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Post by wannabebuilderuk on Dec 10, 2021 6:06:02 GMT -5
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Post by andym on Dec 10, 2021 11:15:13 GMT -5
Hi Ben/Scott Yep I like you did think making your own trailers had been outlawed... when I looked into it, others said yep all homemade band, others.... as long as they are built to a high standard most traffic cops would not have a problem... other told me it had to have maker plate, load rating etc..... But also try to get your head round the rules on driving with a trailers, the weight rating etc.... having to have a test for some classes. Real mess..... but can understand why.... you ask most what max speed is when you have a trailer on.... they dont have a clue |
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Post by slittlewing on Feb 11, 2022 14:50:58 GMT -5
You are correct mate, it’s been designed for those standards 👌 Been super busy of late, moved house again (two days before Xmas) and currently in the worst time of year work wise with long hours. The garage in new house had a single power socket and two light bulbs, so first job was to change that to a proper ring with loads of sockets and 16A welder supply, white walls, LED lighting and new shelving. It’s now suitable for working in! Next thing was to treat myself to a small lathe and milling machine which I have been on the look out for a very long time. Got a great deal on a pair which should be perfect compromise for 90% of the jobs I have, versus space available!   visualize json onlineCheers Scott |
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Post by slittlewing on Mar 20, 2022 15:03:23 GMT -5
Hi all,
A little video of the second fireup of Jet Kart, following the engine rebuild.
Unfortunately there was some oil being burned so some kind of internal leak, likely causing quite high TOTs for idle P2 (0.5bar).
The good news is the increased clearances between turbine and NGV seem to have fixed that issue 😃 so more work to do but one step at a time!
Cheers
Scott
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Post by slittlewing on Apr 4, 2022 15:54:29 GMT -5
Hi Guys A few pictures of the mods to the engine to fix the oil leak issue. Lead in added on the enlarged bores for the new oil fittings with piston style o ring seals. Made an interference fit sleeve to provide o-ring ID support for the oil connection between main housing and comp diffuser. Also took the opportunity to machine a groove into the OD of the journal bearings to provide oil to all holes simultaneously.            Engine static pressure tested OK 👍 Cheers Scott |
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Post by andym on Apr 11, 2022 1:47:33 GMT -5
Sorry Scott that I am not able to help you with the oil system issue... not having the issue myself with the engine... not sure what effect the changes you have made will effect things.
As for putting a grove in the journal bearings, I had the same idea until I spoke to Andy... the owner at AET Turbos, when he expalianed why the companys dont do it, it was clear and easy to understand
It is nice to see the engine run again, looking forward to seeing the afterburner run
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Post by slittlewing on Apr 11, 2022 17:13:07 GMT -5
Hi Andy,
Some manufacturers use grooved bearings, I think it’s worth a try as in a normal turbo the bearings are softer than the cast iron housing, but with an aluminium shaft housing it feels “safer” to get more oil around the OD.
Cheers
Scott
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dieselguy86
Veteran Member
Joined: September 2014
Posts: 187 
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Post by dieselguy86 on Apr 11, 2022 17:38:25 GMT -5
Reason for the grooves is not to get oil to all the holes, that's the "scallops" job.
The grooves on full floating bearings reduce the centrifugal pumping affect on the oil.
On semi-floating bearings the grooves DO distribute the oil to all the holes.
-Joe
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Post by racket on Apr 11, 2022 17:59:15 GMT -5
Hi Scott
Yep , lotsa different methods used by the manufacturers , there are considerations of lube pressure that come into their designs , because the "bush" rotates at around half shaft speed the lube holes in the bush act as centrifugal pumps preventing oil getting to the shaft unless the pressure is high enough to overcome the pumping force .
The crescent groove in the shaft tunnel over a segment of the bush OD creates a "wedge" that increases the lube pressure force attempting to get oil through the hole/s which then allows a lower oil supply pressure to be used.
The designs with non rotating "floating" bushes can get away with lowish pressures as well .
If an engine is designed with only a modest oil pressure when its up to temperature , that pressure might not be high enough for the turbos requirement if its pumping high boost levels/rpm , hence the need to use "wedgeing" or very thin sections in the holes to minimise pumping pressures .
