Gearbox Modification.

[turbochris]

That's f'n sweet! make sure yo tear it down and check it as you build up power. Watch the temp and magnets.

[gidge348]

Thanks Chris, the good thing about this gearbox is that you can get to all the bearings etc from the outside of the box plus be able to see the gears.

That way I can leave the box mounted up and just take off covers to see what is going on without a full removal & tear down.

Of course if there is a problem it will need to come out but probably an hour all up to remove and re-install the lines and covers.

Regards
Ian...

PS Have you down loaded the manual I sent you the link to?

[gidge348]

The Saga episode 12.

Well, it has been a while since I posted but I have been busy,,,, Its hot,,,, I'm lazy..... (Inset excuse here)

Firstly before Christmas I dropped down the shaft to the heat treater and got it back early January.


At about the same time Jon (cursorkeys) sent through about 500 pages of the Maintenance manual dealing with the gearbox (Much appreciated). It gives a very detailed breakdown on the procedure for re-assembly of the gearbox so I stripped it down and have been going through (as much as possible) the procedure.

A few of the bearings and some clearances are slightly over spec but not by much so I guess I will need to live with that.







The hardest thing I find at the moment has been trying to get the tip clearances right.



The manual gives a specification of a mean centre of between 2 thou and 5 thou so I have been spending a few frustrating weeks trying to get this right while keeping the NGV to FPT clearances within spec in 4 or 5 planes AAAAAAAAAAAGGGGGGGGGGGGHHHHHHHHH.



Will get there, but it is the sort of job that I get done for and hour or so then frustration takes over and I need a beer.

Cheers

Ian...

[turbochris]

when someone who knows a nimbus sees that gearbox they'll be like what the fu...... nice job!

[gidge348]

Been a while so I thought I had better post something.

The Saga episode 13.

Finally got the tip clearances right and found out why I was having so much trouble. It looks like during manufacture the blades on the NGV and face of the NGV housing are not parallel when it was originally welded together in the factory It measures about 0.5mm deeper on one side than the other. I never thought I would see something like that in an engine, but I guess it has worked in the past so should still work now.

I have the gearbox and exhaust all fitted up now.





View from the rear.

Tonight I am going to make up some temporary engine mounts to fit it to the build table.



The next thing is to get some pipes welded for the governor move and shortening the scavenge lines for the gearbox. So knowing my limits I will drop them down to the guy that welded the box and while that is being done I will get into modifying the wiring harness.

Cheers

Ian...

[racket]

Hi Ian

One fine lookin' engine :-)

LOL.......yeh , aircraft grade bits aren't always "perfect" , I was rather taken aback when I spun a C20 4th stage turbine blisk on a mandrel in my lathe, it wobbled axially , well the cast blades did , the outer labyrinth seal was perfect , so was everything else that was machined , it was just those wobbly blades that got me.

Things are moving forward with your build now that the engines been modified , just weld a few lengths of pipe around her , fits some wheels and you'll be ready to roll :-)

Cheers
John

[gidge348]

The saga episode 14.

Have been messing around with the drawings for the car for a few weeks but have put on most of the welded lines now, had to get in a couple of new fitting and make up new fittings for the fuel lines. Then I will try and start the engine to make sure everything is OK before going further.

After reading Anders working on his gearbox I though I may as well get stuck in my diff and try and work out the oiling system.

Firstly the pinion


John recommended that I try and get more oiling to the pinion as this will be spinning at some silly speed. The Pinion is in a cartridge with 2 taper bearings either side.



The ideal situation is to pump oil into the centre and let the oil drain through the bearings from the narrow inside to the wider outside.

The problem is that bearing race is as hard as anything and drill bits wont touch it.

Spoke to a friend of mine and he recommended using a "masonry drill bit" ie. the type for drilling concrete and grind an edge to it.



I wont say it drilled easily but it did drill and cut a neat hole, needed a fair bit of cutting compound & oil but I was surprised how well it worked.



Cheers Ian...

[beaker]

Carbide kicks ass, if you ever have to do it again I recommend an Artu drill.
Very similar to a masonry bit but ground to cut metal and other materials
Awesome project can't wait to see it run.

[gidge348]

Thanks for that, I will keep an eye out for the Artu drill's, I was surprised how well the $2 masonry bit worked though.

Cheers,
Ian...

[turbochris]

How was that bearing assembly originally oiled? Why don't you just put it all together and spin it and see where the oil goes? Make a few small holes in the thing where you want to see oil and if oil pisses out you're good to go!

[gidge348]

Hi Chris, I have 2 problems with the diff I am trying to fix here.

Firstly the standard diff is a speedway type and the pinion only sees a max of say 8000rpm on the race track and the bearing are rated to about 11,000 rpm in a oil bath.


With the salt lake racer because I am chasing a higher top speed the pinion will be running at up to 15,000 rpm.

After talking to John he said that a pressure oiling would give the bearings a better chance of survival.

Second thing is I am running the diff upside down for ground clearance and to get the rotation correct.



So I am planning on running a 12v pressure pump through a filter to circulate oil to the pinion and to both ends (and bearings) on the input shaft that now will run dry at the top of the diff.



Cheers Ian...

[gidge348]

Forgive me Racket for I have sinned..... its been 6 months since my last post.

I have finished the engine assembly, mounted in the rack and I have got the Tierney ready for the start of the engine with the modified Gearbox.


Dash Board


New Gear box output


Oil Cooler


Ground start


Ground start Dash


Did a short run of the ground start to make sure all is ok.
www.youtube.com/watch?v=vzTVieCAaCc

Have run it up and has 30lbs+ oil pressure and spent a couple of days chasing oil leaks.... cheap Chinese "O" rings are not the thing needed to replace most of the ones I replaced earlier.

Just waiting for a friend to turn up tomorrow so we can get a full run of the engine and will load video when that is done.

Cheers Ian...

[racket]

Hi Ian

You have been busy,...... she's looking good :-)

All the best with the test run

Cheers
John

[pitciblackscotland]

Hi Ian,
Looking forward to the video, good luck with the test run. Nice APU Mmmmm yes oil leaks I'm fixing leaks at the moment on my GTP 70 engine.

Cheers,
Mark..

[Richard OConnell]

Nice work, looking forward to a video of it running