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Post by finiteparts on Apr 16, 2022 11:25:57 GMT -5
All,
Come on, let's respect everyone's opinion here. It is the varied ideas, views and knowledge that make this forum fun and helpful.
Andy made a very nice engine and I think he should be very proud of it. In any design, there is usually refinements and upgrades that can be done to make it even better and taking constructive criticism should be encouraged to help all get to more refined engine designs.
But, I also agree with Andy, that changing things like putting a groove in the bearing is a risky venture, especially when there doesn't sound like there is a strong reason to do it.
Rotordynamics are tricky and tweaking them is risky. Floating journal bearings (FJB) are essentially two journal bearings stacked in series. The inner journal has tighter clearances to do the heavy lifting, while the outer film is larger to soften the bearing transmission forces to the housing and provide increased damping as a means to convect the kinetic energy out of the system. Putting a groove in the outer bearing land will reduce the stiffness of the outer bearing film and potentially change the ring speed ratio of the FJB due to the increased surface area of the outer ring, thus an increase in the torque acting on the outer bearing surface. Modifying the ring speed ratio changes the bearing's proximity to both the inner and outer whirl instability...maybe good, maybe bad...it is hard to say without analysis. The risk is, if you get into a whirl instability, the reduced outer stiffness could mean that the bearing will require a larger eccentricity to react the instability forces and you may rub and damage the rotor hardware. So I agree with Andy on the sentiment that if it isn't broke don't "fix" it, at least without analysis.
Being able to listen and constructively help each other will help all and push our hobby forward.
- Chris
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Post by andym on Apr 16, 2022 13:11:39 GMT -5
FOR SALE ONCE IN A LIFETIME OPPORTUNITYI would like to offer to the forum the chance to buy a GT40 with a home built racing engine. Its ready to race and I don't want to put it on ebay and have some knob buy it who doesn't have the skills to move it forward. You tell me not to sell it but I ignore you.
You might decide to modify it (being a project after all) and I will immediately throw my toys out of the pram and leave the forum like a 5 year old.
As soon as you get it home and fire it up "as it is" , the engine will seize. I will have the tenacity to complain at you for it, after all I have run it for about 3 minutes so it must be pukka.
Any modification you make, with sound engineering judgement, I will question and bitch about. Even though you are just trying to do best for the project and its not personal. When you provide credible information I will argue and make myself look stupid repeatedly.
My sole purpose to rejoin the forum will appear to be to turn your build thread into Jeremy Kyle and offer absolutely nothing useful. Did I mention this is for sale with *free* old owner EGO permanently attached (I mean the thing must be perfect because I built it)
Fucking tedious.
The engine left here fine..... I even offered to drive down to help you start it first time ...
We talked about working with you to get to the track and get the best out of it together....
Not like I done it before. my last kart still holds the record.... yes I felt snubbed, we talked for some time about thing...... working together.
Yes I sold it to you... some might say cheap, and yes I wanted to sell it, with the new car I had brought and my health meaning track meetings are harder for me now.
I wanted you to have it, after taking to you, you telling me you wished to get a world record some time in your life.
As like I said...... I hoped we would be working together on it..... Was willing to come to tracks, be there to help.... but that all went out the window once you got the kart.... yes I felt hurt I dont mind saying..... I had hoped I had found a friend. Someone I could work with moving forward, and be part of the next record kart
Next thing you started with the afterburner saying it did not work, even before it had been set up, you said it was not going to work, found falt with it..... even before you had run the engine....
You made changes before you had run the engine as it left me, had fail starts.... and the cooked the engine......you played with how the fuel pump was wired up
How else can you look at it..... the engine left here working ..... you get your hands on it and WTF.....
Like i said the 3 mm screws are more then the turbo companys use.... Every chance you have you find falt..... Let think your bike engine will not run without mekting the spark plugs..... you first engine ? so you ran the engine.... burnt it...... put it back together and it burns oil...... ? its only your sound engineering judgemnet ...... dont mean your right..... your track record dont hold up..... The after burner would of worked .... just like the 5 others i have made.... The Kart was track reddy..... if only for some setting up
Take your potty mouth else where...... too long, slow, or dull; tiresome or monotonous....... Nope.... but to you calling people names is about your level
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Post by finiteparts on Apr 16, 2022 22:02:08 GMT -5
Ok...let's figure out if the 3mm bolts were an issue.
