Rotax Parts Supply Problems

[danny_galaga]

58 minutes ago, Blueadventures said:

Can you use a size from the ones that Atec or Bushcat use.  The brand they use seem to hold up in use.  Just buy the size you need.   We need in use R&D feedback from you and others.

Agree wondered why cannot buy through his ATEC dealership connections.

I did post the part numbers for the coolers Bushcat uses elsewhere. Setrab is the manufacturer. They make oil coolers for performance vehicles etc. Bushcat use them for the radiator too.

[BrendAn]

11 hours ago, Philster2001 said:

Try getting water hoses from Floods - been waiting 3 months for 5-yr replacement hoses, Floods say they have over 500M on order from Austria with no estimate of delivery timeframe!

is that the 17.5 mm hose for a 912

[Blueadventures]

13 minutes ago, BrendAn said:

is that the 17.5 mm hose for a 912

17mm I believe is the size.

[onetrack]

I heard BrendAn has a big roll of 17mm hose he's been trying to quit, but now his price has just doubled.  

[skippydiesel]

2 hours ago, danny_galaga said:

I did post the part numbers for the coolers Bushcat uses elsewhere. Setrab is the manufacturer. They make oil coolers for performance vehicles etc. Bushcat use them for the radiator too.

Hi Danny,  Setrab are a well known manufacturer - any chance you could repeat that part number?

[danny_galaga]

This is to suit Bushcat. But I guess would get you in the ballpark. I don't know if it's as simple as going by surface area. For instance, is the  surface area of 100 the same efficiency if it's 5x20 as 10x10? Note the Bushcat has two oil coolers the same size.

 

Oil coolers:

Manufactured by setrab

Part no. 50-110-7612 (Setrab Oil Cooler 210mm 10 row M22 female. Setrab part number 50-110-7612.) X 2. One has the brackets cut off.

Radiator:

Manufactured by setrab

Part no. 50-925-7612

[skippydiesel]

25 minutes ago, danny_galaga said:

This is to suit Bushcat. But I guess would get you in the ballpark. I don't know if it's as simple as going by surface area. For instance, is the  surface area of 100 the same efficiency if it's 5x20 as 10x10? Note the Bushcat has two oil coolers the same size.

 

Oil coolers:

Manufactured by setrab

Part no. 50-110-7612 (Setrab Oil Cooler 210mm 10 row M22 female. Setrab part number 50-110-7612.) X 2. One has the brackets cut off.

Radiator:

Manufactured by setrab

Part no. 50-925-7612

Thanks Danny,

 

As I understand it, surface area is the main factor (number of tubes) influenced by depth, fin density, design and air flow. How the factors  interrelate is fairly complex (beyond me). To try & make some sense of it all, I first look at the frontal area (square) and then multiply the depth (cube) but I know there is more too it than just that.  

[skippydiesel]

Setrab 50-925-7612  Features and Benefits

• 14.5" wide core (310mm)
• 25 rows or 7.5" (190.5mm) core height
• Made in Sweden

Rotax Extra Large B 218 x C 175 x D 40mm =15260003 

Setrab 13 Row (tubes?) B 368 x C 102 x D 51mm =19143363

I have guessed that the Rotax offering has about 13 tubes

Setrab equivalent has significantly diffrent dimensions - what might be the performance implications?

Edited June 18, 2023 by skippydiesel

[skippydiesel]

Further to the above - I think these are what are called Setrab Series 9 Oil Coolers

[danny_galaga]

Bear in mind the Bushcat jobbies take into account a fairly low cruise speed and built for hot weather conditions. So guess it could be smaller in a faster aircraft. I've forgotten, were you building a Zenith 701? 

Edited June 19, 2023 by danny_galaga

[skippydiesel]

Space availabity aside and that cross tubes (Rows) have the same ID/OD & internal structure - is it best to have Short OR Long cross tubes??

Edited June 19, 2023 by skippydiesel

[skippydiesel]

6 minutes ago, danny_galaga said:

Bear in mind the Bushcat jobbies take into account a fairly low cruise speed and built for hot weather conditions. So guess it could be smaller in a faster aircraft. I've forgotten, were you building a Zenith 701? 

Sonex/Rotax 912ULS, early days but high speed cruse figures are about 140 -150Kn TAS HOWEVER the oil cooler must also perform adequately on the ground

Edited June 19, 2023 by skippydiesel

[facthunter]

Except  for the take off run you're only using idle power on the ground. Taxiing for long distances downwind can cause issues  or when you've used high power on the approach.  Nev

[danny_galaga]

I'll see if I can get the approximate dimensions off the Tecnam I hire. It's a faster plane, still nowhere near your speeds but if it's something smaller than what I have you will know for sure it's adequate 

[IBob]

Can I belatedly ask why you are going for the extra large oil cooler, Skippy?

 

[skippydiesel]

2 hours ago, IBob said:

Can I belatedly ask why you are going for the extra large oil cooler, Skippy?

 

Yes you may - When test flying started, we had runaway high oil  temps - we were always having to go into a shallow desent, to get the temps below 120C .

 

To may adjustments to list later, we now can reliably keep temps below 112C in cruise and it takes much longer to get there - still way to high.

