reedy
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Post by reedy on Jan 19, 2017 9:32:21 GMT -5
It's worth making a spot welder out of an old microwave transformer, just google how to mod the tranformer. The main arms are 5/8 dia or bigger copper bar the smaller electrodes are 1/4 copper these can be changed to any shape. the white block can be nylon or ptfe mill a groove to form a hinge, the bottom of the white block is bolted on. The top of the white block has an ally bar drilled off centre to work as a cam move the lever to clamp. The arms are just pinned in the white block with a 1/8 rods, works a a treat to weld the combustor. You need a timer that can be set to 0 to 3 sec's red button starts the spot weld.
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Post by jetjeff on Jan 19, 2017 17:36:53 GMT -5
Hi Chris,
Thanks. Heineken build 1 did have U shaped evaporator tubes, like the ones you've shown.
Did you have a pressure gauge on your builds? If so, what was the case pressure of your Schreckling turbines? Since I didn't have a Tach on mine, I'm not sure what RPM 3 lbs of case pressure equalled to RPM.
Regards
Jeff
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reedy
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Post by reedy on Jan 19, 2017 20:29:01 GMT -5
Hi Jeff
I did fit a RPM gauge on mine early on with the wooden wheel the GTBA did a electronic circuit ,i painted the top cover of the wheel half black half white then fitted a sensor in the spun ally front cover that sent out infrared and received back the reflection,think it's shown on one of my youtube videos the gauge is just a volt meter,i well try to find the info. You can buy a tacho for r/c aircraft, set it on 2 blades paint spinner half black half white and just double the reading ,think Kurt just put a blob of paint on the inner rim of the wheel,.
Turnigy Multi-Blade Micro Tachometer £11 in the Uk goes up to 99999rpm you can paint two marks even better, did not think they went up that high.use a battery touch to light the marks up don't have any fluorescent tubes on or it will pick mains cycle up.
Been looking back at your old build some nice carbon work there ,but noticed you holding the carbon base disc with the slots in, does not look right? I will have to get back to you on that.
Noticed your Dubro balancer ,make a magnetic balancer, you will be impressed how much better it is ,you may need to double up the magnets with the extra weight ,mine are 10x5 mm magnets
My pressure and rpm's won't correlate to your engine being bigger ,there is a chart in the book,if you have to buy a pressure gauge try to get one that just goes up to 15 psi for testing and as big as you can , got mine off ebay 4 inch dia , think it was something to do with a forklift trucks. has a red mark at 7 psi
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reedy
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Post by reedy on Jan 19, 2017 20:34:21 GMT -5
Jeff forgot one last point did you say you used 1.4 scale ,rpm will be a lot lower 50 to 55k ?
Your kamps engine looks nice don,t know why that's not working is that standard size
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Post by jetjeff on Jan 19, 2017 22:33:30 GMT -5
Hi Chris,
The Kamps engine is not standard size, it uses a turbocharger wheel from a Ford 7.3 Powerstroke diesel. It may just be at "the hump" requiring more fuel to get it idling.
Yes, 40% enlargement, and agree on the 50-55k redline.
Regards
Jeff
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reedy
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Post by reedy on Jan 20, 2017 4:59:51 GMT -5
Hi Jeff I feel like I am butting in to you build thread if you have had enough just tell me to stop. found a drawing for the alloy compressor, Rob Wardale has altered the design to be done on a simple rotary table, If anybody has a cnc m/c stick to Kurts drawing which has the 10 mm rad on the blades near the centre
I need to clarify a few points.
DO NOT M/C THE 22 X 1 COUNTER BORE ON THE WHEEL FACE, IT WILL FAIL !
7.5 Tip height is max size anywhere between 7.2 - 7.5 is Ok
it's more or less a copy of the wooden wheel ,I reamed the hole 5/16 inch (7.937 mm) it means you can polish the shaft to get a really good tight fit and leave the area for the bearings a slide fit ,I also incorporated the steel bush into the base design.