Tensile stress area of M3 bolt = 5.03 mm, (0.0078 in^2)
Tensile capability of 316 SS or 18-8ph SS = 70,000 psi
- per bolt minimum ultimate tensile load capability = 546 lbf (2428 N)
- thus total thrust bearing minimum ultimate tensile load capability = 1092 lbf (4857 N)
Now let's figure out what the maximum forward thrust load is...
- I am not exactly sure what the compressor wheel outlet diameter is, but taking a swag from the part number on the back of the compressor, maybe a MAMBA Billet Turbo Compressor Wheel for HX82 Performance (110/152.04 mm) 8+8?
so the back face projected area ~ 28.14 in^2
and it states that it can run up to 70 psi, so the forward thrust load would be something less than ~ 1556.14 lbf (assumes 70 psi on backface and 14.7 on the forward side, which is more severe than the worst case). The aft thrust due to the turbine is relatively small, so we can see that the thrust load is roughly on the same order of magnitude as the minimum ultimate tensile load capability of the two 3 mm bolts.
So, just from a quick 'Rough Order of Magnitude' (ROM) set of calcs, the 3 mm bolts do appear to be barely adequate for the job. If I was designing the engine, I would have upgraded the two bolts also, by switching to 12.9 grade and thus having 2760 lbf of minimum ultimate tensile load capability. Jumping to the M5 probably wouldn't have been my first step though.
The nice thing about engineering is that we don't have to argue about things...we can let the numbers tell us what we need to know.
Akin's first law of Spacecraft Design, " Engineering is done with numbers. Analysis without numbers is only an opinion."
- Chris
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Post by slittlewing on Apr 17, 2022 0:19:20 GMT -5
Thanks for the Calculations Chris, I calculated the ultimate tensile load of the M3s previously and compared to total thrust it was basically similar, which is a big red flag. The reason for change to M5 is one for safety margin, but two also for stiffness I.e. minimised movement under load. In a real turbo it’s basically clamped and can’t move at all so in lieu of that, second best thing would be to put the biggest fixings in that will physically fit.
I consider the journal bearing mod low risk because some manufacturers do this anyway, also because replacement bearings are inexpensive if it is not an improvement. It’s an experiment 🙂
As for Andy’s comments… we have covered all of this previously. You wanted to be a part of it, I was more than happy for this too. However thats proven to be on “your terms”, of the kart not being touched 😂. The second I start playing with it, you take offence and block me, tell me you don’t want to speak anymore, moan at every modification, and after all that.. complain you aren’t part of the journey?!? 🙄 as I said, absolutely tedious.
The kart will have hundreds more modifications in the quest for speed and engineering enjoyment.
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Post by andym on Apr 17, 2022 2:05:31 GMT -5
Ok...let's figure out if the 3mm bolts were an issue.
Tensile stress area of M3 bolt = 5.03 mm, (0.0078 in^2)
Tensile capability of 316 SS or 18-8ph SS = 70,000 psi
- per bolt minimum ultimate tensile load capability = 546 lbf (2428 N)
- thus total thrust bearing minimum ultimate tensile load capability = 1092 lbf (4857 N)
Now let's figure out what the maximum forward thrust load is...
- I am not exactly sure what the compressor wheel outlet diameter is, but taking a swag from the part number on the back of the compressor, maybe a MAMBA Billet Turbo Compressor Wheel for HX82 Performance (110/152.04 mm) 8+8?
so the back face projected area ~ 28.14 in^2
and it states that it can run up to 70 psi, so the forward thrust load would be something less than ~ 1556.14 lbf (assumes 70 psi on backface and 14.7 on the forward side, which is more severe than the worst case). The aft thrust due to the turbine is relatively small, so we can see that the thrust load is roughly on the same order of magnitude as the minimum ultimate tensile load capability of the two 3 mm bolts.
So, just from a quick 'Rough Order of Magnitude' (ROM) set of calcs, the 3 mm bolts do appear to be barely adequate for the job. If I was designing the engine, I would have upgraded the two bolts also, by switching to 12.9 grade and thus having 2760 lbf of minimum ultimate tensile load capability. Jumping to the M5 probably wouldn't have been my first step though.
