Gearbox Modification.

[gidge348]

The saga episode 6.

Now it is time to "Get Medieval" on the gearbox.



Firstly marked up the front of the gearbox for the area to be removed. Note I want to keep the 4 through bolt holes that mount the gearbox

to the gas generator and the engine mount on the side of the sump area.



The original length of the gearbox is about 612mm



The area delicately removed with a drop saw and an angle grinder....pretty it ain’t 



The “new” gearbox mounted on my jig plate I wanted to buy a piece of 12mm mild steel, but I found a piece of 16mm 350 grade surplus to requirements at a friend’s work (free).



Finished Length 450mm, I was hoping to get down to 435mm but this is close enough.

Next thing is welding the pieces together. I can stick 2 bits of aluminium together with a mig, weather you would call it welding is another story. I will give it a go and if it's no good I will get it done professionaly.

Cheers
Ian...

[racket]

Hi Ian

In the best tradition of DIY turbine building :-)

Cheers
John

[ozbooster]

Looks good Ian
If you were a few kms closer i could weld it for you, been doing lots of tig work on my turbo stuff
there actually not badly priced now compared to 6-7 yrs ago if you had a continuing need

after pulling it apart how does the intermediate shaft and gear  look for strength when its not got the gears on its output for reactive force
i think that was one of my main concerns when i started looking at mine was it suitable to do more than transfer power to the next gearset 

[gidge348]

Oct 9, 2013 19:14:27 GMT -5 ozbooster said:

Looks good Ian
If you were a few kms closer i could weld it for you, been doing lots of tig work on my turbo stuff
there actually not badly priced now compared to 6-7 yrs ago if you had a continuing need

after pulling it apart how does the intermediate shaft and gear  look for strength when its not got the gears on its output for reactive force
i think that was one of my main concerns when i started looking at mine was it suitable to do more than transfer power to the next gearset 

Thanks Greg, I would take you up on the welding, but 3500kms is a bit far for a day trip

Good question on the gear, I am not sure what is meant by "when its not got the gears on its output for reactive force" I hope to outline my thinking here and see what you reckon???

I have just got it back from lab and have the results.. and a few surprises (but not in a bad way).

Gear has chemistry similar to EN 39B but may be proprietary steel?

Gear chemistry..........................EN 39B chemistry

1.25% Chrome..........................1.0-1.4%
4.2% Nickel..........................3.9-4.3%
0.27% Molly...........................0.15-0.35%
0.35% Silicon.........................0.1-0.4%
0.5% Manganese.......................0.25-0.05%
0.25% Carbon (difficult to get exact reading may be lower) EN 39B is 0.12-0.18%

The surprising thing is that the large gear and small gear are "2 different gears stuck together" possibly some type of induction or friction welding?



It carries all the torque through this joint now so there is no reason to think it won’t do it in the future. I will be machining the spline beneath the secondary gear.





Current hardness is 380 Vickers or 1220 MPA. ie Not particularly hard but they could not get an exact harness inside the shaft.

The area seems to be induction hardened not case hardened so the recommendation on the shaft is to go no higher than 360-380 Vickers hardness.

With regards to the shaft steel obviously EN 39B would be the first choice but after talking to the heat treater he said EN39B "shafts" when treated seem to deform more than other metals so the recommendation was to use normal old 4140.

Now if the outer shaft, inner shaft, splines should take the strain............ Firstly I reverted back to the clever people at Rolls Royce and took the dimensions of the standard output shaft and the 2250rpm output and EN 39B as it appears the same.





Then I input the results into www.zakgear.com/External_Spline_IN.html

From there I can up with a 2.0 or better safety factor on the shaft & coupler.

I then went to spline on the yoke of a 9" diff and put those splines on my drawing and came up with a safety factor of between 13 & 50.

I then used the same type of splines as on the standard coupler and came up with 13-110.

Then I went further down the drive line and the drive shaft to the diff.



This is the drive shaft I want to use, its used in Sprint Cars with 500-600 hp piston engines and a lot of banging and crashing. In the streamliner it should be a long slow pull (more HP I know) but in general looks about 50% the strength of what I am planning on the nimbus gearbox.


Anyway, that's the theory so any comments welcome...


Ian...

[gidge348]

Set up my MIG to try and weld the aluminium gearbox but unfortunately I could not set it for negative earth without tearing the whole thing apart.

So tried a few weld on some test pieces and the best I could come up with looked like a small creature with diarrhoea had walked across the weld.....

So I have dropped it down to get it welded properly.

Have almost finished the bearing housing and seal holder, as soon as I have I will post pics.


Ian...

[wolfdragon]

Wish you were near Maryland, I've got a TIG and am masochistic enough to think aluminum is fun to weld....

[gidge348]

Thanks for the offer Wolfdragon, one of the problems living in Perth is that it is the world most isolated city....

Just a quick question on oil pumps to you all. I need a pump to circulate oil in the diff & governor and was thinking of something like this?

www.ebay.com/itm/New-12v-Differential-Transmission-Oil-Cooler-Gear-Pump-Unlike-Mocal-and-Tilton-/280782675244?pt=Vintage_Car_Truck_Parts_Accessories&hash=item415ff39d2c&vxp=mtr

Does anyone have any views (good or bad) on these things?

Ian...

