The Biplane Forum > Biplane Builder's Forums > Steen Skybolt > Skybolt Miscellaneous > Inadequate Skybolt Brakes



Help Support Biplane Forum by donating using the link above or becoming a Supporting Member.
Reply
 
Thread Tools Display Modes
Old 11-18-2017, 05:05 PM   #1
4deuces
Registered Users
 
Join Date: Apr 2008
Location: Mesquite, NV
Posts: 23
Liked 3 Times on 2 Posts

Default Inadequate Skybolt Brakes

I continue to have poor braking power. I have difficulty holding the Skybolt during run-up while almost standing on thee brakes. I have a Cleveland reservoir type master cylinder (5/8" bore) which I believe are properly rigged. I have bled them several times (normal and reverse), new pads, changed rotor disc and did many breaking-in runs to no avail. The conclusion I have come to is that the original brake pedal design is the problem.
I searched the forum and cannot find any discussion of inadequate Skybolt brake design. There is no mechanical advantage from the design. In fact, there is there is a mechanical disadvantage. The brake pedal height(from its rotation axis) is about 3 inches but the arm from the brake pedal to the brake cylinder is 4 inches giving a mechanical advantage of 0.75. So no matter how much you push on the brake pedal you cannot achieve enough hydraulic pressure on the brake pads. I am about to shorten the brake arm about a 1.5 inches to give me a 2:1 mechanical advantage.
Am I barking up the wrong tree and is there any other options. I am also considering a kit that will result in a smaller bore and give an additional hydraulic advantage.


4deuces is offline  
 
Reply With Quote
Old 11-18-2017, 05:11 PM   #2
Timbob
BiP_SUPPORTER.png
 
Join Date: Oct 2008
Location: Socorro, NM USA
Posts: 476
Liked 84 Times on 61 Posts
Likes Given: 4

Send a message via MSN to Timbob
Default

Pictures of the system would help folks troubleshoot for you.


__________________
Tim
Timbob is online now  
 
Reply With Quote
Old 11-18-2017, 05:20 PM   #3
raymoeller
Registered Users
 
raymoeller's Avatar
 
Join Date: Nov 2011
Location: Willowbrook, Illinois
Posts: 841
Liked 240 Times on 160 Posts
Likes Given: 199

Send a message via MSN to raymoeller
Default

I don't think you're the only one... I noticed in mine (540 equipped) that I can only get it up to around 1800 or so and it wants to slip... now that could be because the brakes aren't really broken in yet... but I think my neighbor has the same problem with his Pitts S1. I "kinda" understand the concept you're talking about regarding the mechanical leverage, but if you find a modification from the plans that works well, please share it. I'm running Clevelands as well.
__________________
Everything in this life has its time. Flying isnt about driving the machine through the air.. its about the melding of man with the machine.. becoming as one.

Steen Skybolt- Under Construction, Pitts S-1C- Under Restoration/Modification
raymoeller is offline  
 
Reply With Quote
Old 11-18-2017, 05:30 PM   #4
Neil
BiP_LIFETIMESUPPORTER.png
 
Neil's Avatar
 
Join Date: Nov 2006
Location: Monroe, LA Work at F89 Winnsboro, LA
Posts: 5,865
Liked 781 Times on 589 Posts
Likes Given: 269

Default

Could be a ratio problem but if the brake pads are not broken in properly they won't hold well.
__________________
OOPS you can fix with a paper towel. UH OH is going to require more money.
Building Acro Sport II NX11ND
Plans #425
Neil is offline  
 
Reply With Quote
Old 11-18-2017, 05:38 PM   #5
will moffitt
Registered Users
BiP_SUPPORTER.png
 
will moffitt's Avatar
 
Join Date: Jul 2012
Location: Anacortes, Wa
Posts: 1,307
Liked 314 Times on 224 Posts
Likes Given: 511

Default

Count your blessings. My brakes are off a 182 and they are too good, on a 800# plane. They were leaking so I cleaned them up, new o-rings and a slight touch at walking speed and the tail was up. I detuned them and with reasonable pressure they almost hold on runup. I have no problem with turns. I also changed the geometry, not ratio but position as I had difficulty keeping my toes off the brakes. Now I have to reach for them. Works for me.

will
will moffitt is offline  
 
Reply With Quote
Old 11-18-2017, 09:01 PM   #6
Dave Baxter
BiP_LIFETIMESUPPORTER.png
 
Join Date: Nov 2007
Location: St. Helens, Oregon
Posts: 1,247
Liked 496 Times on 290 Posts
Likes Given: 1

Default

One other thing you might consider is new brake discs in that you would think worn and grooved discs would make little difference, but they do, honest!

The brake arm and master cylinder relationship can make for wimpy or aggressive brakes. I think those on the Skybolt, and many other tail wheel home built's were purposely designed to be less aggressive, as it takes very little to put one on its back under the right circumstances.

