Jacks are Done - Fun Project!

[bigmo]

I've seen a few jack threads here and thought - I can do that! I wasn't super impressed with commercial options under $1K. It seems like one has to spend $1400+ to get something of decent quality. I spent a few nights drawing things out, sourced out my steel and spent a bunch of time looking at commercial designs to see what I liked. I started with a quality jack (Omega 4-ton) and then built the base and supports around that. Splurged a bit on good hardware and overengineered the steel a bit. I grew up on a farm, so I can do some crude welding, but paid my neighbor in beer to strengthen a few areas I could not get too well with my stick welder. I gave up trying to engineer a top solution to interface with my jack points, and decided to go with proper jack toppers (Bogert Aviation) so I never to have worry about slipping off the jack point. I could have cleaned up my welds and slag a bit more, but was frankly tired of drilling holes in cold rolled steel and just taped and painted it and called it done. I did have a booboo that turned out to be a cool feature. My magnet jig was not set to 90 degrees and I got one leg off by 3 degrees on both sets. I caught it early enough to solve my problem and add a leg adjuster on each jack (on one leg). It's a nice way to really stabilize the jack and not depend on an absolutely flat hangar floor. I have a cherry picker for the front, so gear and wheel maintenance from now on will be a non-event. $360 in materials and two cases of High Life...so $400 all-in.

 

 

 

 

 

 

 

[Z W]

Those look good, and stout.

Only feature you may be missing is a way to lock the jacks up so that you could leave the plane on them for an extended time without relying on the hydraulics. Some use a locking collar, something like this:

[bigmo]

@Z W Yes indeed! I actually have a set coming from Amazon today. 
Do you use the collars every time, or just when you know the plane will be on the jacks for an extended period?

Im going to put them each under a 1000 pound load and see if I get any loss after 24 hours.

[47U]

15 minutes ago, bigmo said:

Do you use the collars every time, or just when you know the plane will be on the jacks for an extended period?

What I do… if the airplane is on jacks overnight, I put on the collars.

[Utah20Gflyer]

I would recommend one small modification to your design. I would place one additional fastener where the 45 degree supports transition from being parallel to the 2x4 to the 45 degree angle.  Most of the strength of the design relies on those supports being placed in tension so that elbow provides slack when a side ways load is applied.   It doesn’t look like that type of support would do much in compression.  Anyway, I’m not an engineer but that is what I would do.   
 

They look nice, I have a similar project planned.  

[IvanP]

55 minutes ago, bigmo said:

@Z W Yes indeed! I actually have a set coming from Amazon today. 
Do you use the collars every time, or just when you know the plane will be on the jacks for an extended period?

Im going to put them each under a 1000 pound load and see if I get any loss after 24 hours.

EVERY TIME the plane is up on jacks, especially if the gear will go up. The O-ring can fail at any time and it could become really expenive really fast (prop strike and/or injury). It only takes a minute to lock the collar or put a safety bolt through the ram and it will prevent injury or damage to the plane.

Edited November 3 by IvanP

[MikeOH]

Every time I jack up my car I put safety stands under it.  Just because the jack supported 2,000 pounds overnight the last time...doesn't mean the cheap Chinese made O-ring won't fail in the next 30 seconds! Use the collars!

[Pinecone]

8 hours ago, Utah20Gflyer said:

I would recommend one small modification to your design. I would place one additional fastener where the 45 degree supports transition from being parallel to the 2x4 to the 45 degree angle.  Most of the strength of the design relies on those supports being placed in tension so that elbow provides slack when a side ways load is applied.   It doesn’t look like that type of support would do much in compression.  Anyway, I’m not an engineer but that is what I would do.   
 

They look nice, I have a similar project planned.  

Actually, I really don't like the flat straps with a bend to stabilize anything.  NO stability in compression

[Hank]

8 hours ago, IvanP said:

EVERY TIME the plane is up on jacks, especially if the gear will go up. The O-ring can fail at any time and it could become really expenive really fast (prop strike and/or injury). It only takes a minute to lock the collar or put a safety bolt through the ram and it will prevent injury or damage to the plane.

Amen, brother! I've seen pictures of Mooneys that fell off jacks and perforated the wing . . . .

