Peace of mind under a Maxjax

[52wrench]

Hi,
First time poster, great website. I thought you'd like to see what I did to mine to get rid of that uneasy feeling of it cratering in when I'm under it. I had 4+ inches of concrete and the anchors all went in fine but this eliminates any concern. The main tube is 3" 6061 .125 wall tube. The outer tube is 3" sch. 40 pipe that is a slip fit over the main tube. This is set up so I can use it with my lowered 911. The 911 floor pan is about 5" off the ground so the top of the tube can't be over that, I set it at 4". That put the bottom of the tube below the bottom of the carriage so I added a piece of 1/4 plate to the carriage so the tube has full bearing. I will have to make custom adapters for the 911 so the pad is not more than 1" below the jacking points, otherwise the tube will hit the sills or pan before the pad contacts the lift point. The dimensions between the posts have to be even top and bottom to prevent any binding as the lift is raised. To use it the car is positioned then the tube is slid under the car and put into the short collar then other collar is slipped over the two bolts on the carriage plate and the pin is inserted to lock it.

 

[52wrench]

Also here's an easy way to make sure your holes are straight. A piece of DOM welded to a plate makes a simple and effective drill guide. I just spotted each hole right thru the base plate with the 7/8 bit. Had to clean up a few of the holes in the base plate with a die grinder so the bit wouldn't hang up. But then the hole layout is perfect, no chance of the bit wandering.

 

[404]

Good job and very clever. The spleen that does not get squished may be your own.

 

[52wrench]

Thanks. It will make me feel better under my 5700# pickup. You could put a hinge between the base plate and the floor and it still won't crater with this although I don't recommend that.

 

[rconnon]

Interesting idea. I like it.

I'm not an engineer, but wouldn't this put extra load on the carriages? as a car/truck is lifted the carriage has some room to move in the post channel, and depending on the weight / position of what you're lifting the posts can flex slightly, would this transfer load to the other carriage unnecessarily?

I totally get the peace of mind, I've had my lift for over a year, and still get nervous. That's with 7+ inches of concrete, over spec'd lift for what i'm lifting, 7" Hilti anchors and all 12 anchors holding their torque with no issues.

I even thought of a way to secure the top of my columns to the engineering beam in my ceiling, then i start to think, am I being overly paranoid?.

 

[CNGsaves]

Great idea OP !!!

Do you install before lifting . . . . or after once vehicle is up in air ??

Get the parts streamlined and welding/assembly down to a science and you've just created a sideline business for group sale on GJ !!! . .

 

[Cobra96]

Greg Smith Short Jack Stands For added safety.

 

[tc-cad]

Ingenuity.............it's all over this website. Great idea. That's what I would do.

TC-CAD

 

[52wrench]

Keep in mind I haven't used it yet! But I used some online calculators to determine the engineering critical buckling load for a 96" aluminum tube of this OD/ID and that gives about 12500 lbs. That assumes it is pinned at each end, if you assume it is clamped at each end then it goes up to about 29,700 lbs, meaning you could stand the tube up straight and center 29700# on it if the column was attached to the load and floor. As for making them to sell, no thanks, I'm not a big fan of personal injury lawyers, HAHA. The collars at each end don't have to be made of aluminum, steel would be fine if you don't have a TIG. To use it you put the car where you want it for the lift then slide the the pin collar on the close end of the tube, slide the tube under and put the far end into the small collar,slide the pin collar back onto the two bolts on the carriage plate and then insert the pin to lock it. For my 911 I'll probably have to leave the left rear arm off until I get the tube into position and then install the arm. I have to make some custom adapters for the lift pads before I can try it. As for putting more load onto the carriages or posts I could see that happening if you don't have the posts parallel top to bottom. The tube could try to force the carriages/posts apart if the tops were closer together than the bottom and pin holes were drilled with the carriages at the bottom. I actually made some sheet metal shims to get my posts perfectly parallel. I am going to do some more calcs to see what the actual compressive load is on the tube with 3000# on each pair of arms at full extension. Use this idea at your own risk.

 

[1969]

Personally, I think that is a super idea. If I had a Maxjax, I would use that in a heartbeat.

 

[lakeroadster]

Keep in mind I haven't used it yet!

That's a good thing!

While I certainly condone creativity I just have to ask:

• Has there been a history of Maxjax failures that would make you think this is needed?
  
• Are you worried about anchor bolt failures?

