Dave:

Can't argue economics either! :)

Spot on.

Hmmm, quality made mass produced heli's for everyone! (Well, those little ones in the toy store are grand, but not enough power, and they don't have enough room .... :) )

T'aint Natural

Re throttle chops(a few days back). In my experience ok to chop the throttle when simulating real engine failures with the following provisos:

1) Don't do it during the first 10 to 15 minutes of flight as the oil will not have warmed up and this can lead to carb icing

2) Correct handling of carb heat prior to throttle chop ie full CH

3) Not reccommended to do it too ofen as the engine is going from full power to idle and will cool rapidly leading to cracking problems

Further info. As a result of an accident, I investigated partial engine failure situations in full power climb, simulating stuck valve. Somewhat to my surprise, this led to almost as quick a rotor rpm rundown as in complete engine failure.

Speaking of throttle chops, here is something new.....

R44 - SERVICE BULLETIN #41


DATE: 01 August 2001

TO: All R44 Owners, Operators, and Service Centers

SUBJECT: Tail Rotor Rigging

ROTORCRAFT AFFECTED: R44 Helicopters

TIME OF COMPLIANCE: Within next 25 flight hours or by 15 September 2001,
whichever occurs first.

BACKGROUND: Inadvertent abrupt application of full left pedal by the student during
a simulated power failure could result in excessive flapping of the tail rotor and
possible tail rotor blade contact with the tailcone. To reduce the possibility of that
occurring, Safety Notice SN-27 Sudden Power Chops Can Be Deadly has been
reissued as a Safety Alert. In addition, this Service Bulletin requires re-rigging the
tail rotor to reduce maximum blade angle at the left pedal stop and also requires
installation of a harder teeter bumper.

To: rotormatic

Why wasn’t this discovered during the certification trial when full left and right pedal were used in accordance with the certification requirements.

Fossil:
May I add to your list...
4) Do it on somebody else's helicopter.
Lu: The reason that something that has never happened (but possibly might) was not discovered at the certification stage is because Frank Robinson is involved in a widespread international conspiracy involving the FAA, the NTSB, NASA, Bill Clinton, George Bush, Osama bin Laden, me, Nick Lappos and persons too numerous to mention to pass off this patently unsafe helicopter on a gullible public. Luckily we've got people around like you to spot the plot. Now go away.

The main reason I have not flown a Robinson product is that not one of the Robinson pilots (many of which are instructors) in my area have shown me that they can fly the helicopter safely and responsibly.

Safety lies in the hands of the pilot, regardless of the type of aircraft.

yxcapt :

With respect, I think you're looking in the wrong place, or you have EXTREMELY high standards (not such a bad thing ).

I flew in the US a few weeks ago with instructors I'd trust implicitly, and if you come to the UK, there's plenty here who can show you the limits of the machine in a predictable and safe manner.

For what it is worth, a close friend and excellent test pilot for Sikorsky left the company several years back to get closer to general aviation. He is an excellent engineer, and was a scrupulously safe test pilot (he regularly flew the XH-59A/S-69 ABC experimental aircraft). I flew with him hundreds of times. He started a helicopter flight school, using Robinsons, and is doing quite well.

Many of his students are engineers for Kaman and Sikorsky.

One can infer something about Robinson from this, I think. <img src="cool.gif" border="0">

Nr: I do have very high standards and I realize that not all R22/44 operators operate their equipment in the same fasion. Unfortunatly, from my experaince here, I can see why the Robinson has a controversial reputation.

Keep the RPM up!

Nick:

What is the name of his school? Where is he located?

Thanks

yxcapt,
email me for the specifics. I am sensitive about not being an advertising agent for him! :)

I learned to fly helicopters in a civilian school at the hands of serving British military pilots who were moonlighting from day jobs flying Pumas, Chinooks and other such hardware at RAF Odiham, outside London. Almost all of them looked askance at the R22 when they arrived, having heard the kind of negative stories which are often rehearsed in this forum, but soon grew to trust and even love the machine once they had experience of it.
I recently had an opportunity to take two Aerospatiale pilots, over here to demo the EC130, for flights in the R22. They were particularly surprised at the excellent correlation (governor out) and by the efficacy of the governor.
I don't know of a single accomplished helicopter pilot who has had his prejudices about the R22 reinforced by experience of the machine.