[bigmo]

1 hour ago, Pinecone said:

Actually, I really don't like the flat straps with a bend to stabilize anything.  NO stability in compression

I was going to go thin square tube, but wound up using the 3/16" cold rolled bar. You would be shocked how much strength it took to cold bend those. I practiced on one throwaway and then was able to duplicate it without having to go back for adjustments. Based on some of the lightweight jack designs I saw, this is way superior. I'd not argue a square tube would have been better, but I wanted a design that I can service or replace the jack if needed. This was the only way I could achieve that goal without getting into a much more complicated project.

Remember that any lateral movement also has to contend with the opposite force on the other side. I obviously cannot calculate how much side stability this will support, but it's a lot. I see hangar neighbors with their jacks supported by conduit & hose clamps (and their plane hasn't suffered for it). I'd argue I have 50x that strength. For grins I flipped the hitch on my truck, and jacked it up and goofed around in the bed of the truck. Zero movement and a breeze to lift.

But, appreciate the feedback for my next design. If time were free, I'd have welded pads to the lateral support angles and then bolted the pads to the base.

[EricJ]

54 minutes ago, bigmo said:

I was going to go thin square tube, but wound up using the 3/16" cold rolled bar. You would be shocked how much strength it took to cold bend those. I practiced on one throwaway and then was able to duplicate it without having to go back for adjustments. Based on some of the lightweight jack designs I saw, this is way superior. I'd not argue a square tube would have been better, but I wanted a design that I can service or replace the jack if needed. This was the only way I could achieve that goal without getting into a much more complicated project.

Remember that any lateral movement also has to contend with the opposite force on the other side. I obviously cannot calculate how much side stability this will support, but it's a lot. I see hangar neighbors with their jacks supported by conduit & hose clamps (and their plane hasn't suffered for it). I'd argue I have 50x that strength. For grins I flipped the hitch on my truck, and jacked it up and goofed around in the bed of the truck. Zero movement and a breeze to lift.

But, appreciate the feedback for my next design. If time were free, I'd have welded pads to the lateral support angles and then bolted the pads to the base.

Yeah, it *looks* weak like it'd buckle under lateral load with compression on the bars, but if you used stiff stuff it's probably good.   They may be heavier than if you used tube/conduit or something like the commercial jacks, but that's a tradeoff.   Nicely done!

[Pinecone]

Also, like someone else mentioned, with the single bolt, there is slack for the tension side to not stop the jack from tipping.

[bigmo]

21 minutes ago, Pinecone said:

Also, like someone else mentioned, with the single bolt, there is slack for the tension side to not stop the jack from tipping.

I'll probably add a second bolt on all uprights. Honestly hand drilling through the cold rolled was way harder than I anticipated. The hot rolled channel is thicker and drills easy. That bar was unbelievably hard to get through. Luckily I have a whole jar of fresh 1/8" bits.

[MikeOH]

I guess I don't quite understand all the concern with @bigmo's design.  So what if the flat straps don't have relatively high compression strength?  Picture the lateral forces applied and you'll see the straps on the OTHER side will be in tension.  I don't think the jack cylinder is going anywhere when subject to a side load! Nice job, but way more work than I'm up for!

[EricJ]

52 minutes ago, MikeOH said:

I guess I don't quite understand all the concern with @bigmo's design.  So what if the flat straps don't have relatively high compression strength?  Picture the lateral forces applied and you'll see the straps on the OTHER side will be in tension.  I don't think the jack cylinder is going anywhere when subject to a side load! Nice job, but way more work than I'm up for!

Without the second bolt that he's talking about adding, if a strap goes in tension it can pull some length up off the bottom and allow the jack to tilt if the other side buckles under compression.    When he adds the second bolt it'll be better from that perspective.  

[MikeOH]

1 hour ago, EricJ said:

Without the second bolt that he's talking about adding, if a strap goes in tension it can pull some length up off the bottom and allow the jack to tilt if the other side buckles under compression.    When he adds the second bolt it'll be better from that perspective.  

LOL!  Yes, I considered delving into that 'fine' point.  So, let's consider that: how much length do you think that strap will grow in length if it is really put into sufficient tension?  Eyeballing it, maybe an inch? Attach point is maybe 18" up?  So, a 3 degree tilt.  Also, looking at the thickness and width of those straps, just how much force do you think 'stretching' that strap is going to take?  And where, exactly, is that much force going to come from?  No way the side load from the wing jack point is going to transfer anywhere near that magnitude before the wing just jumps off the jack!

Criticizing this overbuilt jack just seems awfully petty to me.

