Mailing List flyrotary@lancaironline.net Message #29964
From: rijakits <rijakits@cwpanama.net>
Subject: Re: [FlyRotary] Torque and torque sequence
Date: Sun, 5 Feb 2006 12:18:12 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
 
----- Original Message -----
From: Al Gietzen
Sent: Sunday, February 05, 2006 11:32 AM
Subject: [FlyRotary] Torque and torque sequence

----- Original Message -----

Sent: Saturday, February 04, 2006 6:28 PM

Subject: [FlyRotary] Re: Atkins errors

 

In a message dated 2/4/2006 5:56:30 PM Eastern Standard Time, ALVentures@cox.net writes:

A couple of questions: Why are two of the bolts larger?  What is the torque spec on these bolts for the 20B?  I seem to recall 26-28 ft-lbs.  I can’t get a torque wrench on the bolts without removing the re-drive, engine mount and flywheel, but I have a pretty well calibrated arm.

 

Al

When you add torque to those bolts, the bolts closest to them will go under torque.

 

So go through the whole torque sequence several times if at all possible. This has been the case on every engine I have built.

 

Lynn E. Hanover

 

 

 

I don't havea Mazda Manual, but generally in a case like this there are 2 ways to tighten the bolts correctly:

 

a) Tighten 2 opposite bolts until seated - then torque each to spec. All other bolts are tigthtened spreading out from the 2 torqued:

e.g. Torque the 2 big bolts then: 1st bolt to left of one big b. - 1st bolt to the left of the other big b. - 1st bolt to the right of the one big b. - 1st bolt to the right of the other big b. - 2nd bolt to the left...... you get the idea.

 

This way you have the pieces flat together on a "centerline" and "lay" the rest down on each side of this centerline - spreading it out so that no "wrinkles" are created....

 

b) A stepped sequence is shown in a manual: mostly in cross pattern and something like 10 lb/18lb/26lb

 

 

Thomas;

I understand the niceties of torque sequence; but it would seem that is all out the window when the engine has been run about 6 hours, many cycles to full power, and a dozen or more temperature cycles to 200-210 F; all with the two large bolts loose.  As far as I know nothing untoward has happened, but how can I be sure?

 

Al

 

Al,

didn't intend to step on your engineering prowess, you are waaaay ahead of me in that department!

Just was pointing out what (little) I remember from Engineering school.

In your case, the only acceptable (...for me) way to go is, to remove the redrive, loosen all bolts and tighten them according to the manual.

In a (race)car you might get away with an "emergency"-thighten-up, but it is your a**  up in the air!!

Your engine was running well for a while now, so a complete tear-down seems excessive, but I believe wrong ( or none ...) torque-settings will show their ugly face in the long run. Better make sure everything is right and tight.

I understand that it is definitely NOT your fault, but your engine builders - you might believe these guys put a little more extra care into assembling an AC engine - manual on the job, step by step list to hook off items, after-assembly check list, etc.

 

In your case torques on bolts don't mean anything at this time. "Niceties of torque sequence" applies IF DONE (right) - obviously on your engine no one cared enough to check torque, let alone sequence.

Doesn't shine to well on a supposedly reputable shop....

 

Enough ranting, back lurking!

 

Thomas J.

 

 

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