From article 'Designing Rotor Blades' by Martin Hollmann in Dec 2001 ~ Jan 2002 issue of Rotorcraft.

&gt;"Another not often known secret in rotor blade design is to incorporate a small amount of tip weight into the blades. In the Sportster blades I use a 2.6 lb steel rod. This tip weight does wonders.

It reduces the coning angle, which increases the performance of a helicopter or gyro.

It increases the inertia of the rotor for better autorotation. The early Robinson R22 helicopter did not have tip weights and pilots complained about poor autorotation (2 seconds to put down the collective for autorotation when the engine stopped) and high control sensitivity. I met Frank Robinson one day and told him about rotor tip weights and asked him why he did not use them on his little helicopter. He said that he simply did not think of it. Two weeks later a bulletin from the Robinson Helicopter Co. came out announcing that all R22 blades would be retrofitted with tip weights."&lt;

Tain't:
If 'fossil is who I think he is, then I can think of few better qualified to have investigated throttle chops as he did, which I suspect was in response to the need to find more about the cause of a tragic accident.
I agree with your observation of respect for the R22. I have flown a variety of helicopters from trainers through to CH47, including the R22. I think it is an excellent cost-effective machine: and I respect it. Not to do so invites the old adage: 'All aircraft bite fools'.
Low inertia rotor systems require careful handling and AFM limits are just that. Beyond that, all pilots have personal limits. Ignorance of these AFM and personal limits sometimes has very sad consequences.
I think I have said before on a previous R22 thread that it is inevitable that a machine as 'accessible' as the R22 will have a highish accident rate, since many of those flying it will be relatively inexperienced, or private pilots who may not fly as often as they would like to.
Going back to the starting point of the thread, it's an interesting and perhaps encouraging statistic that the R22 accident rate looks quite favourable.

(Edit for spelling and to say that yes, I can think of better ways to spend Christmas Day than ppruning, but some of us are at work! Happy Christmas to you all.)

[ 25 December 2001: Message edited by: Multp ]</p>

T'aint natural,

Actually, there are some of us ex-mil beefers about who don't like the R-22. I was given the opportunity of instructing on it (moonlighting), some 15 years ago. I had no pre-conceived ideas, no axe to grind and had something to gain by flying it (at the time I was very keen to earn extra cash because of our 3 young children and a 14% mortgage rate).

However, having done a walkround and flown the aircraft once, I politely declined the job offer.
I have looked at the aircraft a few times since but I still agree with Frank Robinson, who said some years back that it wasn't conceived as a training aircraft.

Just my opinion and my choice. <img src="wink.gif" border="0">

What Shy Torque stated about Frank Robinson’s comment about the R-22 not being conceived as a trainer is true yet his firm lays claim to having the highest unit sales for a given helicopter in the world. Most likely 90% of Robinson’s sales are to training facilities. Tell me if there is something wrong with this picture.

Merry Christmas and a Happy and safe New Year from Quebec.

I learned in a Bell 47 (OH-13E), which was not conceived as a trainer.

Is there any helicopter made that was conceived as a trainer? Even the US Army primary trainer is a re-treaded observation helicopter.

It is my assumption that the H-13 which was a derivative of the original Bell 47 which was the first US Certified helicopter also carried as a part of its’ certification an application as a trainer. Even if this were not true when the H-13 entered US Military service it was classified as a utility aircraft which also qualifies it in the trainer roll. If the H-13 never existed the US Army would not have a trainer available until they purchased the Hughes 269 or they would have used the H-23 which they most likely did.

Uh-ho.

Looks like I started something.

Nick, you are probably correct. I trained in the Whirlwind HAR-10, an RAF variant of the S-55 which definitely wasn't conceived as a trainer - it was an ex SAR aircraft, as I am sure you will recall.

It was unstabilised but it was forgiving (we were required to fly solo engine-offs to the ground as basic students), and it was a big aircraft with a lot of metal between the ground and one's personal parts. The Nr control was not a problem either, 80 kts and 190 Nr rings a bell for a range auto (in that configuration you could see the individual blades going round from inside). It made a very good basic trainer. It could also be used for USLs and winching, all of which was included in the basic course.

I was unhappy with the R22 because it seemed very small and delicate in comparison to the other helicopters I had operated, even down to the Gazelle which I had instructed on and particularly so in relation to the Wessex, Puma, Huey, Hughes 500 etc that I also had experience of by then.