Also many brake and master cylinder combinations, plumbing and as you have discovered the leverage arm and distance can all add or subtract from ideal braking.

The SA-100 single place Starduster for example designed in the late 50s and of the 100 or so built during the 60s most had shoe brakes and some were even mechanical, skip forward to the 70s when Cleveland's became more available mostly 600X6 off of certified airplanes and many switched to brakes meant for nose gear airplanes with gross weights of over 2000lbs! The results were over half of those that were converted, many with numerous accident free previous hrs of flight time, were quickly on their backs!

So as Will so eloquently pointed out one might not what to increase the leverage or braking power by a large margin. The Skybolt I had with a 540 had plans built brake linkage, about all I did was tilt the pedals back so as to keep off of the brakes unless I needed, and it seemed to hold on run ups with no problem. So be cautious, just my take... Dave
__________________
Dave Baxter
O-540 powered Skybolt Flying sold with 63 hrs on the clock.
Finished Two Stardusters, 180 and 540 Also built a Marquart MA-4 and have an SA-100 Starduster project

Last edited by Dave Baxter; 11-19-2017 at 06:08 AM.
Dave Baxter is offline  
 
Reply With Quote
Old 11-19-2017, 12:31 AM   #7
Lotahp1
BiP_SUPPORTER.png
 
Lotahp1's Avatar
 
Join Date: May 2012
Posts: 3,621
Liked 688 Times on 496 Posts

Default Inadequate Skybolt Brakes

I guess Iím of the ďI like soft brakesĒ crowd also. I know my Starduster Too has Matco triple puck disc brakes with Cleveland 10-19 master Cylinders and it was just barley able to hold at 1700rpm With the Ranger. Probably like others have said it was a new pad issue more than anything. Itís kinda hard to go break the pads in by stomping on brakes like you do in a nose wheel plane. I used to break in pads by practicing short field landings by really getting on the brakes hard and as soon as on ground Iíd raise the flaps to get the weight to shift to the tires from the wing. Kinda hard to do in a tailwheel. Or at least mentally it is for me. Whatís the best way to break in new pads on a tailwheel you donít want on itís back by getting to aggressive?
Lotahp1 is offline  
 
Reply With Quote
Old 11-19-2017, 01:01 AM   #8
TFF1
Registered Users
 
Join Date: Apr 2010
Location: Memphis,TN
Posts: 2,764
Liked 479 Times on 375 Posts
Likes Given: 1

Default

Yes to working on the correct peddle ratio. My SD1 came to me after a flip. Old owner said he could stand it on the nose any time he wanted if he was moving at any good clip. He just landed and coasted down before he used brakes, until he got himself in need of brakes one day. Went over like a Keystone Cop movie. The old setup was 1" peddle to 2 " master cylinder; no way not to lock the brakes. Sounds like you have the opposite problem.
TFF1 is offline  
 
Reply With Quote
Old 11-19-2017, 02:34 AM   #9
Larry Lyons
Registered Users
BiP_LIFETIMESUPPORTER.png
 
Larry Lyons's Avatar
 
Join Date: Oct 2012
Location: Stockton, IL.
Posts: 3,441
Liked 798 Times on 613 Posts
Likes Given: 1447

Default

Also make sure cylinders are properly matched. Different diameters improperly matched can get you into trouble in a heart beat.
__________________
Larry Lyons
Rebuilt:
Smith Mini, flying
Taylorcraft, almost flying
and on going Taylorcraft project

In dog beers I've only had one!
Larry Lyons is online now  
 
Reply With Quote
Old 11-19-2017, 11:51 AM   #10
PittsDriver68
Registered Users
 
Join Date: Jan 2013
Location: NH
Posts: 3,696
Liked 968 Times on 697 Posts
Likes Given: 2

Default

I will guess that most folks don't break in their pads. They just put them on and expect them to work. And they mostly do.

The first time that I read the break in instructions for the Cleveland/Rapco brake pads I was surprised at the instruction to really get the pads "cooking". I see very few owners and mechanics actually performing the procedure described in

http://www.aeroinstock.com/wp-conten...tion_Final.pdf

Best of luck,

Wes
PittsDriver68 is offline  
taff Likes This 
Reply With Quote
Old 11-19-2017, 04:14 PM   #11
4deuces
Registered Users
 
Join Date: Apr 2008
Location: Mesquite, NV
Posts: 23
Liked 3 Times on 2 Posts

Default

Thanks for all the great replys. As I suspected the original Skybolt design was avoid aggressive braking and a forward somersault. For now my easiest fix is to get new master brakes(Matco) with a reduced piston bore. Calculations show a 60% increase in hydraulic force. As far as breaking in the brakes, I've tried several times per instructions. However, it's hard to break them in if you can't get enough pad pressure.

