exducer-105mm
According to calculations it is to flow 60lbs/min.
Tried searching on net but didn't got suitable results. In the kamps book i had that page mis printed where general calculations are available...
You may also provide any general formula for the turbine wheel diameter wrt the compressor diameter.....
Thanks, Patty
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Post by madpatty on Jun 22, 2014 21:25:54 GMT -5
Thanks Racket, That was exactly what i was thinking....
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Post by madpatty on Jun 22, 2014 4:25:54 GMT -5
Preload was on the "base" of the cup towards the centre , the outer portion of the base was used to set the "endfloat" in the cup pocket in the bearing housing .
How towards the centre?? Weren't the spring pushing both the cups outwards towards compressor and turbine??
"Endfloat" can you elaborate please?
Thanks, Patty
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Post by madpatty on Jun 22, 2014 3:17:44 GMT -5
Hi Racket,
Needed some details on the bronze cup arrangement you used in one of your engines..... How did you preload the bearings and what bearings you used? (if i am not wrong the spring was between the cups touching their OD and pushing the bronze cups against each other) What changes you went for in your skuld 666 engine regarding te preloading..
Do the pair of hybrid angular contact bearings on each end of the shaft also need any spring pre load??
Thanks Patty
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Post by madpatty on Jun 19, 2014 23:02:05 GMT -5
Hi Patty Mill size .............as big as possible , my mill is now too small :-( Cheers John Thanks John, For the "Optimistic Approach!!!". Cheers, Madpatty
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Post by madpatty on Jun 19, 2014 22:25:20 GMT -5
Hi John, Thanks for the technique....i used that technique once for making a cam from a cylindrical shaft....
I am thinking of buying a Milling Machine for my workshop....work will be fabricating small parts for engine... "Main driving force was lack of milling for that compressor DIffuser plate."
Can you suggest what size mill will do the job.....any specific product suggestions are also welcome...
Thanks, Patty
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Post by madpatty on Jun 19, 2014 9:19:21 GMT -5
Just a mini update...
Journal bearing assembly almost done....will post some pics shortly...
Now will be fabricating the oil inlets for the bearings...that will two small holes drilled just above the two bearings reaching exactly the midpoints on the periphery of the journals from which pressurised oil will be fed to bearings.
I am facing the problem of making that oil sump inside the shaft tunnel (idea courtesy- Ander's build) for collecting the oil from the bearings at the oil outlet due lack of milling option...
Can there be some other possible way of doing that??
Cheers, Patty
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Post by madpatty on Jun 18, 2014 20:29:19 GMT -5
Hi Miuge,
Sorry to hear about the problems...
Till the time you are experimenting with all those starts and stops one after the other i suggest you use a bit high power and high pressure pump for lubrication purpose until you are thoroughly aware of the oil pressure variation during the entire engine run....
I myself wrecked several turbo shafts during my initial turbojet runs until i replaced my lube pump with a large hydraulic(though we don't need such high pressures, i am using a pressure relief valve with it) pump....
Still without the oil cooler the pressure used to reduce to mere 40 psi(starting from 100 psi) just after 5-10 mins of run until i increased the flow of oil through bearings again...
MOREOVER using thicker oil sometimes exagerates the problem related to startup if oil pressure is not dynamically controlled resulting in a hot start...
So many things to be taken care of!!
Cheers, Patty
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Post by madpatty on Jun 18, 2014 9:28:05 GMT -5
Hey Patty. Thanks and great to hear your doing a similar project. Bearings are just angular contact, steel case and ceramic balls. GRW make a quality bearing and can be found all over the place. wheels have been turning slowly lately but all ways working on something. Got a spot welder in the making right now for combustion chamber and have had a try at metal spinning with mixed results. Will do an update soon. Plenty of parts made. Cheers Beaker Hey Beaker thats cool all that stuff going on... Cheers, Patty
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Post by madpatty on Jun 17, 2014 20:02:08 GMT -5
Thanks John,
I was also thinking of rejecting that idea...off the shelf bearings cant handle those extreme conditions.
I will try the present design first....anything i can do to elongate the standard shaft a bit of i have missed some technique of doing that on the forum.??
I think a bit long cc would be good to start with....
Or i try fabricating a whole new shaft with standard compressor and axial turbine and run it on standard bushes...??
Your thoughts.
Thanks, Patty
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Post by madpatty on Jun 17, 2014 17:31:46 GMT -5
Thanks John,
In my present engine build The size between the brass bushes is just about 40-45mm and so the main portion of combustion chamber will be at most 60mm(approx)..... Is it ok for such a small comstion chamber??
If at all i will use ball bearings then it will be a whole new setup incorpoating axial turbine wheel(designs taken from GR130 and GR180 etc).....in that case also normal ball bearings won't go??
Cheers, Patty
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Post by madpatty on Jun 17, 2014 10:38:49 GMT -5
Hi Beaker,
Been using your thread as one of my references in building one such engine...
Cool work you are doing...
Had a few queries regarding your engine.
What type of ball bearings are you using for your build?? Are they simple ones,angular contact or hybrid bearings??
Cheers, Patty
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Post by madpatty on Jun 17, 2014 5:22:06 GMT -5
Hi John,
Can the normal steel ball bearings be used as the rotating elements at such high rpm's....at the place of brass bushes?
Or there is some special arrangement to use them?
Thanks. Patty
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Post by madpatty on Jun 16, 2014 20:05:43 GMT -5
Hi John,
Done a few calculations:-
Hx35 flows 40lbs/min at 123000 rpm at 75% efficiency and a pressure ratio of 3.0
Tip speed- 534.27 m/s Air Outlet temperature- 98 degree celsius Density of air at compressor exit- 1.6477 kg/m3 Radial velocity- 139 m/s Supply value- 0.261 Blade angle- 65 degrees(approx) Overall speed vector- 469.45 m/s
Therefore outflow angle- 16.49 degrees
Now all this i have calculated....
How to calculate the throat area for maximum mass flow...
I wasn't able to find that section in the book..
Thanks, Patty
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