reedy
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Post by reedy on Apr 21, 2017 11:59:22 GMT -5
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reedy
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Posts: 111
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Post by reedy on Apr 21, 2017 11:16:59 GMT -5
Hi Adam Another good youtube vid on spot welding,mother of all diy spot welders! more like a prototype.some really good tips and tricks. I am going to check out is other vids. www.youtube.com/watch?v=82Iil0fFN9YChris
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reedy
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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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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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reedy
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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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reedy
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Post by reedy on Apr 14, 2017 2:36:21 GMT -5
Hi John I built 4 Fd3 engines still have the original one but it's like a old broom the back NGV was cut off fitted with another, the diffusser was unriveted angle changed to 23 degrees with curved blades this change was because I increased the o/d of the compressor wheel to 68mm and m/c it from aluminium with no top cover to the wheel replaced with a nylon cover close fitting this was following geoff Vaizy PT35 design who went through the math in the GTBA newsletter think he even did a simple program,not sure now so long ago.
Kurt set the design temp at 650c and with early combuster design you had hot spots of 750-800c which just distorted the whole back end so people increased the turbine clearance then it was a vicious circle . I tried to keep the temp at 550- 600c
The combustor was changed about 2-3 times never did the original vaporizer coil combustor it puffed like a steam train at low rev,s think the engine had problems with too much percentage air to cool the turbine wheel disc. There is a gap to the bearing tube which I did not do as it allowed the turbine to move and catch the NGV housing stopping the control of the turbine gap which i closed up as tight as possible,about 5-6 thou.
I changed the oil system to oil in fuel system feed to the front of the front bearing all cooling air for the bearing flows through the front from the diffusser area and the hole in the middle of the tube was closed off as the combustor does tend to drop carbon soot and can contaminate the bearings.
So a FD3 not really as Kurt designed but follows standard practice as with Kamps and KJ66. things moved quickly early on and I moved from the FD3 to Kamps then KJ66 gave up after this as £120 for a pair of bearings ,NGV £150 , ECU £250 ? to be able to rev to 115k a cast turbine wheel £150 got too much to risk flying and the models ended up big with the power and fuel weight.
Almost finished built a mw54 but gave up due to cost and still to big a model to lug around,lambert Kolibri turbine would be nice but silly cost, I also lost use of a old airfield with tarmac runway.
makes me smile now as gone to 90mm EDF and get more thrust than my FD3 also get the same sound with the multi bladed fans,but miss that aroma as you do a fast fly past !
Still think the FD3 is a good engine to make,you will always be able to get the bits as you make everything apart from the bearings,can be made for £100 with all start equipment,you learn a lot about how gas turbines work but not my first choice for flying a r/c aircraft.
Chris
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reedy
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Post by reedy on Apr 13, 2017 6:00:47 GMT -5
Hi John
Home made axial wheels are not the best thing bit of a black art ,you guy's use radial wheels professionally designed and made wheels out of the correct material, the GTBA where looking into designing a model engine to use radial wheels don't think it happened, when I made a KJ66 using a car compressor and a Cast wheel and it just worked no messing. The FD3 is very low pressure makes the combuster struggle to work as Kurt say's in his book at 40 degrees turbine blade angle it goes into melt down,he was trying to get the most out of it he could with building it very light 0.9kg and low rev,s 75k ,it's a lot easier when you can build thicker material and stronger. People try to treat the FD3 as a car turbo compressor wheel and it's not the same, interesting and challenging and unique with that compressor wheel.
Chris
P.s the FD3 almost drove me nuts built the Kamps and KJ both worked well and then I went back to the FD3, Don't like to be beaten, the twisted wheel is hard to get right but succeeded in flying it. early on I did fly one with the wooden compressor wheel and twisted blade turbine wheel but only low 4.5lb thrust finished up at about 6.5 lb with ally wheel at 85k easier if you m/c the turbine wheel from solid gives you better root profile but that takes you into shaft problems with the weight the FD3 has a very long shaft, really a blind alley for Kurt who started again with the KJ design but he did fly a heli FD3 powered in the 90s using shaft power at the suction side, saw it at a GTBA lecture somebody said why did you not use the hot end as twice the power his reply was you do it ! following year he turned up with a turbo prop driven from the hot end.check my vids on youtube under reedy
have you ever looked at the math of the FD3 Kurt does do unusual and interesting designs, he does a twin shaft turbo prop and fan design with one shaft running though another and the Tk50 50mm wheels in a bigger 95mm can for efficiency.
