Alternative spring gear

[Little Scrapper]

Curious if anyone has read this, seen it in person or wondered about its effectiveness?

New die spring landing gear on a Pietenpol, 10 a.m.-4 p.m.

Friends, Last week I wrote a report of the weight & balance and performance of Bob Lester’s Pietenpol going from a 65 hp Lycoming to 100 Corvair ponies. Here are some photos of the conver…

flycorvair.net

I’ve struggled a little bit with cutting a slot in my gear build so I’m ordering new material. In the mean time I’ve had lots of people reach out to me with ideas. This was sent to me this morning by a fellow Baby Ace builder. I must say, it’s very interesting. I’m actually considering it.

All opinions welcome.

 

[Vigilant1]

As WW mentioned, all the damping with this system comes from tire scrubbing ( not from the available damping that rubber bungees/doughnuts provide due to internal friction losses). That can work fine (as it does with Wittman-style gear legs), but it's not the same thing as the older system provides, particularly when not on dry, hard pavement. So, worth seeing how it actually behaves in practice.

 

[delta]

I don't know if anything off the shelf could be adapted, but the idea of hydraulic dampening apeals to me. Hydraulic Shock Absorbers | Reverse Loading | W-Technologies

 

[Marc W]

Doesn't Pops have die spring gear on the JMR?

 

[Little Scrapper]

I would think there’s two factors that are pretty important here. Pre-load and some type of adjustment. WW welded the ends on but a heim joint should work. 3/8” bolt to pin this on the structure so I’m assuming a Heim HM6M part number. Not sure what impact that would handle

 

[wsimpso1]

I like it. Use adjustable rod ends on at least one of them so you can always true it up.

 

[blane.c]

Threads break?

Might as well streamline it.

Can use a magnifying mirror to see the backside of slot when filing.

 

[TFF]

Acrosport uses springs, and I believe Dana rebuilt his old Starduster with springs. I think there is a thread.

 

[Little Scrapper]

Acrosport uses springs, and I believe Dana rebuilt his old Starduster with springs. I think there is a thread.

The WW gear in the article is very different from those other spring gears.

 

[proppastie]

Mooney Bungee....way too small but the design can be scaled up....WW is welded together and this design you would be able to take apart and change the springs etc.

 

[TFF]

Ok. I see the difference now. The normal type always works backwards to the bungee. That one works in the same direction. I think the only difference I would want is the short mount side have that tube go through the spring tube for alignment when sliding, but you would have to make a pivot at the axel. Probably needs one anyway with no give like a bungee can as the gear swings.

 

[Pops]

I used die springs on the LG of the SSSC and the main gear of the JMR. Spring from Dayton Progress. You have to work out the mechanical advantage of the gear to know the compression load on the die springs, ( not hard). Also need to know the travel and preload on the springs . I use a adjustable rod end on the top end of the strut to fine tune the strut length for my average flying weight so the wheels are vertical .
On picture 0051 you will see the gear is slightly tucked in with no weight. With my weight and fuel they are straight. Gear has a side load limit of 3150 lbs.
Picture of the main gear on the JMR. Same size spring of 6" long X 2"OD but stiffer for the heavier weight of the JMR over the SSSC.

 

[Pops]

Bearhawk with rod ends on both ends of the shock strut.

 

[egoman]

By the way the circle track racers have this product available every day of the week and it is adjustable. And it is available with many rates pf springs.

 

[Little Scrapper]

Bearhawk with rod ends on both ends of the shock strut.

What Heim joints do you use? HM6M? Which are 3/8”?

 

[Pops]

On the Bearhawk the plans shows a rod end that Bearhawk kit company sells. Plans show a rod end on the top. But due to the gear geometry, if built by the plans, there will be a bind somewhere in the gear travel at the bottom of the shock strut. We ordered the same rod end as used on the top and installed on the bottom of the strut to take the bind out. The rod ends used on the SSSC and JMR are smaller and I will check my notes tomorrow and let you know. I do remember ordering the rod ends from Aircraft Spruce.

 

[Victor Bravo]

By the way the circle track racers have this product available every day of the week and it is adjustable. And it is available with many rates pf springs.
View attachment 106826

Do you have a cost range for these? Is there a major supplier of this type of spring? Do they make these springs with rigid tubes coming out the end (so you have some sort of side-load resistance on an aircraft installation)?

 

[LittleBird]

I have never seen it done like this on an airplane but have seen this used in other machines. Look at what a Citroen 2CV or Ami uses for suspension. Same idea but with a rubber rebound damper.

 

[Richard Roller]

I've seen it on several Pietenpols. It seems to work fine.

 

[proppastie]

Do they make these springs with rigid tubes coming out the end (so you have some sort of side-load resistance on an aircraft installation)?

I really do not know however looking at the picture if the springs or disk compressing the springs are a close fit then there will be side-load resistance.....those die springs are really big wire..... if not one might add a close fit detail around the springs.....I have to wonder though if that is a shock rather than a bungee.....it does make a difference ....be nice to have a link