During the early to mid 1980s the R22 had a dubious reputation in UK. There had been a lot of sudden engine failures and coupled with the low rotor inertia there had been problems....

When I got close to one and flew it I realised how lightly built it was, alarm bells rang for me so I stayed out after one flight. Put bluntly, I don't like to fly anything where I sense a risk of using my ar$e as an undercarriage.

I am very much aware of the improvements in the engine governor, engine reliability, and rotor inertia etc but I still don't want to fly one again.

It does have to be said that some very experienced pilots have had accidents in this type, some of them not satisfacorily explained.

I can't comment on the line that Lu Z follows about incorrect rigging and excess flapping with sideslip etc; my decision was already made long ago for these other reasons.

Frank R was quoted in an interview some years back with one of the rotary magazines as saying he had intended the aircraft to be used like a car by experienced pilots. I had to agree. However, it was inevitable that flying training outfits would use it because of the low costs.

Undeniably, the safety record of this type has improved markedly over the last few years, but it's still not for me.

I woud just like to make it quite clear that I have nothing personal against this manufacturer, As I said on a previous thread, most aircraft have had serious problems at some stage or other.

I will run the following for several days in order to solicit comments from contributors to this forum and then I will remove it as it takes a lot of memory.

[Article deleted]


No, you won't Lu.
Anyone interested in reading this 'scare story' by some reporter can email you for the reference.

You've had unlimited space on many occasions to air your anti-Robinson obsession /conspiracy theories on Rotorheads. We even got Frank Robinson to post on Rotorheads answering your allegations. His replies seemed to satisfy most people, although not you as I recall.

Please:
* Keep your posts to a reasonable length
* Avoid saying (or repeating) anything which might be defamatory.

Edited by Heliport
Moderator

[ 26 December 2001: Message edited by: Heliport ]</p>

Before the Robinson, what percentage of training ships ... er, strike that, ships used in training had low-inertia rotor systems? (People will buy what they want Lu, no one has forced those training facilities to buy a Robbie. Indeed you should be asking yourself why they do, even at increased insurance rates ... Market driven economy here, they want it 'cause they like it)

I ask because it stands to reason that all who were flying higher inertia systems came to the robbie, and without the proper training to respond in a timely manner to certain flight conditions, were killing themselves.

Sure, the Robbie requires one to be sharp, the arguement possibly being that you have to be sharper than in something else (arguement in JH about the Hughes 300) to stay on top of it.

Yxcapt, if one is trained properly, the bird is plenty of fun! I'm sorry to hear that perhaps you were not with some who might have been.

[ 26 December 2001: Message edited by: RW-1 ]</p>

Frank Robinson once told me he had conceived the R22 over a period in which the US was training tens of thousands of helicopter pilots for Vietnam, and his attempts to interest his various employers in the small personal helicopter had been driven by the expectation that these people would need personal helicopters when they were demobilised.
The big manufacturers, however, had been bitten that way before. Sikorsky, Piasecki, Hiller and Bell all expected a "helicopter in every garage" scenario to develop after the Second World War, only to be sadly disillusioned.
Some people have claimed that Robinson only makes this claim to forestall potential liability; I think, however, that there is truth in it.
As to the claim that Robinson didn't put tipweights in his early machines because he "never thought of it," believe it if you want. He spent every waking moment thinking about the helicopter from 1957 to the day it flew; he previously worked for Beoing-Vertol who (as Piasecki) started putting tip weights in blades in the 1940s.

Here are some recommendations the FAA made in 1995 for the R-22... The complete text of this document can be found at:

<a href="http://www.opspecs.com/AFSData/FSBRs/Final/R22FSBR1.TXT" target="_blank">http://www.opspecs.com/AFSData/FSBRs/Final/R22FSBR1.TXT</a>

13. MISCELLANEOUS

13.1 The following recommendations of the FSB pertain to the
certification of the aircraft and suggested design changes to certain
systems as improvements deemed necessary for ensuring safe operations
of the R-22.

13.1.1 Carburetor air temperature system should
incorporate a relocated probe for accuracy of readings of real time
carburetor air temperatures. Application of carburetor heat should
be initiated at all low power settings (approaches and autorotations)
regardless of atmospheric conditions to preclude engine stoppage due
to carburetor ice and reinforce pilot training.

13.1.2 Improved rotor speed governor system for the R-22
to reduce the possibility of rotor speed decay due to pilot
inattention.