Food for thought:

1. Don't do the cross bar. If you are really this concerned it sounds like maybe you would have been better off buying a 4 post lift.
   
   
2. If you are dead set on using the cross bar, redesign it to be loose. Make the cross bar short and slot the retaining holes. This allows the lift to operate normally and there will be no binding. If there ever is an anchor bolt failure the lift will move some, but then the cross bar will engage.
   
   That being said, what's your plan to restrain the lift from fore and aft movement?
   
   If there is any binding you are totally changing the loading on the Maxjax components. And you have altered their design, which means you are now responsible for any issues

 

[52wrench]

No, no history that I'm aware of, I'm sure Dannmar doesn't publicize it if there was any failures. No, not worried about anchor bolt failures, there is over a 3:1 SF built in to their anchor design, I reviewed there design calcs before I bought it. If I wanted a four post I would have bought one, I wanted a two post that was moveable. My posts are parallel so there won't be any binding, no need to shorten the cross tube. No plan to limit fore and aft movement except a jack stand under each end of the vehicle. The moments applied to the post and base plate by the vehicle trying to "crater in" are far greater than that of the vehicle's COG not being perfectly centered fore and aft. I have to laugh on the last line, I've been altering designs since I first picked up a wrench, about 50 years ago.

 

[lakeroadster]

Sounds like you have it all figured out.

So why are you altering the design of a brand new lift?

 

[ClineWrench]

Not that I'm smart enough to have figured out what 52 wrench has already figured out, but I can answer the question of why alter. Brand new lift: it's because the newest greatest stuff can always be improved. That's why there is newer and greater things later down the road.

For all we know, 52 wrench might call Dan,ar and pitch his plan to them for a royalty. Personally, I would refine and patent the idea, then sell the patent to Danmar for. Decent sum plus royalties on future unit sales.

Personally, I think it's a great Idea.

 

[52wrench]

Sounds like you have it all figured out.

So why are you altering the design of a brand new lift?

Because I want to. If designs were never changed we'd still be driving Model A's and using outhouses.

 

[lakeroadster]

Because I want to. If designs were never changed we'd still be driving Model A's and using outhouses.

Actually if they never changed, we'd be riding horses or Model T's not Model A's.

I drive both of the later, I highly recommend them...





You might want to think about my suggestion in regard to making the cross brace loose... Your design may well create anchor bolt failures.

Happy trails to you in any event. Good luck with your adventure.

 

[Vegaman_Dan]

Seems like this bar would get in the way of the very reason to have the lift in the first place- access!

I've not heard of failures of the lifts, and usually when you do read or see stories about lift failures, it's not the lift, but the way the vehicle was loaded that made it unsafe. The vehicle ends up tippling off the arms. Underbody stands can fix that issue readily. Most stands are too tall, but it wouldn't take much to shorten them to be useful for a MaxJax. It's something I want to consider when I use mine for vehicles again.

 

[52wrench]

"You might want to think about my suggestion in regard to making the cross brace loose... Your design may well create anchor bolt failures." Only if the posts aren't parallel, but I might take an 1/8 off. Very nice rods, can you run them there w/o fenders? Talking about adventure, I was in CO this summer on my adventure bike (Yamaha XT1200), gorgeous state. I went from Doyleville on I-50 north to the WY border 95% on the gravel. Crossed many passes, just stunning scenery, only dropped the bike once walking it thru a rock garden going up Hagerman Pass. I was only unsure of where I was a few times, and that was with a GPS.

 

[savethatclassic]

Anyone thinking about running a cable to the walls studs, just as a safety measure.

What I did is had my floor redone and added a 15inch footer with where the hoist will be, then I'll use the kit MJ sells, those epoxy anchors are like 6 inches long, cant see how they could ever rip out.

 

[lakeroadster]

Very nice rods, can you run them there w/o fenders?

Sure. Land of the free, home of the brave. Your question makes me wonder, where do you call home?

Anyone thinking about running a cable to the walls studs, just as a safety measure

Unless you want to pull the stud out of the wall, and maybe pull the wall down too, that's a bad idea.

 

[52wrench]

Yeah, I wouldn't tie it into the structure unless you want to pull that down to if the lift ever failed. Re. where I'm from, western New York state, the land of taxes and corrupt politicians. Thinking of leaving it soon, getting real tired of the BS.

