ScottsCrazyBuilds Jet Kart

[andym]

What ever Scott, the engine did not stop becuse of rubbing, but i think the rubbing was cause by excessive heat, either at start up, or on other failed starts.
In the video the engine spools up a little more shortly after starting, which could only heppen because the engine found more to burn, and burn in the wrong place, lots of fuel was ejected from the engine when it did start, which would not of been there if the drain was conected, 

The Last time i ran the engine all was well, the first time you run it ?

Nope thats not the reason oil is leaking in. Am sure John can explain

O rings work better when they are seated, but what would i know, but i know oil ring set up like you want to do, will fail before mine would

5 Bolts work fine, and as for the little break, did any oil leak, nope, so a nothing issue

[slittlewing]

I will continue to fix the shortcomings of your engine.
You are right about one thing - the first time I start it, it’s fubared after 10 seconds... but you don’t see me complaining at you for it.

If you wish to pretend the engine wasn’t slowed down by the huge pieces of melted inconel on the NGV, and the hammered thrust bearing that’s fine 👍

For the benefit or interest of the rest of the forum members there will be more updates soon!!

[slittlewing]

Hi Chaps,

A little update, the rebuild kit arrived and it looks spot on 🙂
Next up will be rotor rebalancing!!

I have also been measuring all the o-ring grooves and sizing new/slightly different cross section ones as a few are a bit overcompressed or shaved.
The black one that sits against NGV plate has melted so I’ll use viton with the hope it can withstand the temps.





Cheers

Scott

[racket]

Hi Scott

Won't be long and she'll be ready to fire up again :-)

Cheers
John

[slittlewing]

First post in the “rebuild” chapter… a big Thankyou to Richard S (jetric) for rebalancing the rotor on his machine for me earlier this year 👍👍



We got it to the point where it was really nice and low readings on both ends and it couldn’t be further improved 😃 

Cheers

Scott

[Sweetenough]

Nice to see that you are back in business Scott!
Looking forward to hear the engine roar on full AB!
Have a stupid question that I have been thinking about for a few years now....
How do you "mark" the position of the compressor wheel relative to the turbine so that it can be put together the same ballanced position in the engine?
Kind Regards
Thomas

[racket]

Hi Thomas

To mark alignment I use a Dremil with a cutoff disc in it , a small cut/nick on the edge of the shaft end and at the outer edge of the comp snout is sufficient

Cheers
John

[slittlewing]

Many thanks!! John’s idea sounds very sensible - I have been going with coloured “paint pen” on the turbine and comp outer diameters, to be lined up on rebuild!

[slittlewing]

Next job was to modify the oil inlet within the comp back plate, so that a conventional “piston” type o-ring seal could be used on the feed tube.
The previous oil feed bore was 10mm. Using a 10mm feed tube with 2mm wall thickness would mean an ID of 6mm which felt a bit narrow. So I decided to open the bore up to 12mm (same as the oil outlet). 

I don’t have a mill so this would need to be done on pillar drill, but had to be very precise as there isn’t much wall thickness to play with. 
So I 3D printed a jig which I could use to get the diffuser vertical and clamped down on a pillar drill:





The existing bore was therefore drilled out from 10mm to 12mm and then reamed to an exact 12.18mm for accurate o-ring compression.

I also realised the thrust bearing was held with only 2 M3 bolts, as it isn’t clamped by the comp plate. I was a bit nervous about the whole forward thrust load acting on these two tiny fixings, so I increased them to M5 bolts which are about 3 times stronger. Couldn’t fit anything larger either in terms of the height or width of the cap head. The thrust bearing material was very difficult to drill (seemed to be “snatchy”)

Old M3 bolts:



New M5 grade 12.9 bolts: 






As mentioned before the journal bearing feeds have been widened to always reach a feed hole no matter the rotational position:




One theory on the turbine contact was a hot spot on NGV rear wall due to blocked injectors or uneven fuelling. I checked the needles with propane and they look good. There was a temptation to ultrasonic clean this but I decided not to incase it damaged or fatigued the needles which are quite delicate!! 



There were a few pulled threads which are now helicoiled and should be stronger than before. Was tempted to do every single thread but decided against it as they wouldn’t have been as accurate in positioning as the original CNC tapped holes.

Cheers 

Scott 

[andym]

Hi Nice work

but just so you know, the thrust waser in the turbo is held in by 2 split role pins and the front cover, no real reason to change...

Dont yet see how your changes on the oil in line will help.... what was there worked find, not perfect perhaps..... but much of our engines are inperfect.... hindsight is a wonderful thing, the second engine would alawys have improvements. This 12.8m referance ? for prper "O" Fitment, the "O" and suport rings are spec to the oil line, made bespoke ?

[slittlewing]

Thanks! Trying to do it justice and it’s nice and clean again now 😁

With the original turbo the thrust bearing load is spread across large area (front cover) and the split pins are just anti rotation. With the 2 fixings the thrust forces are on two point loads which seemed very high for M3s. So the upgrade to M5s was to add some safety margin.

The new oil fitting and drilled/reamed hole is another “peace of mind” mod, wasn’t confident I could get it to reseal first time and now any expansion of casing under pressure, or installation depth etc shouldnt matter at all.

Cheers

Scott

[slittlewing]

A few more rebuild pics and details. Marked rotor with pen for alignment:



Cleaned housing Assy:



Was a bit nervous about this O-ring extruding through its bore due to no wall on the ID but used some silicone to “hold it in place” whilst assembling, hopefully all good!



The NGV with its extra clearance thanks to my mate Carl:




Lockwired fuel rail (first attempt at lock wiring):






The lovely compressor… hand for scale.



NGV with pre existing “spot welds” to the rear wall



After some deliberation I decided to fully weld the NGV fins to the laser cut back wall to increase ridigity. There wasn’t any deformation after welding that I could see








The old T2 boss fell out on the last fireup and leaked so I installed a new compression fitting specifically for a 1.5mm thermocouple, and welded to outercase.





Coming together slowly…

Cheers,

Scott

[slittlewing]

Hi All,

An update that’s actually from months ago.. thought I may aswell post as things are a little quiet!

I had some “holiday” to take from work back in spring and nowhere to go due to covid. I decided I needed a trailer to be able to take the Jetbike and kart for testing when required, without always asking to borrow my mates.

I also had fairly specific requirements for it.. it had to be able to fit the kart (2.4m long) and wide enough. I also wanted it to be low to the ground so the ramp angle was minimal and easy to load. Lastly I wanted storage in the front for scuba bottles!

Some design work later.. 



Steel ordered and cut: 



Getting the base dead square and flat (on uneven garage floor) was crucial and a bit time consuming.




Sides going on:








Coming together but taking over the garage!!




A fair amount of laser cut parts were used:





Plates added for screwing down “lifting eyes” that can be used for tie downs (bike or kart)



Two pack epoxy paint after many hours cleaning off grease /“mill scale”



Finished:





It took 2 full weeks to build, and to be honest I could have probably have bought a trailer for the end cost 😂😂 however… hopefully it will last many years to come 🙏🏻😆

Cheers

Scott 

[andym]

Nice trailor


Hope you dont need to take ngv back plate off at some point, no need to weld fully, John dont fix his.. 

Please make sure you cover front of engine and perhaps rear.... 60mph is plentty to let comp wheel windmill.

[pitciblackscotland]

Hi Scott,
Nice trailer build, i need to get one soon for my trike

Cheers,
Mark.