13.1.3 Longitudinal and lateral dampers in parallel with
the R-22 cyclic controls to impede abrupt movement of the cyclic.

13.1.4 Low rotor RPM warning system horn should be made
more audible. Wiring through the headphone (ICS) system or audio
panel may increase pilot awareness.

13.1.5 Redesign of cyclic system to include incorporation of
dual cyclic controls as opposed to single teetering control system so
as to increase pilot accessibility at each station.

13.1.6 Modification of Rotor/Engine RPM monitoring system
(tachometer) to increase visible marking range for usable rotor RPM
range (e.g.; 50% to 116%)

13.1.7 Increase inertia of main rotor system

13.1.8 Revise FAR Part 27 to consider main rotor system
inertia in single engine helicopters.

To: Tain't natural

I believe the primary reason for adding the tip weights was to establish the mass balance of the blade. On early Sikorsky blades they used lead shot which was fixed into the tubular spar of the blade. With the advent of the metal blades they used metal weights to establish the spanwise mass balance and the weights could be moved chordwise to neutralize the tendency for the blade to climb or dive. I think the same basic principle applied to all helicopters at that time. Of course the addition of the tip weights added a higher moment of inertia to keep the blades moving in the event of a power loss.

Portion of article on AVweb.
For complete article see: <a href="http://www.avweb.com/articles/rotorrpm.html" target="_blank">http://www.avweb.com/articles/rotorrpm.html</a>

&gt;"Helicopters with low-inertia rotor systems are extremely unforgiving of low-rotor rpm. Actually, all rotor systems are unforgiving of low rpm, but a low-inertia system loses rpm faster, which requires the pilot to react quicker to prevent low-rotor rpm from reaching the critical stage.

At this point, many helicopter pilots ask "why not just add some blade tip weights to, say, a Robinson R22 helicopter, to make it into a high-inertia system?"

"It's not as easy as that," says Frank Robinson, the R22's designer. "Rotor blade tip speeds are similar for all helicopters regardless of the size of the machine, because they are all limited by the speed of sound in air. The stored energy of a tip weight is only dependent on tip speed, therefore, a one-pound tip weight added to the 50-foot diameter rotor of a large helicopter would store the same energy as a one-pound tip weight added to the 25-foot diameter R22 rotor. However, the centrifugal force produced by a tip weight is inversely proportional to the rotor diameter, so the one-pound tip weight would produce twice as much centrifugal force in the R22 rotor as it would in the larger helicopter rotor, even though it would not store any more energy. The increased centrifugal loads carried by the blades, the pitch change bearings, and by the rotor hub would all be twice as great. Clearly it is very difficult to engineer a small helicopter with a high-inertia rotor." "&lt;

_________________

Frank Robinson's statements about the same amount of energy in both rotors and about the centrifugal ratio of 2:1 between the rotors are correct.

I believe that his position breaks down when he does not consider that the large rotor has four times the area of the small rotor. If both rotors have the same disk loading then the small helicopter is one quarter the weight of the large helicopter. In other word; the small helicopter actually has an increase of 4-times the relative energy of the large helicopter.

It appears, if my calculations are correct, that for the same increase in centrifugal effect the smaller helicopter actually has twice the increase in relative energy.

He also mentions that "Clearly it is very difficult to engineer a small helicopter with a high-inertia rotor" and yet it is claimed that the very small (ultralight) UltraSport helicopter has enough inertia to land, takeoff and re-land in autorotation.

_____________

There is no intent to find fault with the R-22 helicopter, merely clarify facts and features.

heedm, or others may wish to recheck the physics.

[ 28 December 2001: Message edited by: Dave Jackson ]</p>

It would seem to me that on larger helicopters, where the “tip weights” are added to establish the mass balance of the rotor blade, the engineers have taken into consideration the fact that the weights will have to be added and the manufacturing tolerances of the blades being quite close the tip weights will fall into a fixed range. Knowing this they can calculate the loads of the blade on the rotorhead and allow a sufficient safety factor. It should also be noted that the high inertia rotor systems are not made that way by the addition of tip weights but by the weight of the blades themselves. If this were the case then Frank Robinson could have calculated the amount of weight addition necessary to provide a higher moment of inertia to his blades. Another point is that in AD 95-26-04, which dictated, the addition of cautions in the R-22 and R-44 POHs also stated that it was recommended that Robinson do something to increase the moment of inertia. If he had not calculated the centrifugal loads in the initial design then it would seem that in order to do so at this time he would have to completely redesign the rotorhead and the blades to take the additional loads.