[gidge348]

Back to the saga episode 7

Have been trying to get accurate measurements on the inside of the gear shaft so I can make the shaft to fit, it starts wide and then tapers at some point in the middle to a smaller diameter and I need to know the points at which it tapered from one to the other. In the end I used my lathe and the Chinese DRO I bought a few months ago. The DRO has to be one of the best things I have bought in recent times.




Just finished up the bearing assembly that replaces the piston assembly for the torque sensor.





The parts are firstly the housing I made, second the standard Nimbus thrust bearing, third 7.5mm aluminium spacer, fourth Nimbus lock washer fifth nimbus lock nut, and 2 O rings. Behind is the nimbus piston and cylinder (not used)



Parts assembled this the side that faces the gearbox the additional hole on the circumference is for the oil drain. I have not bent up the lock tab as yet, may need to pull apart.




This is the rear face that faces the seal holder the three grooves around the bearing are so I can press it out if necessary. In the nimbus torque sensor the bearing is oiled via the pressure sensor and then drains out back to the main gearbox. I am setting up a oil squitter on the seal cover to face back to the bearing and drain out by the hole in the lower right corner to the standard nimbus drain.

At the moment I am just trying to track down a 1/4 npt bottoming tap to finish the seal cover once the 2 parts are together it will probably make more sense.


Ian...

[racket]

Hi Ian

Parts starting to come together nicely :-)

Heh heh , bottoming taps ...........I generally get the side grinder going with a cutoff disc and lop off the cutting end of a worn/tired intermediate tap , then purchase a new and easily sourced replacement intermediate ........then I've got two good taps .

Cheers
John

[gidge348]

Oct 17, 2013 16:44:55 GMT -5 racket said:

Hi Ian

Parts starting to come together nicely :-)

Heh heh , bottoming taps ...........I generally get the side grinder going with a cutoff disc and lop off the cutting end of a worn/tired intermediate tap , then purchase a new and easily sourced replacement intermediate ........then I've got two good taps .

Cheers
John

Doh... Why didn't I think of that will get stuck in.


By the way John, how are you getting on with the fires? I hope you are well out of the way...

Ian...

[racket]

Hi Ian

Yes, thankfully the fires are either to the north or south of us , Crowdy National Park ~10klms to the south has been burning for a couple of weeks and has burnt out >4,000 hectares with the smoke blanketing us whenever the wind is from that direction , yesterday a big fire started up ~50klms to the north ...........luckily we had ~15mm of rain last night ( first for about 2 months) in a thunderstorm and temps today of ~19 deg, ..... whereas it was ~36 degrees yesterday with humidity down in single figures , sorta like those hot dry easterlies you get in Perth, great for fires .

When I was living in Sydney back in the early '90's I had a big fire burn out my bush block property , thankfully it came through in the evening and we had a heap of fire fighters there to protect the house , some of the fire fighters were from South Australia , they'd driven their appliances the >1,000 klm to help the local guys who were stretched to the limit as there were a huge number of fire right across NSW at the time.........Sydney was ringed by fire and was burning :-(

About 7 years ago we were living in the Blue Mountains (near the current Springwood fire)and were woken in the middle of the night by a neighbour banging on our door telling us the valley just across the road was on fire ( kids again) and we'd better get ourselves organised to fight the ember attack ........ah, the joys of living in this sunburnt country :-)

Cheers
John

[gidge348]

It is definitely a strange country we live in, I am in the Perth Hills in Gidgegannup (gidge) and by this time of the year we are usually brown and dry, but at the moment everything is still as green as the middle of winter.

We are still expecting rain this weekend almost like we did not get a spring this year and we are still in winter ?

I guess El Niño or La Niño are really going this year.


Ian...

[gidge348]

Have been trying to turn down the drive shaft on my lathe, the shaft is 4140 and looks like it will take days to finish.... Well a friend of mine just turned up and he has all sorts of CNC machines at his work.....

So cut to the chase I "threatened" him with a carton of beer and he is going to turn it for me....


Ian...

[gidge348]

The saga episode 8


Been busy, but not much to show for it at the moment.

Firstly the output shaft has been machined, but I am awaiting a recommendation on the size and type of splines from a smart man that does FEA (finite element analysis).

The gearbox was dropped down to one fellow who wasn't happy with welding the cast gearbox so I have dropped to someone else, but the are heading to the US next week & I hope they can get it done before they go.

I am still waiting for the seals to turn up but while I am waiting I have been finishing off seal holder and oil squirter system.




This is the seal holder with tube fitting and at the top leading to the recessed hole in the face.




This is the oil squirter with an O ring to seal against the face.




Oil squirter attached, will just Loctite and centre punch the screws once I have it all together.




This is the bearing shown earlier fitted to the seal holder. The oil squirter points at the bearing and drains from the bottom of the bearing housing.




This is a sprint car torque bell that will cover the uni-joint and drive shaft on the way to the diff.


I have been doing some work on attaching the governor to the rear housing and should have that done in the next few days.

[racket]

Hi Ian

LOL.....Things always seem to progress at a snails pace ..................I sometimes think I'm going backwards when I hit a brick wall of indecision about how to progress forward :-(

I can understand the welder's reluctance to have a go at stitching the gearbox together , warpage is going to be a problem unless its very rigidly clamped , even then you might have to get the cases heat treated to relieve stresses and the faces skimmed off to true things up.

Seal holder is looking good :-)

Cheers
John