"Fat Boy" 12/118 thrust engine

[racket]

Hi Guys

A few pics of the NGV mounting.

The triangle mounts are to prevent the NGV from "spinning" , the rectangular mounts are to position the NGV axially in the correct position and to support the gas loading , the "gaps" are to allow fresh air in and hot air out from around the NGV and to keep the outer tube a tad cooler .

Theres provision for lockwiring of the 4 X 5 mm screws which will be left a tad loose to allow for "expansions"





The NGV has been left as much standard as possible , just the 4th stage wheel shroud removed and its base machined down to 112.5 mm to provide a 0.5 mm diametric clearance in the 113 mm dia wheel shroud diameter , the 0.5 mm should allow some extra expansion of the NGV relative to the shroud as there will be some axial expansions so a bit of "slipjointing" required.

The triangular spin preventers are TIG'ed onto the flange that surrounds the 3rd stage wheel shroud that will now be the slipjoint for any interstage ducting.



And a coupla pics of the rest of the assembly





Cheers
John

[turboron]

John, could you post a cross section sketch to help us visualize your design?

Thanks, Ron

[racket]

Hi Ron

Its been an "organic" build so no drawing other than a few single item bits that I needed to draw up prior to machining .

The further I get into this build the less happy I am about it, its overcomplicated compared to the one I built for Andrews bike jetandturbineowners.proboards.com/thread/34/motorcycle-project

Adapting a ready made gearbox isn't always easy , there are extra bits required to be made , and it ends up a compromise .

I don't like the 2 stage gear redux for starters , instead of only a single high speed set of bearings and gears to lube ,theres two .

The 2 stage redux causes rotation direction problems when using the 4th stage Allison wheel which necessitates less than ideal placement of parts in a vehicle .

The current setup is heavier than my construction.

And last but not least , I've got big problems trying to fit pressure lube plumbing and bleed air cooling into the gearbox.

The gearbox/freepower will be a viable unit hopefully , but its ending up with too many compromises for my liking :-( ...... I wouldn't recommend anyone do a similar build.

Cheers
John

[Johansson]

Aug 7, 2018 17:08:18 GMT -5 racket said:

I wouldn't recommend anyone do a similar build.

That is funny, as soon as JU-02 is running I will be doing just that.

The upside is that I have the gearbox part sorted already so I only need to figure out a way to properly fit the C20 NGV to it.

[racket]

Hi Anders

LOL, the NGV is about the only part I'm happy with, you won't have any trouble doing it, I've left an ~5-6 mm axial distance between the NGV and wheel.

I spent the morning increasing the threaded hole size in the gearbox input shaft from 6 mm to 3/8" UNF so that I can secure the turb wheel with a substantial bolt , bugger of a job as I had to hold the pinion gear in the chuck ,a couple of thicknesses of plastic kitchen sink pipe around the gear gave sufficient protection when clamping down the jaws, the bearings were all taped up to stop rubbish getting into them .

Once that job was done I needed to make up a means of pulling the turb wheel mounting boss from the input shaft , a bit of 1/2" UNF thread tapped into it did nicely .

Then it was time for the crappy job of getting the air and oil into the gearbox, thankfully I'd already done some work on this , but still needed to add an extra bleed air line to cool the area between turb wheel and spider mounting flange , I've sorta worked out whats needed and have the job half completed , then a few supports for the plumbing and I can tick off another job...........not too many left :-)

Once I've finished with the 12/118 and this freepower stage, maybe next year , I might turn my attentions to researching how to construct a simple gearbox for us guys to make/use, ~6:1 ratio and made to mount a 4th stage wheel on the input and a bike chain on the output, duty time of 30 seconds to a minute , just long enough for a mile run , no fancy helical gears , plain spur gears and live with the "howl"..............gearboxes have been us DIY'ers worst nightmare , its time it was sorted out :-)

Cheers
John

[turboron]

John, I am still trying to visualize your design. Did you remove the 4th wheel shroud from the NGV? Did you include a replacement 4th stage shroud in your housing? What was the logic behind this design change?

Thanks, Ron

[turboron]

John, see my previous post on your NGV design.

Regarding the need for a gearbox you said: "Once I've finished with the 12/118 and this freepower stage, maybe next year , I might turn my attentions to researching how to construct a simple gearbox for us guys to make/use, ~6:1 ratio and made to mount a 4th stage wheel on the input and a bike chain on the output, duty time of 30 seconds to a minute , just long enough for a mile run , no fancy helical gears , plain spur gears and live with the "howl"..............gearboxes have been us DIY'ers worst nightmare , its time it was sorted out :-)

Cheers
John"


This sounds like a combined gearbox/power turbine design. I am looking forward to your design based on your "lessons learned".

