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Post by racket on Apr 14, 2017 4:16:21 GMT -5
Hi Chris
Yep , things did more quickly in those early days , I use to get the Traplet Publication , RC Jet International , ~20 years ago , to read what the "professionals" were doing on the other side of the earth , whilst I experimented with my "agricultural" turbo based engine , they were interesting times , I was also a Member of GTBA but let it lapse for a decade before rejoining , but RC engines sorta reached their evolutionary end , and once the engines became commercially available the amateur experimenters slowly faded away .
The GTBA is supposedly still considering a radial inflow engine , but haven't heard much of it lately .............theres more experimentation here on JATO these days , its keeping up the best traditions of those early GTBA days .
I had a bit of a read of Kurts book and it seems he was "fixated" with having purely axial exhaust from the turb wheel when anything up to ~15 degrees of swirl is acceptable , the extra swirl from a lower blade exit angle would have kept temps down and would only have required a tad longer blade , an easy tradeoff to achieve sufficient flow area through the turb throat ...........there are small turbos with worse component efficiencies that have been made into engines .
Yep , some of the EDF engines are beautiful bits of kit , when I was looking for large horsepower electric motors for use as a starter motor for the 12/118 engine I was going around the various EDF manufacturers Sites looking at their motors , those 120 mm EDFs can certainly suck some kilowatts...............but the fans were very expensive ..........LOL, I could make a whole turbine engine for less .
Cheers John
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reedy
Veteran Member
Joined: January 2017
Posts: 111
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Post by reedy on Apr 14, 2017 6:55:21 GMT -5
Hi John
120 EDF is where i would buy a turbine, cheaper and easier than carrying 2 car batteries around and a generator and a slack of lipos for a 4 minute flight. EDF get cheaper as the go smaller but turbines get more expensive ! The hawk 100r is an interesting radial turbine heavy but wins on fuel economy to save weight. Been a biker on and off all my life but the police in the UK would take a dim view of a jet powered one,pity.
Sorry for going off your build thread Jeff,looking forward to see it going.
Chris
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Post by jetjeff on Apr 14, 2017 14:52:36 GMT -5
Hi Chris,
No worries buddy, I hope to make some decent progress on Heineken II this weekend. At least get the shaft finished, possibly start on the front cover.
Regards
Jeff
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reedy
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Joined: January 2017
Posts: 111
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Post by reedy on Apr 16, 2017 3:47:18 GMT -5
Hi Jeff Bit late but found some info on making and turning a hollow shaft it may help Adam but still looking for another write up i have on the KJ66 shaft. Still haven't got a new scanner hope pictures are OK. please note the 1mm rad on the tool,necessary but you need to check that the bearing slides up fully and seats against the shoulder and inner race,worth turning a test end and check with 0.0005 feeler also hold up to the light to check it caused me problems with the 16mm o/d bearings of the FD3 they have a very small rad i got round it by using the knife tool with the 1mm rad but when finishing did an undercut by moving in 10 thou on the shoulder area,this means when polishing with emery in the journal area to get the slide fit it made the corner clear. I tended to stop turning with 1-2 thou plus and emery to a fit. try not to use tipped tools as they put to much force ,strain and heat on the job,if you do use them to rough down keep checking the centre pressure if heat builds up then use HSS tool for the last 10 to 15 thou as you do with grinding . Keep the HSS knife tool sharp. always cover the lathe bed with kitchen paper when you emery on the lathe and the red emery is cloth is far better, never wear gloves when turning. once you have done a test piece you have a good comparator to measure with your mic. When trying your compressor gentle heat with a hair dryer (must be a very snug fit or balance will be a nightmare)to test fit always put grease on when trying as it is prone to picking up,if it does do not twist, reheat and tap the shaft through with the shaft fitting through a hole in flat plate. doing the KJ shaft i would stick the whole length out grip in 4 jaw chuck DTI the end best you can then centre drill the end and do all the turning using left and right handed tools doing both ends without removing. if using dies turn a extra shaft length with long lead in same length as die at core dia also chamfer to full thread diameter and use a die holder that fits in tailstock, use split dies as the thread is best cut large to minimize any slack in the nut. Best to have the ally spinner with the tapped hole to check the thread fit ,leave the spinner o/d till you have done the shaft. reset the shaft in 4 jaw chuck the spinner o/d to be done on the shaft with an old bearing and compressor wheel fitted,hard to decide about when to do the tommy bar hole as you need it to undo the spinner after turning.i did it after turning I made a mild steel tool that fitted in the tailstock chuck that the finished o/d spinner fitted into and had the hole drilled through then used a hand drill and a cut down drill with the plain shank to guide it,will try to find it and take a picture. hope it helps bit late for you Jeff, did not realize he silver soldered the end on. Chris p.s please anybody chime in with other tips or ways of doing it as I know there is more than one way to skin a cat!
