KJ66 Conversies

first test i reach 98k ..trust 11,5kg 487°c
then compressor fail....

the photo show different type of aluminium wheel

 

Ooops.....:schrik:

I assume thats a cast failure?? 98K is very low, did you experience some surge just before? Engine running cool and good before failure. Hope nothing more is damaged.

Rgds,
Gerald

 

first accelleration ramp was very slow, no hot spot and other
no damage ...only big imbalance after failure
the compressor debris touched the diffuser under compressor...but no damage
only bearing to change.. (now is noisy)

i see that last compressor is made in dark aluminium look instead light about previous one

the egt was stable from idle to 98k from 450° to 550° in acceleration

 

today another test ext. temp. 2°c

 

firts test video... conservative rpm 110k


I_Jq9bnODao[/media] First run - max110k - YouTube

 

kj 66

very beautiful.
but i hear your bearings a little bit.
That,s nog good for the lifetime of your bearings

.

 

many thx

there was noisy bearing used in other test engine... need to change with news when engine will be ok... no imbalance when running

 

working on another two diffusors

 

frees machine

Mooi Hobby bankje

Nice hobby tool

 

one of 5x machine of factory
the diffuser is made simply in 3x mode

 

jetflydemoteam one of 5x machine of factory
the diffuser is made simply in 3x mode


Why, If you can use 5x?

 

because other machines are busy
this geometry is simply to made ...3x is ok...to work (only 2 tools used)
if the diffusor should be 2 stage design 5x machine is very useful

 

Dear Gerald,

i'm in my way to manufacture my jet and i need your help to buy bearing and turbine 85 mm

 

Hi Ahmed, I use these turbine wheels: JETMAX | PRODUCTS | Turbine Wheels

and these ballbearings:
GRW - high precision ball bearings | Ball Bearings for model building

Best regards,
Gerald

 

I am also building some UT-160's I thought it was easier to make 10 at the same time... Are there any mods I should know before I build the chambers?

 

hello...nice work... in my opinion ut160 must to be modified in the diffusor and CC
like FREMA indications

 

hello,
How could i choose the best impeller Diameter corresponded with tubine diameter ??
and what is the parameters changes with the diameter of both ?

thanks

 

Hi Ahmed, I don't do any calculations, mostly trial and error....

That said, diameters of both wheels should be same in most cases and works fine. However, when having a good engine with efficient NGV/turbine combination we can increase impeller diameter to max 106% compared to turbine diameter. This wil give some increase in power for the same engine diameter/weight. (With different reaction turbine we can go even further but that only gives more torque to the shaft, no more direct power, good for turboprop engines)

Here some comparison for a typical 80N engine with 66mm turbine wheel:
66mm = 84N thrust @ 120K rpm
68mm = 96N
70mm = 108N

70mm turbine wheel:
70mm compressor 140N thrust @ 120K rpm
72mm = 160N
74mm = 180N

Data above gained via tests, not calculated.

Hope this helps?

Best regards,
Gerald