McCall Hitch Shock Question

[Grassy]

I have a McCall Hitch. Would like to swap out the 4 shocks before we go on a long haul later this year. They don't look like they need to go but since we will be on the road for almost 6 months, better safe than sorry.

Are they a special sort of shock like for class Cs or can I use a right length car shock ?

I am swapping out the shocks on my 5th as well and found that auto shocks would actually hurt my trailer.

Unfortunately, McCall hasn't been around for awhile even though there were rumours that his son was manufacturing them again. I looked at the design sheet and the orgin of the shocks is not mentioned.

Would these work ?

http://www.shockwarehouse.com/site/product.cfm/id/19160/name/555025-Monroe-RV-GasMagnum?gclid=EAIaIQobChM

[Ronbo]

Aren’t there any numbers on the shock? If not, measure the collapsed and extended lengths. 

[Grassy]

I don't see any so I need to pull one off. I will be doing that later this week.

Hopefully there will be a number that I can follow up on..

 

thanx

[phoenix2013]

For all you "newbies" and lurkers, a bit of history.

McCall hitch is the granddaddy of all RV air hitches, designed and built way before it's time. Gene McCall was a real pioneer in the RV field. His company, Square D in New Mexico, did the first conversions of MDTs to RV Haulers. At that time it was discovered that commercial trucks, like MDTs (and later HDTs) are brutal on the flimsy frames of RVs. Gene was a brilliant engineer and a fabricator (I had a pleasure of meeting him in New Mexico) and he designed the McCall air hitch for his MDT conversions. What is brilliant is that he not only designed an air hitch but also designed into it an anti-chucking feature. Those two horizontal airbags can be "tuned" to the weight of the trailer to reduce that incessant tugging back and forth while puling trailers (fifth wheels in particular). Along the way  somehow he met Jerry Clark. I'm assuming it was for business reasons and not friendship. The reason I say that is because McCall had to tell Jerry to stop building the hitch on the account that Gene McCall had a patent on it, oops! I had a chance to review the patent, pretty strong.

Jerry doesn't give up easily so he designed TrailerSaver and with his aggressive marketing essentially out-muscled Gene in the marketplace. And that's too bad because until ET showed up, there has not been any anti-chucking hitch on the market for 20 years.

Jerry built a very successful business and he and his partner sold TrailerSaver to it's current owners. Both signed non-compete agreements, I know the partner. However, there is Comfort Ride hitch, Jerry's new "invention", which functionally is about as close a knockoff of TralerSaver as possible. The pattern continues.

 

Edited June 19, 2018 by phoenix2013

[Grassy]

Phoenix,

Excellent recap.

Did he use standard auto shocks on it ?

Thanks..

Edited June 19, 2018 by Grassy

[phoenix2013]

I don't know, when I met Gene it was a social visit, he was pretty much retired.

From a technical point of view in an air hitch the shock absorbers don't do much. The forces involved are massive and the sizes of  shocks that can fit in the available space only allows for small piddly shocks with not much excursion and therefore effectiveness. That's why I didn't bother with shocks on ETs and instead I use polyurethane shock absorbers that can produce 1,000s of pounds of resistance in a very small space   

There are many tables on google, like this one   http://www.lunghd.com/Downloads_and_Links/2005_productshock_spec.pdf that you can use to determine the how to match what you have to what you can replace it with.

Curious, how you ended up with this hitch, these are like gems, not too many around?

[Grassy]

Phoenix,

Thanks you.. time to go into research mode with the shocks.

I attribute the acquisition on serendipity. When I bought my truck,  my truck it had a ball hitch on it.   The last owner pulled a race car trailer with it. Before him, it pulled a boat. He had this hitch and he knew nothing about it ( i did) and I had him toss it in with the sale.

My rig is a mystery. I have done much research on it as I can and I only stopped when I started hitting brick walls.  After it was shipped to a high volume Freightliner dealership,   it disappeared for months until it reappeared at Beaudry RV for sale new.  Freightliner has no idea where it went.  I think Sport Chassis did the work while it was still owned by Freightliner but cannot confirm. Records are not that good and i think there were a lot of conversion companies that have disappeared.

I have looked at many other conversion companies ..I see some similarities but nothing exact. It isn't a biggie for me but I am curious.

Regardless, the hitch looked like it had very little use and I am impressed with it.

 

[phoenix2013]

Match the shocks so that they are the same size, have the same travel and mounting scheme and don't worry about it. It's the hitch and the airbags that do most of the work. That hitch was indeed a rare Rolls Royce of hitches in its time.

What size and weight trailer are you pulling with the hitch and do you play with the horizontal bags inflation to optimize the anti-chucking?

[Grassy]

I have a 31.5 foot Arctic Fox that weighs in @ 12K.