Dan Hoffman
4deuces is offline  
 
Reply With Quote
Old 11-20-2017, 07:36 PM   #12
mreinh3233
Registered Users
 
mreinh3233's Avatar
 
Join Date: Jun 2014
Posts: 224
Liked 56 Times on 36 Posts
Likes Given: 219

Default

Quote:
Originally Posted by 4deuces View Post
Thanks for all the great replys. As I suspected the original Skybolt design was avoid aggressive braking and a forward somersault. For now my easiest fix is to get new master brakes(Matco) with a reduced piston bore. Calculations show a 60% increase in hydraulic force. As far as breaking in the brakes, I've tried several times per instructions. However, it's hard to break them in if you can't get enough pad pressure.

Dan Hoffman
I believe total piston volume must be less in the wheel pistons than total piston volume in the master cylinder to attain hydraulic advantage, or am I confused? Think of your car, the wheel cylinders are smaller than your master cylinder but there are four of them.
mreinh3233 is offline  
 
Reply With Quote
Old 11-20-2017, 08:45 PM   #13
4deuces
Registered Users
 
Join Date: Apr 2008
Location: Mesquite, NV
Posts: 23
Liked 3 Times on 2 Posts

Default

For non-compressible fluids what counts is the pressure generated on the brake caliper. Pressure is force/area so the smaller the area the greater the pressure for any given force applied.

Dan
4deuces is offline  
 
Reply With Quote
Old 11-20-2017, 09:10 PM   #14
IanJ
BiP_LIFETIMESUPPORTER.png
 
IanJ's Avatar
 
Join Date: Jun 2007
Location: Seattle, WA, USA
Posts: 1,411
Liked 227 Times on 173 Posts
Likes Given: 77

Send a message via MSN to IanJ
Default

Would it make sense/be possible to make a new arm with multiple attach points for the master cylinder? It'd be cool to be able to test different ratios without having to weld a new arm on each time.
__________________
Marquart Charger MA-5 build: makin' ribs
1956 Champion 7EC, "Norbert"
IanJ is offline  
 
Reply With Quote
Old 11-20-2017, 09:42 PM   #15
FireboltEric
Registered Users
BiP_SUPPORTER.png
 
FireboltEric's Avatar
 
Join Date: Nov 2015
Location: Wichita, KS
Posts: 50
Liked 17 Times on 11 Posts
Likes Given: 9

Default

I have the same issue with my Bolt as well. I would like a bit more force. But just shortening the arm will change the pedal angle at full rudder travels. You would have to move the lower cylinder mount point as well. I am going to try just lengthening the top of the pedals an inch or so and see if that improves force.
FireboltEric is offline  
 
Reply With Quote
Old 11-23-2017, 03:31 PM   #16
Larry Lyons
Registered Users
BiP_LIFETIMESUPPORTER.png
 
Larry Lyons's Avatar
 
Join Date: Oct 2012
Location: Stockton, IL.
Posts: 3,441
Liked 798 Times on 613 Posts
Likes Given: 1447

Default

Just a data point but to create pressure you need your slave cylinder to be larger than your power cylinder. Another words the cylinder on the pedal is say 1/4" dia and at the brake pad the cylinder is 1/2" dia. You doubled the dia. but you increased the area 4 times. So a 25 pound push on the pedal will give you a 100 pound push at the slave or wheel cylinder. Same principle as your hydraulic jack, small cylinder attached to the handle, large cylinder doing the lifting. By changing the ratio you can control how much brake power you have available.
__________________
Larry Lyons
Rebuilt:
Smith Mini, flying
Taylorcraft, almost flying
and on going Taylorcraft project

In dog beers I've only had one!
Larry Lyons is online now  
taff Likes This 
Reply With Quote
Old 11-24-2017, 03:09 PM   #17
4deuces
Registered Users
 
Join Date: Apr 2008
Location: Mesquite, NV
Posts: 23
Liked 3 Times on 2 Posts

Default

I agree and this is the reason I am currently installing master cylinders with a piston diameter of only 0.60" (vs the usual 0.625"). Although this seems like a small change it should provide 60% more force to the slave piston.


4deuces is offline  
Larry Lyons Likes This 
Reply With Quote
Reply


Tags
brakes, inadequate, poor, skybolt

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Skybolt Brakes Texmex Steen Skybolt 9 02-23-2016 12:44 PM
Help with brakes ssmdive Pitts Miscellaneous 14 03-13-2015 01:09 PM
Brakes, brakes, and more brakes! (and paint) :) George_Pfaltzgraff Steen Skybolt 5 04-21-2014 06:15 PM
Skybolt wheels & brakes mekstrand Steen Skybolt 6 04-22-2012 11:17 PM
wheels & brakes - skybolt pelican Skybolt Miscellaneous 9 12-11-2009 03:04 AM