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undercarriage retraction problem

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rowlandcarson(at)gmail.co
Guest

Posted: Sat Jun 06, 2015 1:48 am Post subject: undercarriage retraction problem

I’ve finally managed to satisfy myself that the flaps are operating over the correct range, and moved on to installing the undercarriage. After fitting the LG02 swinging arm to the LG01 mounting frame, I was still (just) able to operate the retract lever without any bungee assistance. Then I fitted the wheel and brake to LG02 and of course that made it too heavy to retract without the bungee.



Yesterday I fitted the bungee and was pleased to find a number of loops and tension that nicely balanced the weight of the undercarriage and allowed the lever to operate quite easily. However, I couldn’t quite get the lever into the “up” gate. Examination of everything showed that (1) the tyre was hitting the brake master cylinder and its elbow connexion and (2) the brake slave cylinder was catching the rudder cable.



Initially it looked as if LG02 might be too far to starboard, but I had taken care when fixing LG01 into the fuselage to have LG02 temporarily fitted, and inserted packing to keep LG02 equidistant from the tunnel at each side.



The other possibility that occurred to me was that (despite careful measurements against the manual callout) I’d pre-compressed the LG06 suspension block at bit too much, causing the distance between the LG08 pivots and the LG02 pivots to be too small, thus making the LG02 swinging arm retract too far.



I tried backing off the M8 stiffnuts a little (which involved removing and re-installing the bungee again - nobody mentioned how hard it is to thread the bungee around LG02B anchor tube) and that did seem to allow a little but more movement in the “up” direction but nowhere near enough to get the lever into the “up” gate. While looking at everything after that adjustment, it seems that the linkage is not quite going over-centre in the “down” position - it appears the 3 pivots are just about in line with each other. I wonder if lengthening the suspension assembly has caused that.



Can anyone suggest what I might be doing wrong, please, or any way to solve the problem?



in friendship



Rowland



| Rowland Carson          ... that's Rowland with a 'w' ...

| <rowlandcarson(at)gmail.com>            http://www.rowlandcarson.org.uk

| Skype, Twitter: rowland_carson      Facebook: Rowland Carson

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JonathanMilbank

Joined: 14 Apr 2012
Posts: 391
Location: Aberdeen area

Posted: Sat Jun 06, 2015 3:01 am Post subject: Re: undercarriage retraction problem

Hi Rowland. First let me state that I did all this construction stuff 20 years ago and that my aircraft was converted to tri-gear in November 2012, so it was operated as a mono for over 850 hours. Anyway, if memory serves me correctly the LG06 suspension block was hardly compressed at all before installation and only when the full weight of the aircraft was resting on the wheel, did the block become compressed. Thus if you were to have reached up into the wheel bay while lying under my aircraft, you would have found that the two bolts passing vertically through the block were loose i.e. had a few millimetres sliding end play.



Obviously this would suggest that the suspension block was not in compression while the wheel was retracted. It worked happily like this for about 17 years.



As regards bungee tension, I had it arranged so that when the aircraft was off the ground with wings and flaps fitted, the lever would rest comfortably around mid-travel in the gate. Thus during flight only a mild push was needed in either direction to either extend or retract the undercarriage. This was useful when practicing forced landings, allowing the lever to be used almost like a throttle as gliders do with speed brakes to help get into a field with more precision.

rowlandcarson(at)gmail.co
Guest

Posted: Sat Jun 06, 2015 4:09 am Post subject: undercarriage retraction problem

On 6 Jun 2015, at 12:01, jonathanmilbank <jdmilbank(at)yahoo.co.uk> wrote:



 	  Quote: 	
		   if memory serves me correctly the LG06 suspension block was hardly compressed at all before installation and only when the full weight of the aircraft was resting on the wheel, did the block become compressed. Thus if you were to reach up into the wheel bay while lying under your aircraft, you would find that the two bolts passing vertically through the block would be loose i.e. have a few millimetres sliding end play.


	


Jonathan - thanks for your message. I’d be happy to try the effect of further loosening the M8 bolts that hold the suspension assembly together, but after my first loosening there is now is barely enough thread protruding beyond the nuts to keep them in safety, so there’s not much room for further experiment.



