"Fat Boy" 12/118 thrust engine

[racket]

Hi Anders

Yeh , hopefully I can come up with a solution , LOL.......a 10 Kw starter that turns 30,000 rpm would be ideal , now where can I find one :-)

Cheers
John

[racket]

Hi Mark

I was talking to Andrew the other day when I couldn't remember what starter bits I'd originally sent down with the 10/98 engine and he mentioned you guys had been "playing" .

The 12/118 build will need to be put on hold for the winter whilst I get back to work on the house painting , but I'll be doing some research and collecting bits during that time and possibly get something cobbled together when I have a day off .

I've got a feeling the 10/98 starter setup Andrew has made with the brushless motor might do the job, I might have a long chat with about it :-)

Cheers
John

[smithy1]

Bugga..! I would've thought 24v through that starter would easily get it up over the hump If the starter is getting hot.... Is the starter itself in good nick?....might have a poorly commutator/brushes or something silly like that...

Do you have any way of using a blower or air impingement John.??

Cheers,
Smithy.

[racket]

Hi Smithy

Yep , I was hopeful too , but reality stepped in to give me a hard time.

What size is the starter on the C20 ??

My biggest problem at low rpm during a spoolup might be component efficiencies , if the comp is only working at 60% and turb down at 70% it might need a longer spoolup to get rpm up into more efficient regions of the map so that the dodgy turbine stage can cope .................the "hump" might be a tad bigger/longer with this engine , dunno really , all I can do is try a few diffenent things .

Currently the starter on 24 volts , 26 volts with freshly charged batteries, produces ~10,000 rpm , now this is I'm assuming at max power output from the starter ,taking into consideration rpm vs amps vs efficiencies etc etc , the starter had an ~4.something to 1 gear ratio , so output gear would be doing ~2,000 rpm normally in the automotive scenario , this sounds about "right" .

Now if the "sweet spot" for the starter is 10,000 rpm and I'd like 30,000 rpm , then I might need a 3:1 step up gearbox on the starter so that it keeps the rpm in the sweet spot .........thoughts??

High pressure air impingement as an addition is being considered just to get the engine over the hump once the electric starter starts to run out of power at high rpm .

LOL.....Lotsa things going on in my head at the moment :-)

Cheers
John

[enginewhisperer]

it might be possible to do a nice sliding coupling with a toothed belt or small chain drive to a larger starter motor mounted under the turbine engine?

Otherwise a longer starter shaft would allow the starter to be larger and mounted further from the engine.

I have various motors and gearboxes that might work for a step up drive - but would need to play with some numbers.


I also have a few different car starter motors that might have more power...



As Smithy said, what about a blower to begin with?

[dieselguy86]

Hi John,

Im an avid rc plane/heli/turbine enthusiast, electric stuff included. There is a motor available but it isnt cheap:Motor 
Some research could probably find a chinese clone for 1/4 the price probably. This motor would require 6 car batteries to power it and can hold 28,000 rpms. This being a brushless motor it will require a speed controller and an rc "servo tester" to command it.

probably more than what you want to deal with, but it is out there.

-Joe

[racket]

Hi Joe

Yep , I've looked at the big brushless ones but the kV is generally too low , I have a big brushless outrunner sitting in my shed but it needs a gearbox as well , if I can't get the auto starter to work I'll have to go brushless and bite the bullet and shell out some hard cash for a decent setup.

Cheers
John

[racket]

Hi Andrew

A blower would work probably but it'd have to be BIG , even bigger than Smithies one .

Blowers work good because they don't have a rpm limit , they keep providing power up to the point where the comp wheel wants more air than the blower can provide.

I'll have a good think over Easter :-)

Cheers
John

[smithy1]

Mar 23, 2016 18:30:08 GMT -5 enginewhisperer said:

it might be possible to do a nice sliding coupling with a toothed belt or small chain drive to a larger starter motor mounted under the turbine engine?

Now there's a good idea right there...! Good thinking Andrew..! Easy to "Gear up" via the belt pulleys or chain sprockets too.

Cheers,
Smithy.

[smithy1]

Hi John,
Just got a request to do a car show in Port Mac on Saturday May 7th....I might go up and have a look....bring the beast and missus with me.... and we might even drop in on an old friend who lives nearby..!

Cheers,
Smithy.

[racket]

Hi Smithy

That'd be nice :-)

Cheers
John

[racket]

Hi Guys

This graph explains it all :-(

Max rpm = minimal starter power



Gotta get a gearbox on the starter to keep rpm down

Cheers
John

[gtbph]

Hi John,

Sorry to hear it didn't start.
I think I would first try with a third battery.
Motors with magnets have a direct relation between the voltage and RPM, because when the rotor spins, it generates a voltage like a dynamo, that "cancels" the supply voltage. So if the motor spins fast enough, you can apply more voltage without burning the motor. But that's only true when the RPMs are not limited by it's power capacity, of course, and if it already gets hot now, maybe that's not a good idea. But maybe it could work if you give it 36 volts only after the engine has ignited.

Else you could try an AC motor with a winding on the stator, because these don't have an RPM limit, they just accelerate until the load slows them or until they self-destruct.
(The rotor also generates a voltage, but because the stator is connected in series with the rotor, this lowers the voltage across the stator winding, which in turn reduces the magnetic filed, an this finally reduces the generated voltage in the rotor. So there's no RPM limit. )

Cheers and good luck, Alain

[gidge348]

Mar 23, 2016 19:16:27 GMT -5 smithy1 said:

Mar 23, 2016 18:30:08 GMT -5 enginewhisperer said:

it might be possible to do a nice sliding coupling with a toothed belt or small chain drive to a larger starter motor mounted under the turbine engine?

Now there's a good idea right there...! Good thinking Andrew..! Easy to "Gear up" via the belt pulleys or chain sprockets too.

Cheers,
Smithy.

Agree..

Another option if you wanted to "gear up" and wanted a cheap starter power source may be to use one of these www.ebay.com.au/itm/6-Teeth-49cc-2-Stroke-Pull-Start-Engine-Motor-Mini-Dirt-Pocket-ATV-Quad-Bike-PIT-/261299127329?hash=item3cd6a44421:g:FkMAAOSwu4BV5jK2

Small, cheap, centrifugal clutch.

There is a precedent for using a 2 stroke starter motor in the ME262

Cheers
Ian...

[jetgran]

We used a 240volt router £29.00 from B & Q. Good for work shop testing