I left the back base of the wheel one thickness (flat) untill I had m/c the blades,but finish m/c the curve and 22.5 angled bore on the top before m/cing the blades.
I made the spinner aprox 25.0 mm dia at the base, make the 1.0 edge to 0.1 mm you will need to work it out and see how deep you can go with the 5/16 counter bore maybe 1.5 - 2 mm deep. Finish m/c the back by chucking a piece of bar in the lathe to 25 mm dia then stepped to 5/16 dia(7.937) leave it longer than the wheel thickness say 4 mm sticking out. ,drill and tap 5 mm to hold the wheel on, you need a thick washer 5/16 bore 5 mm thick with another washer on top . when you finally do the 10 by 1.5 step to replicate the steel bush on the back face use the inner race of a bearing.I left a flat area 22 mm dia by 3 mm (this area is tapered on the steel bush) in case I need to chuck it again,then I tapered out the back of the wheel to 1.5 mm thick at the edge.This is to lighten and reduce the stress on the wheel centre
hope this makes sense, if you can think of a better way ignore above,I am used to writing night notes and don't what job scrapping !
X 1.4 for you Jeff maybe do the carbon slots the same as above, yours looked like they are too close together at the centre ? hope you can read the drawing as my security software will not let me open them big ,have trouble looking at you early build pictures .
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Post by jetjeff on Jan 20, 2017 5:17:23 GMT -5
Hi Chris,
No problem with butting in my build thread,,,lol. The main problem I'm having regarding the exit blade angles on the Schreckling wheel is the blades are curved, so determining the exit angle is tough. I may just take his plans into work and see if I can make a 40% larger copy of them. The blade slots do seem close together at the center.
There were lots of mods to the original Schreckling turbine and you seem to have many of the updates. Another question I have is which way the U shapes evaporator tubes should point? My Heineken 1 build had them exiting to the right (as viewed from the front of the burner can), seems to me you'd want them exiting to the left (the same direction as the flow from the compressor).
Regards
Jeff
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reedy
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Post by reedy on Jan 20, 2017 12:19:13 GMT -5
Hi Jeff
I've Just googled Ford 7.3 Powerstroke diesel compressor wheel ,now see where you got the idea of tilting the blades but that is almost like a axial wheel all the way down to the base, other car wheels are 90 at the base then bend over to axial ,the FD3 is more like a radial water pump or stationary fan design,all the FD3 designs that where commercialized goldenwest, hobbyjet 631,PT35 are 90 to the base,the blades do not go to the centre so would not help the airflow into inlet (anybody know better shout up ) Don't mix up FD3 design with KJ66 or kamps. The Kamps and KJ66 can have bits interchanged they have similar air flow and angles 30 for the NGV ,21 for the Diffuser .
You can put the NGV kamps design on the FD3 but you will need to change the angle from 30 to 37 (or 36 on mine)
My KJ 66 has the KJ66 diffuser design , the NGV is Kamps design . the combuster is KJ66
My Kamps has the Kamps bladed diffuser design, the Kamps NGV , but has the KJ66 combustor all work well
The Kamps NGV is easier to make unless you get the Kj66 laser cut in the flat then roll.
I fabricated the KJ66 diffuser ,hard work ,if i did it again I would put the Kamps bladed design in, did not have a milling machine.
All my FD3 engine have combustors designs for that type of engine, I have the hobbyjet 631 and PT35 designs,I think the golden west used the original FD3 design, never built that combustor everybody said it was a pain,always coking up the coil.
All FD3 Type engines had diffusers that where bladed slight change of angle from 24 FD3 to 23 on the PT35 which uses the same wheel design.
The hobbyjet 631 was 22( later recommended 19) I think but he changed the wheel angle slightly.
NGV on the FD3 is 38 as per book but I have a letter from Kurt recommending reducing it to 37 (I reduced mine to 36), this is with the twisted turbine.
