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Gearbox recall

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Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Thu Mar 06, 2008 7:57 am Post subject: Gearbox recall

Hi All, 



If any of you need your gearbox done under the Rotax recall, I am in Tucson Az. and based out of Ryan Airfield. No cost to you if you fly in and only shipping if you send it to me. Shipping is cheap. If you fly in I have a 2.5 hr. turn around and your on your way. If you ship it I have a 1 day turn around. I am an authorized and newly certified Rotax service center under their new certification program with 7 years of Rotax experience. Let me know. I have a number of gearboxes coming in so let me know so I can make sure I have enough gearboxes on hand. 

By the end of May I will be a full blown one stop shop for all your needs. Inspections, service (airframe and engine, dynamic prop balancing, ect..) I'm quick and very thorough. I specialize in LSA's and Rotax 912's, but will do experimental, too. I have a Flight Design CT myself and have many happy clients. 

If you have never had your prop checked for blade pitch you should and I very highly recommend a dynamic balance as most LSA are out of balance. If you prop needs adjusting we can do that in short order. Hopefully your WOT rpm is around 5500rpm. You don't see many props from the MFG in balance or that has some time on it and this can be attributed to a number of reasons. I started doing them because I found my CT was out and have seen most other LSA's out of balance and finding someone to do a good dynamic balance is a challange. It is good to do for the health of your engine and components. If you can feel it in the stick it is way out and most times you can't feel it at all, but it is still out of balance. 

You can always find me or my articles on the ctflyer.com website or on the Matronics Rotax engine web site. 



email: ssadiver1(at)yahoo.com

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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

vgstol(at)bigpond.net.au
Guest

Posted: Thu Mar 06, 2008 12:46 pm Post subject: Gearbox recall

Roger,



<....Hopefully your WOT rpm is around 5500rpm....>



I thought Rotax recommends 5800rpm.....  Please comment......



JG

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Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Thu Mar 06, 2008 2:19 pm Post subject: Re: Gearbox recall

Hi JG,



You can run the Rotax 912uls between 5500-5800 rpm for 5 minutes. The 5 minutes only part should tell you something. If you do not have to run it up over 5500 rpm for a specific reason then why would you want the extra wear and tear. If you have to have the extra rpm/hp then it's there, but it's much better on the system if you don't have to. That's why they give you the 5500 max continuous spec. The majority of people I know use the 5500 rpm for their WOT. With a ground adjustable prop or a fixed pitch you are trying to get it set for the best balance of speed, climb, fuel and over all performance as you can. 5500rpm pretty much meets this need. We're just trying to find a happy median for the aircraft and engine combination.

I'm not saying you can't run it over 5500, but if you don't need to????

In all of my Rotax classes over the years 5500 WOT has been the benchmark and then a nice cruise rpm of 4900-5100.

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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

vgstol(at)bigpond.net.au
Guest

Posted: Thu Mar 06, 2008 5:22 pm Post subject: Gearbox recall

I'm still a bit unsure about this engine loading...  I've always set  up by the book for 5800 WOT, and cruise at around 5000.  If the prop  is pitched for 5500 WOT then I can maintain the same cruise speed with  lower rpm.  But of course the same cruise speed requires the same  power output, so the engine is running at a higher torque to produce  that same output.  Nothing is for free here.....

  

 5500 for max continuous only applies if WOT is 5800.

 If WOT is 5500 then what should max continuous be??

 For the same % of full power, that would be maybe 5200??  In  which case cruising at 5100 is getting pretty near max continuous.....  I'm  not wanting to run anywhere near max continuous.

  

 I know some who do prefer to pitch up courser so that they are able to  cruise at lower rpm, but thought that this was not advisable....

  

 So do the Rotax classes indicate that it's preferable to set up for 5500  rather than 5800 WOT??

  

 JG  

  

  

  

  

 [quote]   ---

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Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Thu Mar 06, 2008 9:40 pm Post subject: Re: Gearbox recall

Hi JG,



Just so you understand. 5800rpm is the max rpm for that engine anytime, period, regardless of prop pitch. Everything is then figured from there. 5500 WOT is the max continuous rpm anytime, period, regardless of prop pitch. These numbers do not depend on the prop pitch, but are absolute per the engine specs. So no matter what the prop pitch is set to 5800 is the absolute max and 5500 can be run all day if you wanted to.

If you set the prop pitch to achieve 5500rpm WOT (wide open throttle) when flying straight and level then you are good to go. With ground adjustable or fixed pitched props we try to achieve a balance of our flight characteristics and engine performance verses wear and tear. 



Balance is the key here.