 

Lower temps up to 104C can be maintained in cruise IF I keep my prop in in Climb Mode ie don't switch my CS to Cruise Mode. This suggests to me,  that the load, imposed by Cruise Mode, is resulting in higher oil temps.

 

My target temp is Max 95C in high speed cruise (Cruise Mode). 

 

Existing oil cooler is Rotax Large.

 

Sonex now in the workshop - there will be relocation of  both heat exchangers, which should result in better air flow through both BUT I feel (very scientific) that the existing oil cooler just does "cut the mustard".

 

[IBob]

Thanks for that Skippy. A couple more questions:
What RPM do you cruise at if in cruise mode?
What RPM do you get if you give it full throttle in cruise mode?

You may have already covered all this earlier in the thread or posts, if so, apologies.
It's probably I also need a lesson on CS props???

[skippydiesel]

29 minutes ago, IBob said:

Thanks for that Skippy. A couple more questions:
What RPM do you cruise at if in cruise mode?
What RPM do you get if you give it full throttle in cruise mode?

You may have already covered all this earlier in the thread or posts, if so, apologies.
It's probably I also need a lesson on CS props???

No problemo! -  Cruise Mode, I try for anywhere between 5100 - 5450 rpm (WOT) MAP 25 - 27.  Usually 5200 rpm MAP 26.

 

The Airmaster CS is pre set for WOT 5450rpm - I can go to Manual Mode and go to 5500 rpm,  but I don't. I like the small 50 rpm "buffer" by staying at 5450 rpm

 

If I stay in Climb Mode I operate between 5200 - 5350 rpm

[RFguy]

Rotax specific : just be careful when choosing an oil cooler to not go too long and skinny (long in tube length) 'cause the suction tension gets too high (pressure drop) .

With a new install, be sure to  check the suction tension PER ROTAX MANUAL to be sure you are inside the max suck, otherwise your engine will starve.

Edited June 19, 2023 by RFguy

[Thruster88]

1 hour ago, skippydiesel said:

Yes you may - When test flying started, we had runaway high oil  temps - we were always having to go into a shallow desent, to get the temps below 120C .

 

To may adjustments to list later, we now can reliably keep temps below 112C in cruise and it takes much longer to get there - still way to high.

 

Lower temps up to 104C can be maintained in cruise IF I keep my prop in in Climb Mode ie don't switch my CS to Cruise Mode. This suggests to me,  that the load, imposed by Cruise Mode, is resulting in higher oil temps.

 

My target temp is Max 95C in high speed cruise (Cruise Mode). 

 

Existing oil cooler is Rotax Large.

 

Sonex now in the workshop - there will be relocation of  both heat exchangers, which should result in better air flow through both BUT I feel (very scientific) that the existing oil cooler just does "cut the mustard".

 

If I recall correctly there was some discussion about the original location of the heat exchanges and why that might be problematic.  

[skippydiesel]

1 hour ago, RFguy said:

Rotax specific : just be careful when choosing an oil cooler to not go too long and skinny (long in tube length) 'cause the suction tension gets too high (pressure drop) .

With a new install, be sure to  check the suction tension PER ROTAX MANUAL to be sure you are inside the max suck, otherwise your engine will starve.

Agreed - unfortunately most Oil Cooler specifications are all about positive pressure. I don't recall one that gave a  negative pressure specification.

 

This is why I am so intersted in other Rotax drivers experience with after market coolers - it may be the only way to assess a cooler is fit for (Rotax) purpose.

[RFguy]

well pressure drop is about flow, so, except at the margins, there is little /  no difference with suck or blow , spits or swallows. use the pressure drop/flow number.

Edited June 19, 2023 by RFguy

[skippydiesel]

1 hour ago, Thruster88 said:

If I recall correctly there was some discussion about the original location of the heat exchanges and why that might be problematic.  

 Yes - I am the second builder. The first has  conducted the build (from plans) with extraordinary attention to detail & quality. This is an "Experimental" category and in this case one of the the experiments was to have an aft mounted Coolant Radiator, being exclusively fed by air from within the cowling. The Coolant side of the equation works well, in the air, not so good at all on the ground BUT because it restricts the flow of exit air, it pressurises the cowling, such that it inhibits the performance of the Oil Cooler.

 

The above arrangement will be soon be changed, with the Radiator relocating to a more conventional forward position. This will allow for unrestricted exit air flow,  hopefully reducing under cowl pressure to negative. I have yet to decide on a location for the Oil Cooler but will strive for a pressure differential from High to Low across its fins/tubes.

 

 

[danny_galaga]

2 hours ago, RFguy said:

Rotax specific : just be careful when choosing an oil cooler to not go too long and skinny (long in tube length) 'cause the suction tension gets too high (pressure drop) .

With a new install, be sure to  check the suction tension PER ROTAX MANUAL to be sure you are inside the max suck, otherwise your engine will starve.

And if you get it wrong, and the engine blows up,  there will be max suck alright 😄

 

On a serious note, the Bushcat has its two oil coolers in different positions- one below the propeller, and one above. Perhaps if you used the same coolers you could have them in different positions too, thus potentially reducing the impact of poor cooling when taxiing? One could be in the cowl, one could be say under the wing a la Spitfire.

[facthunter]

Flow is ONE thing. It's proportional to pressure difference . Operating at below ambient pressure is something else requiring other considerations structurally.   Nev