NGV on the PT35 is 38 which has a cast wheel which looks about 44 at root and 28 at the tip, 34 mean(later said to increase angle at tip to increase power)
All very confusing but I've tried angles from 24 straight blade to 19 curve on the FD3/64 with the hobbyjet compresser all started fine only at very high revs 90 - 95(don,t rev a twisted turbine this much mine was cast) you notice slight power increase, So go for about 23 curved but if you have 24 straight blades they will work fine. If you have too much angle on the NGV of the FD3 +37( Kurt say's but to reduce to 37 mine is 36 ) you get temp problems but can be solved by reducing turbine angle at the tip.
Hope that helps more than confuses everybody.
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Post by jetjeff on Jan 20, 2017 16:13:04 GMT -5
Hi Chris,
What is the entry NGV blade angle on the Schreckling turbine? The plans show the slot drawn on the outer cone, so it's hard to determine the entry angle.
Regards
Jeff
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reedy
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Post by reedy on Jan 20, 2017 17:53:28 GMT -5
Hi Jeff The entry angle is parallel to the shaft, exit angle is 37 degrees on the FD3/64
I am a practical guy I don't do any math on gas turbines,just bought the books and built them,but you start to understand the design and what makes one more efficient than another. but I had constraints,no miller, no rotary table, old worn lathe,small brain which is now an older small brain ! My friend did templet,s in clear plastic that you can print on ,when making the FD3 diffuser ring I just stuck the templet on and band sawed the blade slots. if I drilled a hole I did it as accurate as possible then used one part to drill through for the next. when making the wheel I did the same using paper templates ,the covered wooden wheel is more efficient than the ally one but the ally one is stronger and more stable,to use the ally wheel I made sure the gap loses where as low as I could ,very small gap to inlet cover plate.then reduced the angle of the turbine wheel and twisted ,curved the tips more ,makes it cooler you send more power to turning the compressor wheel but reduce thrust runs cooler but I can rev it more to get the power back ,on the standard FD3 with the alloy wheel I take it to 7.5 psi. The kj66 is the most efficient design. the NGV blades are narrow like a glider wing. there is no overlap of the blades, over lap causes interference drag like between the wings on a biplane.when making the kamps try to reduce the width at the inner root.
The wedge diffuser on the KJ66 helps to hide the screws and pipework not sure if it,s the best design now,it does not help the airflow go round the bend. when making a bladed diffuser try to reduce the drag from the screws,I turned the thread off in that area and sharpened the leading edge,it may be better to make some of the blades a bit thicker were a bolt or pipe goes.
The combustor has straight sticks from the rear, I think this helps as the air is hotter at the rear going down the tubes helps to vaporize the paraffin and the fuel cannot pool in the stick.The area at the front were the sticks end there are nozzles to spin the burning fuel and air with no sticks it spins the air ,fuel easier and the hole pattern helps to trap it there longer. but you can end up spraying fuel straight down the stick un vaporized, the fuel needle must touch the inside of the tube to smear fuel down the tube.
With your x1.4 FD3 you have added hooked tubes ,the combustor was not designed for these tubes, you will have added extra air in the primary zone ,it may tend to blow the flame out or burn later,I don,t know how the hole pattern will work x1.4 . You may have more problems when you run in on paraffin,you can try restricting the air flow down the sticks ,fitting a tube(or crimp it with a tool as in my youtube video) inside the sticks at the inlet and as hobbyjet 631 combuster fitting a stainless spring made out of 316 mig welding wire ,anneal it by passing through blowlamp flame then use a battery drill twist round on a rod make about 1 inch long drill small hole in end of stick push spring in then thread last bit through hole to stop it coming out. that should delay the fuel in the tube and break up any droplets.you may need to try blocking,reducing some holes at the front using stainless screws and nuts ,just peen the end of the thread slightly to stop the falling out.
My Hobbyjets 631 walking sticks work will but the combustor design does not swirl it round but goes in a dough nut shape, don't seem to have any starting problems, the flame is locked right at the front, the inner rad gets very hot The colour of the sticks should be biscuit colour like a spark plug.it can get black at the very front face as it breaks down the fuel and burns (think they say it goes through a cracking process) when at idle the inner flame colour will tell you how it's burning it should be blue ,yellow lack of air at the front .you can only do this if the turbine blades and ngv blades are not glowing red or orange. it is amazing how you can see right to the front you will be able to see the sticks glowing yellow.(another reason to not have to much blade overlap)
That's it for tonight 5 hrs ahead of you 11 pm now .