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Post by jetjeff on Apr 16, 2017 9:56:02 GMT -5
Hi Chris,
My Kamps build has a hollow shaft too. I originally was going to have the spigots tack welded, but I thought the heat would distort the shaft. So I just install a roll pin through each spigot. I don't think they will come out.
Seems to me the shafts should be heat treated and precision ground, but hey, we have only a limited amount of machines to work with.
Regards
Jeff
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reedy
Veteran Member
Joined: January 2017
Posts: 111
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Post by reedy on Apr 16, 2017 13:15:47 GMT -5
Hi Jeff If you use a 12.9 caphead bolt the heat treatment is already done,GTBA did not recommended diy heat treatment . I think it would distort with welding we use to make are own 6.8 mm extension drills for then reaming 7mm and had a dozen brazed by maintenance throw them in the scrap bin,after that I just loctited them as long as everything was degreased they worked great,no good for a gas turbine with the heat. if you notice any problems with the ends you could try shrinking them in, www.youtube.com/watch?v=c-ZEJ3KLLeQThey used this method for large cutters at work,never took any notice of it! they had these shrink m/c near ever m/c cell. Maybe try the tube shaft part in a collet in the lathe and the end shafts in the tailstock, blowlamp to heat the tube with lathe on slow,switch blowlamp off, stop lathe and push in with tailstock. if you look at the colour change looks like temper colour blue purple 280-300c you would need to see how much the tube expands to know how big to make the ends. still don't know if i would pin it as well! belt and braces but the pin will not transmit much force it is a bit like the shear pin fitted on the leadscrew of the lathe . Chris
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reedy
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Joined: January 2017
Posts: 111
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Post by reedy on Apr 22, 2017 14:59:13 GMT -5
Hi Jeff youtube vid on coatings and gluing by Dan Gelbart. worth watching the whole series. www.youtube.com/watch?v=x7onZGqrYyYChris PS corrected temp on last post mixed up in F-C
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Post by jetjeff on Apr 24, 2017 3:28:50 GMT -5
Hi All, I finished the shaft, however, it's off by .005" when checked with V blocks and a dial indicator. I'll have to make another one. Regards Jeff
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reedy
Veteran Member
Joined: January 2017
Posts: 111
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Post by reedy on Apr 24, 2017 5:27:42 GMT -5
Hi Jeff Read the PT35 construction manual page 6 on making hollow shafts you will not build one perfect ,there will always be some vibration,have a go at balancing it using the method in the manual and blue tac,only grind away when you are sure your balancing method is working and then only at each end of the shaft. I was a toolmaker for 40 years and never got anything perfect, you need to give yourself a tolerance.
leave perfection for people that never finish anything.
Chris
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Post by racket on Apr 24, 2017 17:31:09 GMT -5
Hi Chris ............."leave perfection for people that never finish anything." ................never a truer word Cheers John
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reedy
Veteran Member
Joined: January 2017
Posts: 111
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Post by reedy on Apr 25, 2017 13:20:50 GMT -5
Hi Jeff Sorry was speed reading 5 thou is too much but still worth trying to balance it, another learning curve. May be try the heat shrink method,make sure to turn the end features all in one go using left and right hand lathe tools.
Chris
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Post by jetjeff on May 21, 2017 6:10:36 GMT -5
Hi All, I completed the 2nd shaft. Regards Jeff
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Post by jetjeff on Nov 2, 2017 0:29:04 GMT -5
Hi All, Whew, my 'other' build thread was way down on the DIY list, but thats a good thing, lots of other folks building stuff. Anyhow, I thinned the blades for my Heineken part II turbine even further. Here is a comparison with the 2nd wheel I made for my Kamps build. As you can see the blade angle is quite a bit less on the Kamps wheel (probably closer to 30 degrees vs the Schreckling wheel at 37). Regards Jeff
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bournaVee
Junior Member
Joined: January 2017
Posts: 66
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Post by bournaVee on Nov 3, 2017 17:10:03 GMT -5
Hi jeff, Do you think you can make your turbine work for up to 10hours? Is it possible?
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Post by jetjeff on Nov 4, 2017 8:53:08 GMT -5
Hi bournaVee,
I'm trying to get them to run at all first,,,LOL.
Hmmm,,,the closest engine size wise, that I have fuel consumption values for is the AMT Olympus. That engine consumes 800 ml per minute. So, I guess the calculation for 10 hours would be 800 x 60 X 10. 480000 ml? Somebody can check my math but that's a lot of fuel.
The AMT Olympus has a compressor diameter of 84 mm along with a turbine diameter of 84 mm.
I guess the other 'variable' would be would the bearings last 10 hours.
Regards
Jeff
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