 

[davejo]

I was looking at my floorplate type lift (not max jack)and thinking of how things might fail.
i'm thinking of building a crossbeam up high for it or cable tethering it to the 6 by 6s that are on either side to keep the tops of the columns from tilting inward or fore/aft. (polebarn)

When you say "crater in" you mean the upright starts tipping inward because the concrete breaks at the toe of support and the anchors pull out of the heel of the baseplate? Your tube keeps the upright vertical as the concrete collapses or does it protect the toe concrete from collapse-inducing forces, or both?

 

[firworks]

Yeah, I wouldn't tie it into the structure unless you want to pull that down to if the lift ever failed. Re. where I'm from, western New York state, the land of taxes and corrupt politicians. Thinking of leaving it soon, getting real tired of the BS.

Your lift has already failed, things couldn't get much worse. Might as well bring the whole place down. If you survive you'll get a fat check from non-stop Fox's "When Buildings Collapse" for the footage.

<iframe width="420" height="315" src="https://www.youtube.com/embed/nL39q9cl5T0" frameborder="0" allowfullscreen></iframe>

Back on topic, I do think you'd probably be better off not rigidly mounting your cross bar. There's always going to be different loading inwards and outwards of the column for each side of the lift as a car isn't uniform homogeneous load. I'm sure the pillars are designed to be able to handle that and will move slightly to compensate. You want your cross bar to prevent deviation beyond a certain critical limit, but you don't want it to prevent all inward/outward motion. Similar to structural designs for anything seismic. You really don't want it to be super rigid, you want it to be able to move safely within limits. I could very well be talking ***-outedly but it would make sense to me to keep that bar but find a way to mount it with some amount of movement for adjusting to the load.

 

[WVBrady]

...
Back on topic, I do think you'd probably be better off not rigidly mounting your cross bar. There's always going to be different loading inwards and outwards of the column for each side of the lift as a car isn't uniform homogeneous load. I'm sure the pillars are designed to be able to handle that and will move slightly to compensate. You want your cross bar to prevent deviation beyond a certain critical limit, but you don't want it to prevent all inward/outward motion. Similar to structural designs for anything seismic. You really don't want it to be super rigid, you want it to be able to move safely within limits. I could very well be talking ***-outedly but it would make sense to me to keep that bar but find a way to mount it with some amount of movement for adjusting to the load.

When I put my K-10 pickup on my MaxJax, the columns flexed enough to put some sideways pressure on the lockbars, so that I had to tug on them to remove them, prior to lowering the lift. After the lift was lowered, I put a level up against the columns and they had returned to perfectly vertical.

 

[rburke65]

lake roadster...... How will would this cause anchor bolt failure?

 

[lakeroadster]

lake roadster...... How will would this cause anchor bolt failure?

By forcing the uprights to follow the owner installed cross rail, in the event they are not parallel with each other.

The lift mechanism was designed to be loaded from the weight of the car only, the cross bar, (if rigid) induces lateral thrust loading the lift was never intended to see.

This would put high lateral stresses on the sliding lift mechanism, as well as other parts of the lift, including the anchor bolts.

Take the design to extremes and you will understand my point. Assume the span of the columns are two inches narrower at the top than they are at the bottom. When you lift the vehicle it is trying to spread the rails apart, this induces very high loads on the anchor bolts.

Without the cross bar the arms simply slide on the vehicle frame...but with the cross bar everything is locked solid, which is not the design intent of the lift.

 

[LS6 Tommy]

I can appreciate 52's concern and applaud his execution. That setup works for a 911, but for me the point of putting the car up in the air is to work underneath it. That crossbar would hamper doing transmission or exhaust work on a front engine, rear wheel drive vehicle.

Tommy

 

[52wrench]

"When you say "crater in" you mean the upright starts tipping inward because the concrete breaks at the toe of support and the anchors pull out of the heel of the baseplate? Your tube keeps the upright vertical as the concrete collapses or does it protect the toe concrete from collapse-inducing forces, or both?"

No, the concrete is not to going to collapse, the baseplate wants to pivot on the inside edge and pull the anchors out. Is it necessary from a pure theoretical standpoint? No, if the anchors are installed correctly. Dannmar's design calcs show that each anchor has a rated pullout strength of 12580 lbs. and with 3000 lbs centered on each pair of arms the total tensile load applied to the five anchors is 11668 lbs. So that is a SF of over 5:1. Another way of looking at it, one anchor in the center rear position should theoretically hold the rated load. They say the actual yield strength of the bolts/anchors is 20,806 lbs avg, that's where the anchors pull out or the concrete around the anchor fails. So from a pure design standpoint it's not necessary assuming you have 3000 psi concrete and the anchors are installed correctly. It cost me $100 in material, is it worth it to have a better feeling when under it? For me it's a no brainer. Kind of like wearing a seat belt, the chances are slim you'll ever need it, do I feel better with it on , absolutely.

