REFLECTOR: Main Gear Hydraulic Cylinder/ Speed Brake

[robajohnson at comcast.net]

>>Well I’m at the point where I need to put the MG hard points in<<

Why are you feeling compelled to put in the hard points now? I would wait until you get the main gear in. Then you can line everything up nice and neat before you cut any holes. 

Depending on your answer I am not sure if this is a relevant story or not but I'm in a story telling mood for some reason so... :-)

Early in the build process I had a partner named Bill. He had what I call a "blueprint" mentality. For example, he would take the page out of the manual and lay out every hard point on the cabin floor and *start cutting*. Months even years ahead of when we needed them. Putting in the back seats one of the very last things I did to the plane but he had the hard points glassed in on day 4.  :-)

I used to tell him to put something in place and see how it fit THEN cut drill etc. Plans are just that PLANS. They are not reality. He was flabbergasted. To him plans were like the commandments sent down to man by GOD himself. They MUST be right! 

I told him that even on the B1-B bomber program parts came with #40 pilot holes in them and we were always plugging up pilot holes and moving the rivet (hi-lock, taper-loc, huck whatever) holes to where they would FIT and still give you proper edge clearance, room to buck etc. etc. Drifting tolerances is a real engineering concept and most people in the industry just don't sweat it. Plans are theory. Holes are physical and they have to actually fit. Plans don't have to fit or even work for that matter. 
  
He just looked at me with that same look I get from people when I tell them I avoid hitting other airplanes the same way they avoid hitting other cars, by looking out the windshield! 

So he ended up doing the nose hear hydraulic cylinder hard point three times.The first time laid out with deadly accuracy to the plans. The cylinder would bottom out before getting full travel on the gear leg. So he ended up doing twice more . Each time it was still not quite right. I was getting very annoyed at the swiss cheese that section of the belly was starting to look like! For the fourth try we hooked everything up and swung the nose gear by hand a few times with me simply holding the L-angle cylinder. After a little trial and error we got it placed where the gear would go full travel both ways without the cylinder reaching the end of it throw on either end. *THEN* and ONLY THEN did I pop holes in the floor and cleco'd the L angle in. Swung the gear a few more times to make sure THEN we glassed in a hard point. 

That's EXACTLY how we did it at General Dynamics, Boeing, LTV (Old Vought) and Braniff.

Fit first, make holes later.

Rob

-------------- Original message -------------- 

> I’m putting a speed brake in my XL-RG during the build process, and I 
> had previously gotten info that if I mount the main gear hydraulic 
> cylinder just behind the speed brake, there is still enough room 
> behind the cylinder to get the system to work. Well I’m at the point 
> where I need to put the MG hard points in, and I’d just like to make 
> sure that I’m going not going to do something I’ll regret. I can’t 
> really know how much throw I need in the cylinder unless I go ahead 
> and completely mount the gear legs and mount all the hardware. 
> 
> It looks like mounting the forward end of the cylinder immediately 
> behind the speed brake will not allow the cylinder to extend fully. 
> But does it need to? How much throw is needed to pull the gear all 
> the way up? And if anyone has any photos or sketches or measurements, 
> that would really be helpful. I know that putting the speed brake on 
> an RG has been done, I'd just feel better if someone could reassure 
> me that mounting the cylinder immediately behind the speed brake will 
> work out ok. Tanks for your help. 
> 
> Randy and Becky Wharton 
> N248RB XL-RG 
> http://clik.to/velocity 
> 
> 
> 
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