first taxi trials / sticky brake cylinders

[Rene Bubberman]

Hi Group,

Yesterday PH-VII moved for the first time on its own power! See:
http://www.youtube.com/watch?v=_xwkdtioZ0I#GU5U2spHI_4

Still to solve: BMA?s altitude calibration, fuel sensors (not working at all) and sticky brake cylinders. Did you have problems with them? Ours will not return to the zero position, but I understand this is quite common and that there are some ?proven? fixes for it, like exchanging the two bolt-hinges for one axis and applying booster springs around the cylinder pistons. I'll try these wednesday, but if anybody has another advise, please let me know!

kind regards,

Ren? Bubberman
PH-VII | RV-7 | TipUp | TMX 360 Fadec
Almost there!

http://websites.expercraft.com/PHVII/

[Davepar]

Congrats Ren?!

I still have slightly sticky brake pedals. I have the single axis pivot bolt, and they still don't return completely. They spring back except for the last 1/8". The plane taxis fine, but I have trouble pushing it back into the hangar. I'm planning on loosening up the bolts a bit more and then trying an additional spring.

[rvbuilder2002]

Your peddals should be installed so that the pivot points at the bottom have no resistance. This solves most of the sticking brake problems

[664781]

Put the additional springs on ASAP. I went thru a set of brakes in 50 hours and a friend went off the runway because if this. That last 1/8 of an inch makes a lot of difference!

[Mike S]

Originally Posted by Rene Bubberman

and applying booster springs around the cylinder pistons.

The Matco cylinders already have a spring internal that is under the piston. It pushes the piston back out of the bore.

If you are going to add a spring, put it on the shaft extending from the cylinder, to help pull the piston back up.

The external spring is what is used on Cleveland cylinders, which just happen to fit in place of the Matco units.

And, the Clevelands work.

[N916K]

Originally Posted by Mike S

The Matco cylinders already have a spring internal that is under the piston. It pushes the piston back out of the bore.

I ran into this problem when I first flew my 9A. I went to Matco's website and saw that there was a spacer and a spring under the piston. I called Matco about it and they make a larger spacer to increase the preload on the piston. I ended up increasing the clearance on the pivot bolt instead and once the pistons broke in I have had no problems. If I was to do it again I would pull the master cylinder apart and put a strong spring in or a longer spacer.

Cam

[rvbuilder2002]

Originally Posted by Mike S

And, the Clevelands work.

I can't help laughing to my self at this statement...
If you have been arounbd RV's for a few years you would know that the cleveland cyls went through a period of time were everyone accused them of having weak springs, etc.

It doesn't matter what cyls you use...if you don't properly set up the installation of the peddles, you will have brake problems.

I have been involved in the completion of about 10 RV's and the brakes all worked just fine without the installation of extra springs (on cleveland and matco cyls.)

[lucky333]

It takes about $10.00 to completely remove any doubt about Matco sticking, preloads, friction in the mechanism etc. etc. Add the springs. Matco's work just fine but (at least the ones I know, a couple of years ago) were VERY sensitive to shaft loads and friction in the system; anything that would keep the shaft from extending completely.

Springs are a cheap, light, simple way of ensuring that shaft extension will happen every time.

Brake thread

-A drivers might note the links in the thread that suggest that the standard Clevelands may be undersized for the application. This can lead to expensive problems. The new wing in question cost over $4000.00

Myself, I bought the fancy Grove master cylinders. Still going to put springs on em.

John