If you have your prop set to achieve 5800 rpm you will have killer climb, but suffer in the fuel economy and cruise speed. At the 5800 prop pitch setting you will have to fly higher rpms and more throttle (fuel) to keep the speed you want because the prop pitch is set too flat.  If you fly high altitude let's say over 7k' all the time then you will be able to develop a little more rpm and hp at high altitudes with a prop pitch set for 5800 verses 5500 WOT. If you have your prop set for 5500 WOT then you will still climb well, but you can now cruise at 5000rpm at a faster speed and at a reduced throttle setting which equates into better fuel economy.

You can go the other way and have the prop pitch set for 5100 WOT and have poor performance balance and you are lugging this engine, it is over propped. It was set to run and is happier at 4800-5200 rpm cruise at with a WOT of 5500.



The manual gives the 912's low and high specs, but does a poor job of where it should be set to be happy for its life span. They do teach these things in the Rotax classes. While we are on the subject of rpm settings the idle setting for the 912uls should be at 1800 give or take a few rpm. The 912 80hp only has a 9:1 compression while our 912ULS engines are 10.5:1 and this higher rpm cause real wear and tear at low idle rpms. It is better to also warm your engine up at 2000-2400 rpm. It runs smoother there and while it warms up has less vibration and gearbox wear. At this idle rpm setting you are not loading the engine enough just sitting there to be of concern. Right out of the Rotax classes.

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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Thu Mar 06, 2008 9:44 pm Post subject: Re: Gearbox recall

Don't beat your gearbox up.

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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

notsew_evets(at)frontiern
Guest

Posted: Fri Mar 07, 2008 7:15 am Post subject: Gearbox recall

Just slightly butting in here but,,

I had a Rotax years ago.  Got rid of the thing before anything happened and 

thats a totally different story.  I had the three to one (C) gear box and 

the RPMs were in the 7200 to 7800 range.  I pushed the engine hard because 

of the aerobatic preformances that I was involved in...

Anyway,  I dont get the 5800 max RPM statement.  If its 5800 and your using 

a 3/1 isnt that 1933 0n the prop ?

1933 doesnt seem to be efficient with most aircraft propellers.....

Educamate me please..



SW

---

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jpspencer(at)cableone.net
Guest

Posted: Fri Mar 07, 2008 10:44 am Post subject: Gearbox Recall

Roger

 Good to know we have another engine man around.  Thanks.

 I have been struggling a little with this 5500WOT  business but then I struggle with most everything anymore. I setup my  701/912ULS like JG-for 5800 WOT, straight and level(I figure that's where  it makes about 100 horses and since I paid for them I like to use them...or at  least be able to get to them if I need/want to) for maximim takeoff /climb  performance and minimum idle thrust, and I use firewall power for all takeoffs  and initial climb, honoring the 5 minute limit. I generally cruise at 5000 rpm  as you recommended. Since setting the prop for 5800 WOT s/l I have done some  airframe cleanup and the thing will blow right thru the very low airframe  redline before getting wound out to 5800. I have thought about putting some more  pitch in the prop to slow the motor down but the plane is already running  too fast unless powered way down which is my question for you...at what rpm  should we consider the engine to be lugged down?

 Your premise of "balance"(compromise) I agree is  normally what we strive for. The 701 however is such a unique little beast that  in my thinking it doesn't really apply, as it would to a 601, for instance. I  wouldn't want to give up any short field capability for the sake of balance(or  engine life-as long as it'e operated IAW the manual) cause that's what the  701 is all about.

 Thanks for your info.

 Best,

 Joe

  

  

  

   [quote][b]

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leo(at)zuehlfield.com
Guest

Posted: Fri Mar 07, 2008 12:11 pm Post subject: Gearbox recall

Steve, I have a 912UL:  Rotax Operator's Manual says 5800 RPM Red Line 

for 5 minutes max at takeoff.  5500 max. continuous cruise.  Gearbox is 

2.273:1 or 5800 engine RPM equals 2552 prop RPM and 5500 engine RPM 

equals 2420 prop RPM.  (I have a 68" 2 blade electric in-flight 

adjustable Ivoprop.)



Do not archive



-- 

Leo Gates

N601Z - CH601hds TDO

Rotax 912UL

steve wrote:

 	  Quote: 	
		   



 Just slightly butting in here but,,

 I had a Rotax years ago.  Got rid of the thing before anything 

 happened and thats a totally different story.  I had the three to one 

 (C) gear box and the RPMs were in the 7200 to 7800 range.  I pushed 

 the engine hard because of the aerobatic preformances that I was 

 involved in...

 Anyway,  I dont get the 5800 max RPM statement.  If its 5800 and your 

 using a 3/1 isnt that 1933 0n the prop ?

 1933 doesnt seem to be efficient with most aircraft propellers.....

 Educamate me please..

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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