The nice thing about engineering is that we don't have to argue about things...we can let the numbers tell us what we need to know.
Akin's first law of Spacecraft Design, " Engineering is done with numbers. Analysis without numbers is only an opinion."
- Chris
Hi chris.... am sure your working out are spot ... my point was the turbo companys dont even put bolts there just rolled pins... but thanks any way |
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Post by andym on Apr 17, 2022 2:21:59 GMT -5
Thanks for the Calculations Chris, I calculated the ultimate tensile load of the M3s previously and compared to total thrust it was basically similar, which is a big red flag. The reason for change to M5 is one for safety margin, but two also for stiffness I.e. minimised movement under load. In a real turbo it’s basically clamped and can’t move at all so in lieu of that, second best thing would be to put the biggest fixings in that will physically fit. I consider the journal bearing mod low risk because some manufacturers do this anyway, also because replacement bearings are inexpensive if it is not an improvement. It’s an experiment 🙂 As for Andy’s comments… we have covered all of this previously. You wanted to be a part of it, I was more than happy for this too. However thats proven to be on “your terms”, of the kart not being touched 😂. The second I start playing with it, you take offence and block me, tell me you don’t want to speak anymore, moan at every modification, and after all that.. complain you aren’t part of the journey?!? 🙄 as I said, absolutely tedious. The kart will have hundreds more modifications in the quest for speed and engineering enjoyment. No Scott the moment your got the kart you wanted nothing to do with me Cutting the afterburner up, telling the world it did not work.... when in truth it had not been set up, and considering the other 5 I had made worked ..... Tell me how do you work with someone.... that dispite evdance that others worked, just starts cutting things up, We had even talked on the phone about it, you questioned it, and said it would be fine, just needed setting up. and the only reason i had not run it agian, was people had not been to happy me running it at home. Before you have even got to know the engine and systems. your cutting into the wiring...... changing how the fuel pump is run.only to cause problems, filling the engine with fuel... was this sound engineering judgment Scott call me all the names you want, in truth name calling is about your level..... Scott do what you want... your doing so well already... to think if you had just left as is, let me help you set things up better, taken it to the track..... good chance you would have the record already |
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Post by slittlewing on Apr 17, 2022 5:23:26 GMT -5
And there it is… 2 years of angst and whinging, due to your EGO not being able to handle me fitting a new afterburner fuel ring 😂😂 ridiculous.
The afterburner you built on this kart has not worked in your tests. You said the engine idle was too high on your last test, even though there were multiple ignitions of the AB and it should have just “run” all things being well. In my opinion the huge 3mm holes in your fuel ring are mostly to blame - due to poor atomisation (hence changing to 1mm holes in my fuel ring), and the second factor is that you ran the AB pump/fuelling at full tilt. I have fitted a PWM controller so it can be varied to match the mass flow ie boost pressure. The results of fuelling vs boost are well documented and tested for example in Thomas jetoped where the AB stops working when it’s too rich. The solenoid and needle valve you fitted to bypass fuel on the next attempt won’t help the above fundamentals so no, I didn’t bother trying it,
Take as much offence as you like - but soon enough I will fire up the AB with my mods and it will work ☺️. What then?