When I installed the hitch, I put the horizontal and vertical air bags on different zones.

I haven't been able to find any literature on inflation rates so with some playing, I normally run 40 in the vertical and 60ish in the horizontal.

I run about 100 psi in my rear tires but thinking when we head out for the long run, I should go a bit higher. I have Michelin on it with a bit softer sidewall. I did weigh everything when I first got it and used the inflation tables for the tires to come to those numbers.

Am I off ? 1.. always seeking to do better.

As for the shocks, I will install 4 identical units.

Thanks

Ian.

 

[Morelli]

Looking at those "shocks" (actually dampers)  in small size, I would start with the dampers used on truck cabs.  When I updated by hitchcrafter hitch to reduce bounce, I used freightliner cab dampers, they where the ideal size and length for what  i wanted to do and copied McCall's placement and worked out very well !!

You will have better luck searching for Cab Dampers vs Shocks ....  Lots more information comes up and you will find the smaller sizes.

 

[phoenix2013]

I'm not aware of any "table" how to set this hitch up, sounds like you are "about right". Looking at the bags (and I know a lot about them) the verticals are probably 2.000 pounds each and the horizontals 2,500 pounds each (that's at 100 psi max pressure and they are linear).

So at 40 psi you are supporting about 1,600 vertically and the horizontals have 1,500 pounds against each other. Incidentally your fifth at 12K is absolutely "perfect" for that hitch, when Gene designed his hitch "substantial" fifths (32-36 feet) were running 8,000-13,000 GVW. If you arrived at the campground in a 35 footer everything stopped and you got the "looks of envy".

I would guess your pin-weight might be around 2,000 pounds and considering you are getting some pressure from the front bags and the head being about 1/3 of the way to the hinge 40 psi on the rear bags seems about right. Is there any line or indication of the ride height, etc., on the hitch?

60 psi in the anti-chucking bags seems to me a bit high. We measured chucking at one time developing trailer brake controller (with an 8K fifth).

and normal chucking is only few hundred pounds back and forth and it's constant. Big "chuck" you see above was with very aggressive braking and with good trailer brakes OK controller, it's about 1/3G which in your case would be about 4,000 pounds. I don't know what the actual compression in the center point between the bags is and how they react against each other with a chuck, I would experiment with that pressure by lowering it in stages (50 in each, 40 in each) and see if you can detect "relaxation" in you neck muscles in normal pulling. I'm assuming when you pull you drive very defensively and brake gently. When we saw the 1/3G that was on an empty road, we clamped the hammer down hard and went from 50 mph down to zero in three seconds.

[Grassy]

Wow. You have given me more quality info that I have been able to find.

No.. no indicators but I came to that number (40) with having the 5th level . I understand that a level trailer tows/handles the best.

We are careful drivers.. we keep it just under 65 and with the height of the cab, are able (on the most part.. had one surprise)  to gauge and adjust to what is happening in front of us. We were in Quebec once and running at speed around a corner and ran into a parking lot. Hard on the binders and all was ok.

I had wondered about the 60 number so I will start dropping it. Comfort and safety are our goals..

I *appreciate* your advice.
Thanks.

[Grassy]

19 hours ago, Pug said:

Looking at those "shocks" (actually dampers)  in small size, I would start with the dampers used on truck cabs.  When I updated by hitchcrafter hitch to reduce bounce, I used freightliner cab dampers, they where the ideal size and length for what  i wanted to do and copied McCall's placement and worked out very well !!

You will have better luck searching for Cab Dampers vs Shocks ....  Lots more information comes up and you will find the smaller sizes.

 

I shall look into this...I want to pull one of the existing units and to take a look..

[noteven]

Grassy - take a look at Canadian Loadshare’s website for the in cab control used on their air spring kits. It allows you to set and hold a certain air pressure from the drivers seat. It might be useful on the chucking section of your McCall. It is a control that is also used on lift axles. 

[MarcMcCall]

On 6/19/2018 at 11:25 AM, phoenix2013 said:

For all you "newbies" and lurkers, a bit of history.

McCall hitch is the granddaddy of all RV air hitches, designed and built way before it's time. Gene McCall was a real pioneer in the RV field. His company, Square D in New Mexico, did the first conversions of MDTs to RV Haulers. At that time it was discovered that commercial trucks, like MDTs (and later HDTs) are brutal on the flimsy frames of RVs. Gene was a brilliant engineer and a fabricator (I had a pleasure of meeting him in New Mexico) and he designed the McCall air hitch for his MDT conversions. What is brilliant is that he not only designed an air hitch but also designed into it an anti-chucking feature. Those two horizontal airbags can be "tuned" to the weight of the trailer to reduce that incessant tugging back and forth while puling trailers (fifth wheels in particular). Along the way  somehow he met Jerry Clark. I'm assuming it was for business reasons and not friendship. The reason I say that is because McCall had to tell Jerry to stop building the hitch on the account that Gene McCall had a patent on it, oops! I had a chance to review the patent, pretty strong.