I can believe that the weight of the aircraft will compress LG06 quite a bit and thus leave the bolts loose, but on initial assembly I found I had to use G-clamps to compress the thing enough to even get the nuts started on the threads.



in friendship



Rowland



| Rowland Carson          ... that's Rowland with a 'w' ...

| <rowlandcarson(at)gmail.com>            http://www.rowlandcarson.org.uk

| Skype, Twitter: rowland_carson      Facebook: Rowland Carson

| pictures: http://picasaweb.google.com/rowlandcarson

JonathanMilbank

Joined: 14 Apr 2012
Posts: 391
Location: Aberdeen area

Posted: Sat Jun 06, 2015 4:29 am Post subject: Re: undercarriage retraction problem

Your suspension block is probably different from mine, which was one of the earliest and came needing work done by the builder. It was red in colour, solid and thus needed holes bored through with a hole saw in a drill press. A band saw was needed to cut out 'V' wedges top and bottom and finally the factory decided that the block wasn't thick enough, so we had to add in a shim made from a piece of 1/4" ply board.

Therefore I guess that it's unsurprising that your problems are different. Still, you might have been in possession of one of the early blocks if you had bought an old kit from someone.

rowlandcarson(at)gmail.co
Guest

Posted: Sat Jun 06, 2015 4:39 am Post subject: undercarriage retraction problem

On 6 Jun 2015, at 13:29, jonathanmilbank <jdmilbank(at)yahoo.co.uk> wrote:



 	  Quote: 	
		   Your suspension block is probably different from mine, which was one of the earliest and came needing work done by the builder. It was red in colour, solid and thus needed holes bored through with a hole saw in a drill press. A band saw was needed to cut out 'V' wedges top and bottom and finally the factory decided that the block wasn't thick enough, so we had to add in a shim made from a piece of 1/4" ply board.

 Therefore I guess that it's unsurprising that your problems are different. Still, you might have been in possession of one of the early blocks if you had bought an old kit from someone.


	


Jonathan - no, my block is of the newer sort, black with the hole and the notches already cut out. Anyway, I suspect that the solution to my problem may lie elsewhere so I don’t want to focus on one thing to the detriment of the big picture!



in friendship



Rowland



| Rowland Carson          ... that's Rowland with a 'w' ...

| <rowlandcarson(at)gmail.com>            http://www.rowlandcarson.org.uk

| Skype, Twitter: rowland_carson      Facebook: Rowland Carson

| pictures: http://picasaweb.google.com/rowlandcarson

JonSmith

Joined: 21 May 2010
Posts: 110

Posted: Sat Jun 06, 2015 6:57 am Post subject: Re: undercarriage retraction problem

Hi Rowland,

I remember that the rubber block should be (pre) compressed such that the distance between the inside faces of the upper and lower reaction plates is 79mm. I believe that this measurement is critically important and that it would be a big mistake to differ from that.  (Older manuals referred to different points to measure from, bolt centres etc giving different distances but the end result was the same). 

I also remember reading that the most important part of the correct geometry regarding the over centre locking is the length of the retraction stops. They should have been manufactured in the factory such that they were correct but I've heard they were not always so, so perhaps they are worth checking?  When it's all set up correctly both retraction arms should touch their respective stops simultaneously and the retraction arms should be parallel with each other.  The geometry of the three bolt centres should also be correcting as per the manual, ie the centre of the middle pivot (top bolt of the rubber block assembly) should be 1/16 to 1/8" forward of the line between the other two centres.  This can all be checked and confirmed to be correct with the plane hoisted up and is easier with the wheel removed.

If the above is all correct then I guess you will have to look elsewhere for your problem and I don't really know what the answer might be?  Can the rudder cables/ fairleads be raised slightly?  Can the brake master cylinder be repositioned slightly?  