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Post by andym on Apr 17, 2022 6:35:41 GMT -5
And there it is… 2 years of angst and whinging, due to your EGO not being able to handle me fitting a new afterburner fuel ring 😂😂 ridiculous. The afterburner you built on this kart has not worked in your tests. You said the engine idle was too high on your last test, even though there were multiple ignitions of the AB and it should have just “run” all things being well. In my opinion the huge 3mm holes in your fuel ring are mostly to blame - due to poor atomisation (hence changing to 1mm holes in my fuel ring), and the second factor is that you ran the AB pump/fuelling at full tilt. I have fitted a PWM controller so it can be varied to match the mass flow ie boost pressure. The results of fuelling vs boost are well documented and tested for example in Thomas jetoped where the AB stops working when it’s too rich. The solenoid and needle valve you fitted to bypass fuel on the next attempt won’t help the above fundamentals so no, I didn’t bother trying it, Take as much offence as you like, Soon enough I will fire up the AB with my mods and it will work. ☺️ What then? lol.....my EGO..... what a total joke.... so how many afterburner you built..... again, you think you know it all.... the afterrburner would of work just like the 5 others..... but nope you knew better.... have have not said what you did would not work, but your first act of working together is tell and saying to every one that the afterburner would not work....... again YOU.... YOU its all it been you no better..... and nothing to do with my EGO.... we talked as i said about the afterburner, and dispite you cut it up, again.... on about it will not work this and that..... me and history telling you other your EGO drove you to fuck what andy and the 5 other afterburnersw prove.... fuck him, i know better.... its mine I will do what i want..... Like I have said I did think we had a friendship..... I look forward to helping you get the record.... I trusted what we had talked about, why I had faith in you having the project.... So one honest and true, standing by his word..... Summaryley cutting the afterbuener up..... ? Still stands, if left alone it would of been fine, and set new recorded ..... i will put my track record up against you any day...... The World Record Kart ran the same system.... and OH worked fine, and even with the 3mm holes..... the multiple ignitions happened like i said at the time, thing not set up, that was the first and only test of the afterburner. History showed it would work and work fine You realy do think your better than me, and any ideal you have is so much better But thanks.... again.... how well are things going, engine working well, afterburnewr tested, ready for the track |
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Post by slittlewing on Apr 17, 2022 6:42:16 GMT -5
I don’t think you answered the question. But anyway, I’m going to carry on making the most of the project - I joined this forum as an engineering hobbyist and last time I checked, I don’t think this forum is called dramaschool.proboards.com 😂😂😂 Stay tuned for more updates… |
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Post by andym on Apr 17, 2022 7:15:58 GMT -5
I don’t think you answered the question. But anyway, I’m going to carry on making the most of the project - I joined this forum as an engineering hobbyist and last time I checked, I don’t think this forum is called dramaschool.proboards.com 😂😂😂 Stay tuned for more updates… |
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Post by slittlewing on Apr 17, 2022 7:55:14 GMT -5
No name calling, just lots of unnecessary drama. Next up… more engine testing.
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Post by andym on Apr 17, 2022 10:28:29 GMT -5
"Fucking tedious" name calling in most peoples book
But there has been a clear lack of honestey and integrity.... but no drama, tell it how you like...
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Post by slittlewing on May 1, 2022 9:20:22 GMT -5
Hi All!
Finally got round to another engine test, post rebuild number 2!
A bit of a tricky issue to diagnose with the dash reporting healthy fuel pressure, but good to understand the dropping idle issue which I think has been present in each fireup thus far. It seems the return needle valve closes gradually over time after initial pressure application, causing fuel starvation.
I think the blue flames through the turbine would also finally explain the turbine expansion and rubbing problems in the first fireup.
Next I will be removing the existing fuel system and fitting a “returnless” one which is PWM controlled on pump speed. This would be the eventual setup with ECU anyway, so it should also help for finding appropriate settings for that in future!
Cheers
Scott
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Post by andym on May 1, 2022 15:12:13 GMT -5
Hi All! Finally got round to another engine test, post rebuild number 2! A bit of a tricky issue to diagnose with the dash reporting healthy fuel pressure, but good to understand the dropping idle issue which I think has been present in each fireup thus far. It seems the return needle valve closes gradually over time after initial pressure application, causing fuel starvation. I think the blue flames through the turbine would also finally explain the turbine expansion and rubbing problems in the first fireup. Next I will be removing the existing fuel system and fitting a “returnless” one which is PWM controlled on pump speed. This would be the eventual setup with ECU anyway, so it should also help for finding appropriate settings for that in future! Cheers Scott Left here working fine, perhaps something to do with you wiring in a speed control, or number of things..... but am sure some how you will find falt, and it will be something that i did in...... your humble view was wrong..... but seeing as its same system fitted to 4 other karts and engine I made, and had no issue with ..... Oh yes the Jet mini as well ..... perhaps try cleaning the fillter.... am guess you been filltering the fuel in to the tank |
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Post by slittlewing on May 10, 2022 8:10:54 GMT -5
Hi All, A little garage upgrade… fitted an electric hoist so I can lift the kart up and down from the work platform easily! Should be handy for working on the underside too, and motorbikes 😁 
Cheers
Scott |
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