This in MHO makes his statement about the difficulty of designing a high inertia rotor system in a small helicopter a bit self serving.

[ 28 December 2001: Message edited by: Lu Zuckerman ]</p>

I do believe that in the early Sikorsky craft like the R4 only static balancing was done - if they weighed the same they were deemed to be a match. As a result some of those machines would shake the fillings out of your teeth. (I'm open to correction here, it's just what I've heard.) Frank Piasecki would weigh his blades, then hang three of them up and swing them. On the one that swung slowest, he would move a balance weight closer to the hub. The one that swung fastest, he'd move the weight towards the tip. Voila - three dynamically balanced blades.

To: T'aint natural

When I was first exposed to Sikorsky helicopters we worked on HOS-1s and R-4s but at the level of instruction we never got into the mass balancing of the fabric blades and wooden tail rotors. The S-51s that I maintained had just been converted to having hydraulic boost and the fabric blades had been replaced by metal blades. Our helicopters still had a three blade tail rotor made from wood. These too would eventually be replaced by a two blade tail rotor made of metal.

When I went to work for Sikorsky I was involved in a long term training program that included class room instruction and working in the shop to include building blades, mass balancing blades and whirl testing of blades to establish aerodynamic properties and to establish neutral climb and or dive tendencies.

The blades were balanced on a knife edge balance beam that had a fixed weight on one end. The weight was held in a neutral position with a mechanical lock. When the blade was attached the lock was released and the weight would move down and the blade would move up. A machined metal weight was attached in a neutral spot on the blade tip. The tip cap and the attaching screws were weighed and then set aside. Smaller weights and attaching hardware were placed on the blade outboard end until the blade was in perfect balance. Then the weight of the tip cap and screws were removed and the tip cap attached which kept the blade in balance. The tolerance was ¼ inch ounce.

The blade CG was calculated and this information was stenciled on the underside of the blade.

The blade was then sent to the whirl stand. Two brand new blades would then be installed on the whirl stand rotor head and a third master blade would also be installed. The master blade had built into it all of the desirable aerodynamic and aeromechanical characteristics. The pitch link for each blade had a proof ring (strain gage) to measure the feedback forces from each of the three blades. First the blades were spun up and measurements taken along with a blade track using a canvas strip. The trailing edges of the two blades under test were bent up or down to bring the blades into track. On the second spin up they would check the feedback forces on the two test blades cross checking them against the master blade. Other adjustments were made until the forces on all three blades were the same. Then the blades were checked for a tendency to climb or dive when cyclic and collective pitch were input into the system. If the blade wanted to climb the tip cap on that blade was removed and the balance weights were moved forward. If the blade wanted to dive the opposite movement of the weight would be made. Then the tip cap was replaced and the whirl test would then verify that the two test blades had the same characteristics of the master blade.

Hopefully I didn’t leave anything out or get the sequence mixed up. This all happened in 1955-56.

There has been some concern about the amount of rotor inertia in the R-22.

I just calculated the time to fully dissipate the energy in the rotors of both the Robinson R-22 and the Schweizer/Hughes 300C. The data used for the helicopters' moments of inertia, tip speeds and horsepowers etc. came from Prouty's 'Helicopter Performance, Stability and Control'.

It is interesting to note that both helicopters appear to have almost identical rotor decay rates; at least from a theoretical perspective

Has anyone done autorotations in both helicopters and can comment from a practical perspective?

R22 shut down procedure
 

Hi all,. .been chatting to a mustering pilot (r22) in Oz here and here told me standard practise for shutdowns was to turn off the mags. He had actually been told company policy was not to pull the mixture/cutout as cable breaks in the outback were too problematic(?).

Having thought this through a wee tad..................well a little fuel in the pots of a warm/hot engine will vaporise quick smart so shouldn't be a problem.

Initial reaction was "you what" (yrs of being told/shuting down meself the standard way) but really nothing wrong here...........or is there

Opinions Please (horror stories due to ......gratefully accepted)

Cheers & fly safe. .Hone

Im not totally sure but I have often wondered the same thing, I mean isnt that how one shuts off his car? Although being young I have never dealt with a car with mixture control.