Good luck!  Below is a link to the FSB which gives details of the mandatory undercarriage checks just in case you haven't seen it - it is on the Europa Club site.



http://www.theeuropaclub.org/wp-content/uploads/2012/02/FSB004.pdf

_________________
G-TERN
Classic Mono

alan.twigg775(at)gmail.co
Guest

Posted: Sat Jun 06, 2015 8:51 am Post subject: undercarriage retraction problem

Rowland, you are welcome to pop over to Bicester, my undercarriage works well and the aircraft is up on a trestle.

Alan Twigg



Sent from my iPhone



 	  Quote: 	
		   On 6 Jun 2015, at 13:38, Rowland Carson <rowlandcarson(at)gmail.com> wrote:

 

 

 

> On 6 Jun 2015, at 13:29, jonathanmilbank <jdmilbank(at)yahoo.co.uk> wrote:

> 

> Your suspension block is probably different from mine, which was one of the earliest and came needing work done by the builder. It was red in colour, solid and thus needed holes bored through with a hole saw in a drill press. A band saw was needed to cut out 'V' wedges top and bottom and finally the factory decided that the block wasn't thick enough, so we had to add in a shim made from a piece of 1/4" ply board.

> Therefore I guess that it's unsurprising that your problems are different. Still, you might have been in possession of one of the early blocks if you had bought an old kit from someone.

 

 Jonathan - no, my block is of the newer sort, black with the hole and the notches already cut out. Anyway, I suspect that the solution to my problem may lie elsewhere so I donâ€™t want to focus on one thing to the detriment of the big picture!

 

 in friendship

 

 Rowland

 

 | Rowland Carson          ... that's Rowland with a 'w' ...

 | <rowlandcarson(at)gmail.com>            http://www.rowlandcarson.org.uk

 | Skype, Twitter: rowland_carson      Facebook: Rowland Carson

 | pictures: http://picasaweb.google.com/rowlandcarson

JonSmith

Joined: 21 May 2010
Posts: 110

Posted: Sat Jun 06, 2015 10:21 am Post subject: Re: undercarriage retraction problem

Rowland, just a further thought, you haven't set it up so that it's trying to retract the wheel too far/ too high?  Whereas the undercarriage downlock gate and set up IS critical I don't think the exact position of the undercarriage lever UP lock gate is quite so important.  Obviously you want it up as much as possible and not too low but it can't of course go up too far.  Adjusting the rear latching face of the upgate rearwards slightly would mean the wheel wouldn't lock up quite as far but it might then not foul the items you mentioned.  You would then have to completely re-set up the flap retraction adjustment again with probably a new flap retraction horn etc....!

Maybe looking at Ian's plane as he mentioned above would give you a very good comparison.

Cheers,

_________________
G-TERN
Classic Mono

keithhickling(at)clear.ne
Guest

Posted: Sat Jun 06, 2015 4:37 pm Post subject: undercarriage retraction problem

Rowland,

1) I can't remember why, but I also ended up with the wheel contacting the 

brake master cylinder and a rudder cable. I had to move one of the rudder 

cable guides slightly, and as jon suggested I had to file back the up gate 

slightly so the swing arm did not retract quite so far. As jon said, that 

meant having to readjust the flap mechanism.



2) The geometry is complex, but as jon said I think the amount of 

precompression of the rubber block is critical to getting the correct amount 

of overcentre with the gear down, so the measurement specified in the manual 

is important. Ron Parigoris has written a couple of nice emails on the list 

concerning the geometry and the fact that on some u/c frames one or both of 

the stops were not the correct length and needed filing back a little to 

achieve the overcentre position. I seem to recall that there have been a 

couple of expensive u/c collapses associated with inadequate overcentre or 

slight undercentre positioning. The down gate is not strong enough to hold 

the gear down if it is not overcentred against the stops.



Good luck !



Regards,

Keith.

