~35-70hp turboshaft for a Lemons car - brainstorm

[firegremlin]

Got one ordered just like that, should be here by Friday. I'll do a writeup on the gearbox once I pull it apart.

[finiteparts]

Just an FYI...the final gear ratio is made with the tiny drive gear on the torque convertor to the giant gear on the flywheel. Without the giant flywheel gear, I am not sure what the reduction will be.

[enginewhisperer]

Mar 10, 2024 22:46:32 GMT -5 finiteparts said:

Just an FYI...the final gear ratio is made with the tiny drive gear on the torque convertor to the giant gear on the flywheel. Without the giant flywheel gear, I am not sure what the reduction will be.

Hopefully it's enough that the next stage can be done with some available gears or even a chain reduction.

If it's driving into an existing car gearbox it might work ok just to use a low gear - even if the gearbox life span is a bit reduced due to high rpm.

[racket]

You probably need an overall gear ratio between freepower and car wheels of ~25:1

[firegremlin]

Stock overall ratios are: 17.73, 10.02, 6.87, 4.69

Tires are ~23".
If the primary reduction ratio is under 7, I won't need any further reduction to hit 100mph in top gear. That's the highest speed I can hope for, power-wise. If it's 5 or less, 3rd gear would be better.

For my gas generator, the turbine outlet would be smaller relative to compressor inlet than it would be for a "pure turbojet" build, correct? And am I looking to match volume flow of the stock diesel motor for the compressor size? As in, less mass given that power turbine's inlet temperature will be greater. I hope I'm thinking in the right direction here.

[racket]

Theres no difference between a DIY engine for a pure jet or a freepower , all the gas producer feels is backpressure, it doesn't differentiate .

Check through those Links provided for your numbers to workout the turbo size required, I'm pretty certain its all been worked out before .

[Jetman]

Found a video that shows what gear the HP841 gearbox drives on the DD15 engine: www.youtube.com/watch?v=l06ZkDgxAk4 It's at 3:10.

[richardm]

Watch from 05:20.. I dont think it will last long...https://www.youtube.com/watch?v=CfKi9UvyDnc

[racket]

That guy has no idea what he's doing :-(

I'd say he also cooked his gas producer .

NEVER run a freepower without load , overspeed very easily

The temps were too high before even accelerating to higher gasifier rpm , the gas producer turbo was probably too big , maybe tried using the standard truck combination of turbo and freepower without doing the maths , he forgot about the ability of the pistons to force the gases through the freepower at higher pressures than the DIY engine can produce, resulting in too much backpressure on the gas producer resulting in high temps and a wrecked engine .

Gotta do the maths

Cheers
John

[firegremlin]

So, on one hand, looking at that free-spinning free turbine - 100% confirmed that I'll need to reverse rotation direction.

On the other hand, that gear in the animation video, it's reasonably priced and has 106 teeth: www.vanderhaags.com/detailview.php?part=24651731

And the output gear on the turbine gearbox has 17 teeth.

That can be a 6.24 final drive, if you mate it to some sort of a diff. It might be the way to go - transverse turbine, direct drive, electric assist.

[richardm]

transverse turbine, direct drive electric assist.. Just my opinion but looks to me like a can of worms .
Maybe you could just use that Holset turbo compound to drive a generator and go all electric from there

[firegremlin]

It may seem easier, but that would be an entire Prius gearbox worth of motors, with inverter, plus controller, plus big battery - series hybrids snowball pretty quickly. Direct drive with a single, smaller electric motor would be much lighter and easier to build, I think.

[racket]

Have you looked at the build threads on here with freepower turbines to get some ideas ??

[richardm]

Going electric might not be that difficult Conversion its are sold On advantage is that you could still drive the car home after the turbine failed. And that will occur.

[firegremlin]

Mar 13, 2024 1:41:34 GMT -5 racket said:

Have you looked at the build threads on here with freepower turbines to get some ideas ??

Working on it, it's a lot of multi-hour reads. Give me a couple of weeks