 

[Denwood]

This should definitely not be used during a lift...only after. Lake has a very good point with regard to parallelism of the posts and stress that could be imparted. Another consideration is that the hydraulic flow divider Maxjax uses is not perfect, so a difference of 1.5 inches in lift height is within their spec. Your cross support should be designed to account for this difference. Ideally you would only install your bar after a vehicle is lifted. On the other hand, your cross bar may very well "help" with equalization, and during a hose failure (providing it can take a few thousand pounds of tension) may very well bind up and add a level of safety. In that scenario though you would end up with one post potentially loaded to twice it's design capacity. If I was doing finite analysis on the system, I'd want to look at the one hose fail scenario.

Likelihood of a properly installed Maxjax failing at the mount bolts is very small, due to the engineering over-design that has occurred. The only failures that I've seen reported on the Maxjax (two of them on GJ) is a hose failure during a lift, causing one side to drop. Because there are no ladder locks, it would make sense that a hose failure (while the lock bars are out) would the largest risk during a lift or lower. For my own peace of mind, I used epoxy anchors, and re-poured a 14" deep 3'x12' slab for the lift.

My take on safety while lifting was to purchase four of the Gregsmith low rise stands. In place, and tensioned, the stands can take virtually all bolt loads off the lift, in all directions and add an extra safety net under the vehicle.

In terms of the hose failure scenario during lift/lower, adding an adjustable velocity fuse at each piston base seems like the best idea. I'd love to see Maxjax sort out a mechanical ladder lock.

52, kudos for trying something new, and sparking a good discussion

By forcing the uprights to follow the owner installed cross rail, in the event they are not parallel with each other.

The lift mechanism was designed to be loaded from the weight of the car only, the cross bar, (if rigid) induces lateral thrust loading the lift was never intended to see.

This would put high lateral stresses on the sliding lift mechanism, as well as other parts of the lift, including the anchor bolts.

Take the design to extremes and you will understand my point. Assume the span of the columns are two inches narrower at the top than they are at the bottom. When you lift the vehicle it is trying to spread the rails apart, this induces very high loads on the anchor bolts.

Without the cross bar the arms simply slide on the vehicle frame...but with the cross bar everything is locked solid, which is not the design intent of the lift.

 

[Serj_DMR]

Hey Guys,

So we have been watching this thread as it’s definitely something we want to address and make clear our stance on this matter. This modification, while on paper looks good, can lead to unforeseen issues. As Dennis pointed out, the unit will function just fine if installed correctly as long as you do not go over the 6000 lb. weight capacity. As this unit sits right now, if an issue were to occur, we cannot be sure if it was an original issue or if the unit was stressed into failure by the modification. Unfortunately, this would void your warranty as that loading lakeroadster talked about may stress not only the slide blocks and frame, but the motor and fittings, etc.

We cannot stop you guys from making modifications and sometimes you all come up with some pretty clever stuff, but at the end of the day, we have spent a lot of time coming up with the design and there have been no failures as it relates to "cratering". The only scenario this would happen in is if there was an inadequacy in the concrete strength or installation of the anchors themselves. To further my point, attached is a photo of a HMMWV (Hummer) on a MaxJax. I have talked to this customer and he has had ZERO issues with his install so far. Standard anchors and all.

In closing, safety is our number one priority. If you have any questions or concerns, please feel free to PM me or call us at 877-432-6627.

Have a great new years!

-Serj
Dannmar® EQUIPMENT

 

[Serj_DMR]

Let's try this again! The photo:

 

[52wrench]

Thanks for your input, I figured you'd chime in sooner or later. Please tell me how it is going to over load anything if the cross post is installed after the vehicle is at the desired height and it is removed before it's lowered? That's how I've decided to use it just to remove any chance of binding even though my posts are absolutely parallel and there is enough play between the tube and collars to handle any difference in lifting rate between posts. I agree on the safety part, that's why I built it, since I'm the one with 5700# over me.

 

[turbodave]

Greg Smith Short Jack Stands For added safety.

Yep, these are what I use with my mid-rise lift for added safety

http://www.gregsmithequipment.com/2-Ton-Tripod-Stand-SHORT

They should be a good height for maxjax users also

 

[lt1driver]

does increasing the floor to 4-5000 psi rating help any ??