--

JonSmith

Joined: 21 May 2010
Posts: 110

Posted: Sat Jun 06, 2015 9:14 pm Post subject: Re: undercarriage retraction problem

Keith - right on - it WAS Ron Parigoris who wrote about this at some length a few years ago - sorry Ron, I couldn't remember who it was.  If Ron reads this perhaps he might be kind enough to reproduce his e-mails again for the benefit of our fading memories! Cheers,

_________________
G-TERN
Classic Mono

rparigoris

Joined: 24 Nov 2009
Posts: 797

Posted: Sun Jun 07, 2015 4:29 am Post subject: Re: undercarriage retraction problem

Hi Group



Here's some info on over-center in gallery:

http://www.europaowners.org/main.php?g2_itemId=27433



Ron Parigoris

rowlandcarson(at)gmail.co
Guest

Posted: Sun Jun 07, 2015 9:42 am Post subject: undercarriage retraction problem

On 6 Jun 2015, at 19:21, JonSmith <jonsmitheuropa(at)tiscali.co.uk> wrote:



 	  Quote: 	
		   Rowland, just a further thought, you haven't set it up so that it's trying to retract the wheel too far/ too high?  Whereas the undercarriage downlock gate and set up IS critical I don't think the exact position of the undercarriage lever UP lock gate is quite so important.  Obviously you want it up as much as possible and not too low but it can't of course go up too far.  Adjusting the rear latching face of the upgate rearwards slightly would mean the wheel wouldn't lock up quite as far but it might then not foul the items you mentioned.  You would then have to completely re-set up the flap retraction adjustment again with probably a new flap retraction horn etc….!


	


Jon - thanks for your message (and thanks too to Alan, Keith, Ron and Alfred for their helpful contributions to this topic).



I was coming to the same conclusion as you, that the slot for the retract lever must be slightly too long. Not sure why this should be as my journal (and my memory!) doesn’t seem to indicate that I extended the slot from the as-supplied state. Anyway, I think that will be the answer to my problem - in effect, don’t try to retract the gear so much!



As you say, once I have restored the suspension block compression to the correct value and checked for correct over-centring of the mechanism in the “down” position, I’ll have to file the “up" gate so that the lever latches _before_ any contact between the U/C and other parts. Then go back to the flap control; first get a new FL19 from the factory then go through the whole adjustment process again to find the right position for the hole in FL19.



Once it’s all done, I wonder would there be any need to provide some sort of stop to prevent the retract lever moving too far forward? I think I’ll worry about that when I see how much aftwards extension of the “up” gate is needed.



Thanks again to the Europa community for all your help and encouragement.



in friendship



Rowland



| Rowland Carson          ... that's Rowland with a 'w' ...

| <rowlandcarson(at)gmail.com>            http://www.rowlandcarson.org.uk

| Skype, Twitter: rowland_carson      Facebook: Rowland Carson

| pictures: http://picasaweb.google.com/rowlandcarson

Remi Guerner

Joined: 14 Dec 2010
Posts: 284

Posted: Sun Jun 07, 2015 11:38 pm Post subject: Re: undercarriage retraction problem

Rowland,

What type of tyre did you installed? 7.00x8 or 8.00x8 ? The bigger tyre does not allow the gear to get to the fully retracted position as shown in the Manual. You can live with that and adjust the lever slot up limits accordingly. Then you have to accept that the retracted wheel protudes a little bit more in the slipstream. This is a small inconvenience compared to the better ground clearance provided by the bigger tyre. 

Regards

Remi

F-PGKL, XS monowheel, 1200 hours

rowlandcarson(at)gmail.co
Guest

Posted: Wed Jun 10, 2015 2:21 pm Post subject: undercarriage retraction problem

On 8 Jun 2015, at 08:38, Remi Guerner <air.guerner(at)orange.fr> wrote:



 	  Quote: 	
		   What type of tyre did you installed? 7.00x8 or 8.00x8


	


Remi - my tyre, as supplied originally with the kit, is marked 8.00-6. I am intending to adjust the “up” gate of the retract lever and then re-set the flap travel - I already have my new FL19 from Karen at the factory.



in friendship



Rowland



| Rowland Carson          ... that's Rowland with a 'w' ...

| <rowlandcarson(at)gmail.com>            http://www.rowlandcarson.org.uk

| Skype, Twitter: rowland_carson      Facebook: Rowland Carson

| pictures: http://picasaweb.google.com/rowlandcarson

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