The main thing is to get plenty of oil to all surfaces to keep the shaft's dynamics under control as well as its temperature
Ideally a cast iron housing for the bushes is whats required for long life , but thankfully our relatively short duty cycles let us get away with alloy .
Looking forward to video of the A/B on full song pushing the kart along at a high rate of knots, she's a beast :-)
Cheers
John
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Post by andym on Apr 12, 2022 1:46:50 GMT -5
Hi all every thing you have all said is true.... but the thing worked before, the bearing worked ? so why change.... ? not saying its going to be a bad change, but you just dont know.
Things have not been running right... get then engine running right, then make changes.
I would of not touched the front brass thrust bearing
But I still dont understand why an engine that did not leak oil, well a little from the piston ring seal, but thats normal, why is it burning oil ?
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Post by slittlewing on Apr 16, 2022 0:26:41 GMT -5
Hi all every thing you have all said is true.... but the thing worked before, the bearing worked ? so why change.... ? not saying its going to be a bad change, but you just dont know. Things have not been running right... get then engine running right, then make changes. I would of not touched the front brass thrust bearing But I still dont understand why an engine that did not leak oil, well a little from the piston ring seal, but thats normal, why is it burning oil ? Reason for oil leak was lack of ID support on o-ring groove between shaft tunnel and comp diffuser plate. This has previously been got around by using a very oversized o ring, as shown on first strip down:  Fitting one of those runs the risk of being extruded between the two faces which could cause the comp plate and snout to sit “not square” to the shaft tunnel upon tightening everything up. So I tried to use an o-ring appropriate to the groove size (groove 10mm OD, 1.2mm deep) which meant using a 10x1.5 o ring. However the groove is only 8.2ID so the o ring was neither properly supported or compressed, and leaked. Addition of press fit insert solved the issue:  Reason for bearing mod was because the brand new bearings looked slightly marked on the OD after the very short run at idle and 5bar oil pressure. More oil flow cannot be a bad thing in my view… but if it’s worse in some way then no big deal, bearings are £8 each to replace. Mod to thrust washer was a no brainer, I don’t fancy a 1kg rotor spinning at 60krpm behind my head, with the rotor thrust load being reacted only by a pair of low grade m3 screws. Cheers Scott |
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Post by andym on Apr 16, 2022 2:52:28 GMT -5
Nope.... The engine ran fine before and did not burn oil..... but clearly Soctt you know best.... Oh and if the oil can take an easier route it will do.... it aim is always to go from High pressure to low. Come on the engine left me working, ready for the track.... and now spent year or nearly 2 in bits..... and lets not start on the afterburner was not working, it would of done, just needed a little more time setting up.
"Mod to thrust washer was a no brainer, I don’t fancy a 1kg rotor spinning at 60krpm behind my head, with the rotor thrust load being reacted only by a pair of low grade m3 screws" in real turbos the dont even have screws, just pins.... not low grade either.... or did you say low grade for effect
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Post by madpatty on Apr 16, 2022 5:54:26 GMT -5
In the HX82 CHRA that I have, the thrust bearing is axially supported (or axially locked)by using precision shims in a groove created between the two mating faces, the top compressor plate and the rear bearing housing, which are held together by 6 xM8 bolts.
Pins are just used to restrict any rotation of the thrust bearing.
Regards
Patty
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Post by slittlewing on Apr 16, 2022 6:16:23 GMT -5
Thanks for accurately describing that Patty! I have mentioned it twice already  ( jetandturbineowners.proboards.com/post/32550/thread) maybe 3rd times a charm? Its really not that difficult to understand.. Low grade screws, yes. Stainless A2 screws are weaker than Mild 8.8 grade which is what you put ikea furniture together with. Not an issue if properly sized obviously....Now replaced with M5 12.9 grade. A shim solution to the comp diffuser would ultimately be strongest. |
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Post by slittlewing on Apr 16, 2022 7:18:23 GMT -5
FOR SALE ONCE IN A LIFETIME OPPORTUNITY
I 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.
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