[Pinecone]

10 hours ago, MikeOH said:

I guess I don't quite understand all the concern with @bigmo's design.  So what if the flat straps don't have relatively high compression strength?  Picture the lateral forces applied and you'll see the straps on the OTHER side will be in tension.  I don't think the jack cylinder is going anywhere when subject to a side load! Nice job, but way more work than I'm up for!

But the side in tension has the bent part and some flat on the bottom piece that can lift up and allow the jack to tilt.

And the other side will bend more and not stop the movement.

 

[MikeOH]

1 hour ago, Pinecone said:

But the side in tension has the bent part and some flat on the bottom piece that can lift up and allow the jack to tilt.

And the other side will bend more and not stop the movement.

 

Yeah, about 3 WHOLE degrees, as I pointed out; not the exaggeration you depicted.

And, did you miss the part about how much ACTUAL force bending those straps is going to take? And, just where that amount of force is going to come from.

Honestly, I can't fathom why people just can't complement the guy for a nice job and leave at that.  This isn't 'constructive criticism', it's nit picking!

[Pinecone]

It is someone who does not want someone else's plane to fall off the jacks.   My depiction is how the braces will deform with a side load.  NOT the built in angle you ended up with.

No, I have not calculated the force required. But it will be a lot less than a better design.  As to where that force will come from is the 2000 or so pounds of airplane.  It everything stays straight, all will be well.  Once something starts to bend, all bets are off.  Like standing on an empty soda/beer can.

 

[MikeOH]

50 minutes ago, Pinecone said:

It is someone who does not want someone else's plane to fall off the jacks.   My depiction is how the braces will deform with a side load.  NOT the built in angle you ended up with.

No, I have not calculated the force required. But it will be a lot less than a better design.  As to where that force will come from is the 2000 or so pounds of airplane.  It everything stays straight, all will be well.  Once something starts to bend, all bets are off.  Like standing on an empty soda/beer can.

 

I guess I'm bored so let's continue with how absurd this idea that the 'plane is going to fall off the jacks' over these straps is!

I'm not talking about any 'built in' angle.  I was talking about how much force would be required to bend the straps to deform them enough for the straps to 'straighten out' causing the jack to tilt.  That would result in no more than a 3 degree angle; once the straps are straight there is no more tilt to be had!

The plane weighs 2,000-3,000 pounds.  That force is divided by two for one jack, 1,500 at the most.  But that force is acting DOWN, not at an angle.  Now something pushes sideways on the plane causing a side load.  The question becomes is the side force which going to push the jackpoint off the jack less than or greater than the force which will BEND the straps enough to cause the jack to tilt far enough that the plane 'falls off the jacks'?  A 3 degree angle of tilt would represent 75 pounds of force for a 1500 pound vertical load.  No way 75 pounds is enough to 'straighten out' those straps, and even if more force is applied to where they did straighten, 3 degrees isn't going to be enough to cause the airplane to 'fall off the jacks'.  Further, the force has to be enough to not only straighten the strap in tension, but collapse the other strap in compression; I doubt 75 pounds is enough to even do that!  Hence, your analogy to crushing a beer can is false; once a critical angle is reached the compressive strength dramatically DECREASES and the can collapses.  In this case even if the force is great enough to straighten the straps, once reaching 3 degrees the strength INCREASES.

You want to criticize the design with the altruistic claim of "do not want someone else's plane to fall off the jacks" but don't want to do any reasonable analysis or calculations to support that criticism?

[Pinecone]

I see your point.  But again, the design could be better.

If you are happy, then great.

 

[Kelpro999]

14 hours ago, Pinecone said:

But the side in tension has the bent part and some flat on the bottom piece that can lift up and allow the jack to tilt.

 In defense, it’s a design feature that allows lift point tracking during seismic activity.

[Joshua Blackh4t]

Great work, looks nice.

And yeah, in a physics textbook that bolt isn't optimum, but real life it will never let you down.

The bolted base is interesting, did you drill that out or were there holes there? I think most I have seen used supports around the edge rather than bolts.

Anyway, here's to many uneventful times using them. 

[Flyler]

Now that you went through all that effort, you're going to arrive at your plane to see it on your own jacks with your rims stolen 

They look great to me. 

[Joshua Blackh4t]

13 hours ago, Flyler said:

Now that you went through all that effort, you're going to arrive at your plane to see it on your own jacks with your rims stolen 

They look great to me. 

Don't you lock your rims away at night? Thats the main reason they fold up, right?