Jerry doesn't give up easily so he designed TrailerSaver and with his aggressive marketing essentially out-muscled Gene in the marketplace. And that's too bad because until ET showed up, there has not been any anti-chucking hitch on the market for 20 years.

Jerry built a very successful business and he and his partner sold TrailerSaver to it's current owners. Both signed non-compete agreements, I know the partner. However, there is Comfort Ride hitch, Jerry's new "invention", which functionally is about as close a knockoff of TralerSaver as possible. The pattern continues.

 

Old thread but this is quite right. The shocks are Monroe shocks that were sold through Napa. I don’t remember the exact part #. I built the first air glide hitches In my grandfather’s shop. This image is the very first prototype ever built. 

 

Edited April 9, 2019 by MarcMcCall

[phoenix2013]

2 hours ago, MarcMcCall said:

Old thread but this is quite right. The shocks are Monroe shocks that were sold through Napa. I don’t remember the exact part #. I built the first air glide hitches In my grandfather’s shop. This image is the very first prototype ever built. 

 

Mark, good to hear from you. Your grandfather was quite a character, but more importantly he was an innovator and a pioneer. In 2009 we were on a 11,000 miles cross-country trip when were introduced to Gene by the then President of the MDT group.

That's me on the left and Mrs. on the right. You probably remember these two pictures.

Your grandfather was pretty much retired by then, but he was still "sizing me up", particularly when he learned that I had a prototype hitch in my semi that had anti-chucking built-in and NO it did not violate his patent. That's when I learned about the shenanigans between him and Jerry.

Edited April 9, 2019 by phoenix2013

[MarcMcCall]

Hey Phoenix. Thanks for the reply. Sounds just like the old man sizing you up. I learned a lot from him in the short few years I worked with him. I think things would have went a lot different had he spent more time on marketing back in the day. The internet wasn’t quite what it was back then as it is now. Guys like Jerry back then had a leg up when it came to that and knowing how to use it. I’ve had often thoughts about trying to start the hitch building back up over the last few years and see where it goes. The patents are long lapsed, but all the dimensions are still in my head. I like to check the net from time to time to see what’s been posted over the years. when I came across this post it makes me feel good to have been a small part of it for the time I was. I still have a firm belief from what I’ve seen out there the hitch is still quite remarkable and knowing he was an innovator of the whole market of today from back then. 

[phoenix2013]

 

 

Being an engineer and a designer, I appreciate things that are well thought out, on point and frankly ahead of their time, the McCall hitch was certainly that in its time. I notice things that to others might appear odd or inconsequential, like the head mounting shaft (front to back) not being horizontal but slightly angled up (or down depending which way you look), why? To re-align the chucking force vector of the trailer coming forward and "bend" that vector more into the anti-chucking air bags. Bravo. Your grandfather also understood that hitch incorporating anti-chucking technology is a must since mitigating these forces is as important as cushioning the up and down movement and force vectors.

Before I designed an ET Hitch, I've been RVing for about 30 years, mostly in pickups and then for a few years in MDTs. I hated the literal pain in the neck from chucking particularly on long cross country trips, which would get worse as the size and weights of my trailers got bigger and heavier over the years. So, the weights of the trailers got bigger, but the weights of the pullers I was using remained relatively the same (around 7,000 pounds). The heaviest trailer I owned when pulling with pickups was 12,500 pounds so there was already almost 2:1 imbalance in favor of the trailer. People routinely pull 18-22,000 pound trailers these days behind pickups, that's 3:1 or even more, I can only imagine what the chucking is in these setups.. If you could make in-roads into that market you should be able to carve out significant chunk of it and I can guarantee you it would be a "grateful chunk", in spite of the fact that such a hitch would be invariably more expensive than the likes of B&W, Curt and other "chuckers".

The ET, like McCall was designed from the onset with an anti-chucking technology. It took me couple of weeks of pondering over different schemes until I came up with the  dual parallelogram arrangement. I knew I could design the rest of the hitch but that part was most "intellectually  challenging". It has been a very successful hitch over the last decade. As you can see from this thread,  

I recently "arranged" for the hitch to be manufactured and sold by a very capable manufacturing outfit which will assure it's existence well into the future. Their manufacturing technologies and machinery is something I could have only dreamed about, certainly the quality will go up and manufacturing cost will come down. You might want to consider to perhaps partner with an outfit like that.