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Post by jetjeff on Jan 21, 2017 4:41:29 GMT -5
Hi Chris, Thanks for the info. Here is a pic of the NGV being trued up for concentricity and blade tip clearance, which is about .009-.010". I wish I had the I.D. grinder my dad had at his machine shop,,,lol. Regards Jeff
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reedy
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Post by reedy on Jan 21, 2017 4:42:14 GMT -5
Hi Jeff You made me check Kurts FD3 book on the NGV have corrected some of my Posts on NGV angle. it is too much at 38(shows 52 in book 52+38=90 I am just giving the figure from other 90 angle) If you have made it 38 don't panic or remake just reduce angle on turbine wheel by 1 more degree. The drawing can be a bit confusing on the developed view of the outer cone ,if you put a rule on the centre point where all the lines join and swivel it to touch the inlet of the blade it is straight into the flow parallel to the engine shaft. The Kamps shows an angle 25 degrees off the air flow, Kurt does not quote it but looks 15-20 don't think it's too critical. Good idea to just photo enlarge it from the book to check , something I would do.
Gone through all my posts and added notes or changed it to make it clear,if something does not make sense let me know. Don,t think it matters which way the hooked tubes go as the air just comes striaght out of the walking sticks,do it the same as the 631 camber,if it's the wrong way now you've made it don,t bother about it. Mark on the 631 combuster drawing has bent the last 15 of the tube towards the nexted stick this is to make the air swirl round in a dough nut pattern hope that makes sense.( may edit later!)
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reedy
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Post by reedy on Jan 21, 2017 8:16:56 GMT -5
Hi Jeff
Quick reply to your setup, I've made a few Kamps NGV,s. before I had it welded I found an old big brass nut which I bored to about 68 mm i/d then with the stainless flange I was going to weld on I marked out the 12 holes as accurate as i could and drilled them clearance ,I then put that on the brass nut located with the outer tube of the ngv and transfered the hole pattern tapping holes in the brass,bolting it on with all 12 bolts then had it welded ,helping to back and cool the weld trying to stop it pulling the flange forward,it still did it but less,took it off the brass then stress relieved it put it back on with all 12 bolts and griped the brass outer in the lathe to min m/c turbine area. your set up may make the housing area oval if you have only camped it in two places, just something to check when off the m/c table.mine still moved that's why I like to make my clearance tight and check when bolted to the engine, hand grind with a dremel any offset or tight spot. sometimes i think it's the way its fitted to the can ,if the end is not square.it will still move or twist if yo get a very hot start as the ngv blades can destort.the cast ones can be just as must trouble if you have hot starts, I took a Ram engine apart because it keep catching and found half the ngv blades had cracked at the root. Lots of ways to skin a cat ! A jet engine is a hard taskmaster but you do learn a lot,mainly how to pull your hair out.
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reedy
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Post by reedy on Jan 21, 2017 10:56:17 GMT -5
Found this on the internet looks good for home build for a car compressor wheel kj66 or increase o/d for kamps, 21 degrees same as Kamps 69+21=90. Wish I'd see this when building my KJ66 . think this website has the plans www.john-tom.com/html/Jet.htmlJust read on build thread they tried it and found gently curving blades as per Kamps better, guess to much drag from all the blade leading edges.
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Post by jetjeff on Jan 21, 2017 11:18:33 GMT -5
Hi Chris, Thanks. I drove into my office in Flint to make some 140% enlargements of the Schreckling compressor. Wow, I was off by a good margin with my 1st carbon compressor, probably explains why she was running hot. Not sure why I didn't think of this before, sometimes it takes a little coaxing of the two brain cells I have left, to hold hands and fire,,,lol. Regards Jeff
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