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reedy
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Post by reedy on Apr 13, 2017 5:05:37 GMT -5
Hi Jeff drawn a line touching blade leading edge then another line on the back face as he grinds the concave face I get 32.5 interesting, about the same as mine never done that before. Tried it again with a line more on top 4 blades 35 degree not a good thing to do unless the wheel is vertical.
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reedy
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Post by reedy on Apr 13, 2017 3:05:25 GMT -5
Hi Jeff
Quick Quote
Insanity: doing the same thing over and over again and expecting different results. Albert Einstein
Keep smiling it's only a hobby until you retire !
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reedy
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Post by reedy on Apr 13, 2017 2:35:01 GMT -5
Hi Jeff
It does look more on the centre blade? nobody got the FD3 to run cool with the stated angles,try it and see if you still have heat problems at least you have a quick fix but if your NGV is at 38 with gaps and the turbine is 37 you will have heat problems,the first one I made had an error of 2 degrees in the NGV and even backing the turbine angle down could not get it to run cool until I remade the NGV at 36 degrees.
Chris
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reedy
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Post by reedy on Apr 12, 2017 15:25:03 GMT -5
Hi Jeff
I can open up the picture on my laptop now,only been able to view them on my Mobil,anyway can see your turbine wheel,looks like tip angle is 45 degree,I know you twisted it right just looks a lot compared to mine,i only ground the underchambered side and lightly file the curved side to thin and taper the trailing edge .with that angle it will run hot, shape looks good and you can always adjust after test run.
Chris
P.s how long did it take to polish it! you've got more patience than me.
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reedy
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Post by reedy on Apr 12, 2017 4:09:14 GMT -5
Hi Jeff You will have to bite the bullet and take it apart best way you can,every bearing should be an easy push fit at the most,if the front ends up a bit slack you can always try fitting a o ring but on first running i would not worry about the fits until you have it running right.
One of the main things about a diy engine is it must come apart easy. Better to use normal bearings for setting up and low speed testing also helps to clean everything out with the total loss oil system.
Chris
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reedy
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Post by reedy on Apr 9, 2017 16:57:19 GMT -5
Hi jeff
Normal way to take kj66 Kamps apart is to undo compressor nut take compressor off then pull out turbine wheel and shaft from rear ? I would not use loctite on compressor nut as compressor should be free to tighten it if it starts to turn.
I realize the compressor nut is integral with the compressor wheel which is the same as the FD3 turbine wheel this can give problems as if the ally wheel picks up on shaft, it makes it worse turning the whole compressor to take off, that's the reason i said put copper eze or grease when fitting.
Chris
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reedy
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Post by reedy on Apr 9, 2017 12:34:34 GMT -5
Hi Jeff
If you check the see through with the back shank of a drill what size would fit held parallel to axis's of engine ?
Are the GRW bearings cageless angular contact and are you using wave washers or a normal spring as in the kamps book ?
Chris
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reedy
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Post by reedy on Apr 7, 2017 15:44:16 GMT -5
HI JEFF if you are 5 to 9 thou you are only 2 thou off centre,just knock the tight spots off the housing,they always move on the first few runs but once cleared will settle down.
the problem with a twisted wheel is it's the opposite to what it should be which is greater angle at the root than the tip,if you stick at 30 makes it worse ,better to over twist and untwist a bit,that's another reason you need more blades as a narrower blade is better to twist.
Saying all above i don't think it's the whole problem with your Kamps engine,compressor is not doing anything you can almost see where you are blowing compressed air though straight out the back.
have you any direct see through of the NGV ?
Have you got rear preload,if so how far can you push the turbine wheel forward,use a dti on the wheel as you push,does not want to be more than 6 thou.
Did it jam up ? bit dark to see if it did ,did it free up as soon as you turned the gas off and it cooled ? if it did clearance is nearly right.
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