. .Although I would still stick to the factory recomended procedure. <img src="wink.gif" border="0">

[ 23 January 2002: Message edited by: baranfin ]</p>

This is based on what I learned over fifty years ago (52 to be exact). If you shut the engine down by turning the mags off and the twist grip is in the secured position the vacuum behind the butterfly will cause a very significant increase in the suction (I was told that there is no such word it is a differential of pressure). This will draw in a large amount of fuel from the idle jets and possibly the main jets depending on which side of the butterfly they are located. This raw fuel will be ingested into the hot cylinder and it may as stated above vaporize but it is still highly combustible. If there is a hot spot in the cylinder the fuel will ignite and the resultant firing of an individual cylinder could develop sufficient force to crack the crankshaft.

later model cars are turned off by the computer(fuel and spark together) a lot of later carbyed cars used to have devices that turned the fuel off when the ignition was switched off(fuel cut off soliniods) to provent run on from a hot engine. older cars had less compression and diddnt suffer from running on so much.. .i dont know about cracking the crank lu and i dont see how there could be more vacuum when the engine slows down but the best way to shut an engine down in a plane would be to take away the fuel so a flick from the magneto wont start the prop when your having a bit of a look at it.. .helicopters its harder to accidently turn the engine and cause any unwanted spark so it probably doesnt matter so much.

if you dont use the mixture cutoff, how do you know its servicable? <img src="confused.gif" border="0">

R22 maggie check 75%
 

i think the magie check should be done at 104% insted of 75%. its much easier to tell a crook plug. i wonder why they changed it?? <img src="mad.gif" border="0">

noise abatement ?

Have heard the cooling fan is subject to cracking due rough running at that speed.

Here in the UK we have some very cold and damp days, especially at this time of year, I feel that if you didn't run the fuel out of the system before earthing your mags it could store a problem for the next time the craft was started up, with the possibility existing that the previouse or next pilot could/be a student who left the throttle open enough to cause some initial start up possibility of an overspeed, also excess fuel could drain into the oil and create an explosive possibility in the crankcase!. .but why not follow the manufacture's route, and when was the last time anyone was stuck for a wire breakage on the fuel cut off?. . <img src="eek.gif" border="0">

Sorry, I seem to have posted this answer on the wrong thread, should be on Mags shutdown R22, many apologys

[ 24 January 2002: Message edited by: Vfrpilotpb ]</p>

To: vorticey

On opposed engines used on a helicopter you do not have the flywheel effect of a propeller but you do have a flywheel which has a relatively high moment of inertia. When you shut down by turning off the mags the engine will continue for several revolutions creating a high vacuum behind the closed butterfly drawing in fuel from the jets. As I had indicated if this fuel is drawn into a cylinder that has a hot spot (carbon build up on the valves or on the cylinder or plug the fuel can ignite. Under normal start-up of the engine the starter is providing the motive power and all cylinders should start firing in sequence after the initial firing of a single cylinder. However, at shut down there might be only one cylinder that fires and it must rotate the crank along with the resistance of the other cylinders and the weight of the rotating mass. This can put a localized torsional stress on the crank and if sufficiently strong can cause the crank to crack. The US Army had a lot of problems on their engines used on the H-13s and the H-23s suffering cracked cranks. Although not from improper shut down but it illustrates that certain conditions can cause the crankshaft to break.

Another problem is fuel entering a cylinder and being ignited by a hot spot while the intake valve is open resulting in a backfire against a closed butterfly valve on the carb.

[ 23 January 2002: Message edited by: Lu Zuckerman ]

[ 23 January 2002: Message edited by: Lu Zuckerman ]</p>

Same here. We were told that the check was to be done at 75% to prevent cooling fan cracks and excessive stresses.

Also something to do with vibration alterations when you do get a duff-un.

"Some days you are the pigeon, some days you are the statue!"

MY THEORY IS THAT CUTTING THE IGNITION SOURCE ALLOWS UNBURNT FUEL MIXTURE TO WASH LUBRICANT FROM CYLINDER BORES CAUSING DAMAGING FRICTION UPON STARTUP,IF THIS OCCURS REGULARY THE RESULT. .WOULD BE PREMATURE WEAR AND LOSS OF VALUBLE COMPRESSION.KEPT IT AS SHORT AS I COULD (COULD HAVE GONE ON & ON ETC).