 

[sac02]

Yep, these are what I use with my mid-rise lift for added safety

http://www.gregsmithequipment.com/2-Ton-Tripod-Stand-SHORT

They should be a good height for maxjax users also

Same here, with a scissor lift.

FWIW, I'm an engineer at an automotive OEM, and our OSHA/ISO/Whatever acronym approved approach is the same: tripod supports (but the full sized ones). Nobody is allowed to lift a truck without them, period. Our facility has one of the lowest safety incident rates in the industry, BTW - sometimes I hate the safety nazis, but I can't deny they generally have good practices in place.

Modifying a lift is foolish, plain and simple. Unless you have the engineering knowledge to design your own lift, tacking parts on to someone else's lift is a bad idea. Tell us, are you familiar with a free body diagram, and did you work any numbers for your mod? Or did you just add some metal, because "more metal always makes things stronger"? Hint: It doesn't.

 

[52wrench]

"FWIW, I'm an engineer at an automotive OEM"

LOL, is it VW? Maybe GM and you were on their ignition switch team? How about Ford and their Powersmoke 6.0? Chrysler transmission team? BMW and their diesel heads that plug up? Honda airbags?

I tell you what, you do your FBD on a two post lift with a cross bar and the same lift w/o a cross bar and tell us which one has greater resistance to post bending moment and anchor pullout. It doesn't take much more than an eighth grade education to figure that out.

BSME and MS here, entirely capable of designing my own lift.

"and did you work any numbers for your mod?" Obviously you didn't read the thread.

Hint: Don't tell people you're automotive OEM engineer, you'll get a lot more respect.

 

[Johns12]

I just don't see how there would be a problem using the bar after the car is lifted, then removing it before lowering as the OP said.

I'm not an engineer

 

[lakeroadster]

Hey Guys,

So we have been watching this thread as it’s definitely something we want to address and make clear our stance on this matter. This modification, while on paper looks good, can lead to unforeseen issues. ....

In closing, safety is our number one priority. If you have any questions or concerns, please feel free to PM me or call us at 877-432-6627.

Have a great new years!

-Serj
Dannmar® EQUIPMENT

Thanks for posting on this thread. A lot of companies just sit back and won't comment... it says a lot about Danmar that they offer their insight / opinion.

Hint: Don't tell people you're automotive OEM engineer, you'll get a lot more respect.

Look in the mirror. You just lost a bunch of respect with that comment. Really, WTF?

 

[James E]

Thanks for posting on this thread. A lot of companies just sit back and won't comment... it says a lot about Danmar that they offer their insight / opinion.

Realistically, what other comment would we expect? Whether a customer's mod is good or bad, the manufacturer would NEVER, EVER, EVER publicly state that the mod is a good idea. There is no upside from the business' perspective in saying that.

I do think, however, that it's always a good thing when a company monitors forums like this and lets us know that they are listening.

 

[Serj_DMR]

Realistically, what other comment would we expect? Whether a customer's mod is good or bad, the manufacturer would NEVER, EVER, EVER publicly state that the mod is a good idea. There is no upside from the business' perspective in saying that.

I do think, however, that it's always a good thing when a company monitors forums like this and lets us know that they are listening.

James,

Thanks! We do our best to take feedback seriously as we are not omniscient and can always improve things in one capacity or another. I can at least pass the feedback up the chain!

Thanks for your input, I figured you'd chime in sooner or later. Please tell me how it is going to over load anything if the cross post is installed after the vehicle is at the desired height and it is removed before it's lowered? That's how I've decided to use it just to remove any chance of binding even though my posts are absolutely parallel and there is enough play between the tube and collars to handle any difference in lifting rate between posts. I agree on the safety part, that's why I built it, since I'm the one with 5700# over me.

52wrench,

I can understand that sentiment completely. I also would do everything in my power to prevent accidents or issues with my install. That being said, I have been under a vehicle on the MaxJax numerous times. I trust the engineering and our warehouse floor. It works as my photo shows with a 5,800lb hummer on the lift.

As I said previously, we cannot stop you guys from making modifications and I do genuinely laud the creativity and engineering. That being said: I cannot, as the OEM, advise that you continue with any modifications. Again, even only using it once locked in place, it looks good. But it's not the original design.

Hopefully you find peace in using the lift as intended. As always, feel free to reply or call the main Dannmar line for more info.

-Serj