Thanks, Ron

[racket]

Hi Ron

Yep , I removed the 4th stage wheels shroud from the NGV because it allowed me to mount the NGV without concerns for concentricity with the wheel .

The wheel runs within the mount for the NGV ibb.co/mFZ9wK , the mount has been machined concentric to the gearbox input shaft .

As for a rethink on the gearbox , it was sparked by the starter motor problem I had a week or so back when the starter solenoid fused together and it was running at full no load speeds , now the no load speed of the armature is ~20,000 but the stepup gearing of ~3:1 meant that the output shaft would/could have been doing ~60,000 rpm , which its standard ball bearings coped with for the few minutes it took me to find tools to disconnect the battery terminal, and the starter gearbox doesn't appear to have been adversely affected by its experience .

Now my thinking is towards a similar crude gearbox as I made for the starter, maybe a small car starter ring gear supported in a couple of sealed bearings on the output shaft , with a pinion shaft assembly that can be screwed to the main box, gear noise isn't an issue for us , as long as the teeth are strong enough the gearbox should be OK for our very limited usages.

It needs to be lightweight , relatively cheap to make from readily available bits , with minimal "precision" required.............piece of cake :-)

Cheers
John

[turboron]

John, I had a similar idea a few years ago. I was even going to use the car's bell housing.

Since then I discovered and am using a Briggs and Stratton gearbox originally used for roto-tillers etc. It is now used for racing in entry level racing karts. Honda has a similar unit. It has the pinon on the B&S crankshaft which runs inside an external ring gear. The gears are spur gears. With this gear arrangement the input and output shafts have the same direction of rotation. It is a 6/1 gear reduction. I use a timing belt for the second stage similar to your chain approach. I buy the used gearboxes with sleeve bearings on ebay for cheap. A new racing gearbox with ball bearings is about $500. I cut the pinon off the crankshaft, bore it and mount it directly to the turbine shaft of a large turbocharger. The racing crankshaft is a forging.


Thanks, Ron

[racket]

Hi Ron

YEP , those b and s gearboxes are neat units , sorta like the small post hole digger boxes , I have a Noram gearbox www.noramclutch.com/reduction-gearboxes/ that I was going to try and use some years ago, but the arrangement of the gears inside isn't the best , so scrapped the idea , there just doesn't seem to be many gearboxes out there suitable for us to push 100+ HP through , I keep looking every now and then to see if anything new has come on the market .

Cheers
John

[Johansson]

The ATEK V160 gearbox I use seems to take the beating really good after I modified it with oil jet lubrication and ceramic bearings.

[racket]

Hi Anders

LOL......thats one very solid gearbox you have , but perhaps a tad heavy for a kart installation , I'd like a gearbox weighing <10 kgs and ~15 kgs with freepower bits fitted , I think its doable , just gotta find the right bits , ............heh heh , started pulling apart some old starter motors I have here , nice lightweight and hardened "pinion gears??"

Did find a nice Module 3 shaft and 13t gear here khkgears.net/pdf/ssgs.pdf , the 30.2 mm shaft could be ground down a tad to slip through the 4th stage wheel bore ;-)

Cheers
John

[turboron]

John, B&S has a publication on their Animal Racing Engine and Gearbox. It shows that the engine is rated for 7.5 HP and 10 ft-lbs of torque at 4000 Rpm. Since the 4000 rpm is the pinon input speed we can ratio the HP by the power turbine input speed. In other words HP at the same torque is (60,000/4000)7.5 = 112.5 HP assuming a 60,000 RPM power turbine speed.


Also, I saw a tuned Animal engine rated for 36 HP at 9500 RPM. Therefore, (60,000?9500)36 = 227 HP.


I realize there may be other issues using this gearbox to these power levels. However, It may be a way to upgrade the design to our needs. Remember "Grab it and use it".


Thanks, Ron

[racket]

Hi Ron

It'd certainly be a viable gearbox for up to 100 HP , pinion RPM would be ~45,000 for the required mass flow , but for our larger engines the freepower RPM is down ~30,000 due to the diameter of the wheel required to pas the mass flow .

I'll checkout the info on the Animal Engine , thanks for that :-)

Cheers
John

[turboron]

John, could you share your rules of thumb for horsepower and rpm to get the 100 hp at 45,000 rpm. For aircraft engines of the 50's I use 100 horsepower per lb/sec of airflow.

Thanks, Ron