Couple other cautionary "suggestions". I beefed up the ET couple of times over the last 12 years in response to heaver and heavier trailers. You might want to "review" the original design in that regard. Also, it is my understanding that the Binkley head is no longer offered by Holland to hitch makers. Trailer Saver has a copy of it made in China which they make for their use only. I designed my own head years ago in order to cut that "reliance string" and the fact that the Binkley heads reached their "capacity" and were wearing out much quicker with the 20K+ trailers.

 

Edited April 11, 2019 by phoenix2013

[MarcMcCall]

19 minutes ago, phoenix2013 said:

 

 

Being an engineer and a designer, I appreciate things that are well thought out, on point and frankly ahead of their time, the McCall hitch was certainly that in its time. I notice things that to others might appear odd or inconsequential, like the head mounting shaft (front to back) not being horizontal but slightly angled up (or down depending which way you look), why? To re-align the chucking force vector of the trailer coming forward and "bend" that vector more into the anti-chucking air bags. Bravo. Your grandfather also understood that hitch incorporating anti-chucking technology is a must since mitigating these forces is as important as cushioning the up and down movement and force vectors.

Before I designed an ET Hitch, I've been RVing for about 30 years, mostly in pickups and then for a few years in MDTs. I hated the literal pain in the neck from chucking particularly on long cross country trips, which would get worse as the size and weights of my trailers got bigger and heavier over the years. So, the weights of the trailers got bigger, but the weights of the pullers I was using remained relatively the same (around 7,000 pounds). The heaviest trailer I owned when pulling with pickups was 12,500 pounds so there was already almost 2:1 imbalance in favor of the trailer. People routinely pull 18-22,000 pound trailers these days behind pickups, that's 3:1 or even more, I can only imagine what the chucking is in these setups.. If you could make in-roads into that market you should be able to carve out significant chunk of it and I can guarantee you it would be a "grateful chunk", in spite of the fact that such a hitch would be invariably more expensive than the likes of B&W, Curt and other "chuckers".

The ET, like McCall was designed from the onset with an anti-chucking technology. It took me couple of weeks of pondering over different schemes until I came up with the  dual parallelogram arrangement. I knew I could design the rest of the hitch but that part was most "intellectually  challenging". It has been a very successful hitch over the last decade. As you can see from this thread,  

I recently "arranged" for the hitch to be manufactured and sold by a very capable manufacturing outfit which will assure it's existence well into the future. Their manufacturing technologies and machinery is something I could have only dreamed about, certainly the quality will go up and manufacturing cost will come down. You might want to consider to perhaps partner with an outfit like that.

Couple other cautionary "suggestions". I beefed up the ET couple of times over the last 12 years in response to heaver and heavier trailers. You might want to "review" the original design in that regard. Also, it is my understanding that the Binkley head is no longer offered by Holland to hitch makers. Trailer Saver has a copy of it made in China which they make for their use only. I designed my own head years ago in order to cut that "reliance string" and the fact that the Binkley heads reached their "capacity" and were wearing out much quicker with the 20K+ trailers.

 

My hats off to you sir. I've seen this hitch (ET) over the years (web images and articles) and only now putting name to person as we've now just conversed personally. As I stated I just check the web from time to time as it pertains to the RV hauler industry I once worked in with my grandfather in. I'll admit he was a brilliant man for his time innovating the hitch. As with anything times change and things progress. Trailer weights, larger trucks, etc..... The knowledge I took from my days working with him building hitches and trucks to building off road vehicles incorporating 4 link suspensions systems I saw where your "dual parallelogram" has geometrical benefits. 

I can relate to the manufacturing benefits to having an outfit capable of producing a product with precise tolerances. One of the major issues we had during manufacturing was building parts interchangeable from hitch to hitch. When I first started working for my grandfather every part was laid out, cut, drilled and manufactured by hand. I spent the good part of a year making jigs to not only speed up the process but help make the tolerances from part to part tighter. They were still a far cry from a "production line" part, but much better than each individual part being measures, cut, drilled being measured by tape measure and marked with a line or center punch and then cut or drilled to even having templates to cut radiuses with on the bag plates and shock mounts. 

I seriously doubt my thoughts of ever bringing the hitch back to life and manufacturing them again will ever come to fruition. I have neither the money nor resources  to sink into it to fulfill such an outlandish dream. Had I, the first 2 things I would do would be source it out to someone capable of building it so parts were made true to spec and repeatable and expand upon one of the sayings my grandfather used to use. Build it tough enough to haul a freight train but smooth enough to haul a Model A. Third would be to do such as you and design/build a new head. I saw some major flaws coming with the heads of the day as you stated. I knew back then the trailers were only going to get bigger and heavier so the hitch itself would need to get beefier parts built with different materials and the head as it was was only going to prove sufficient to a short extent. The materials weren't going to prove as a long lasting item. Cast parts just don't seem to have the life of something made from superior steels and proper machining. 

[Grassy]

Since I seem to be the last known  user of the McCall hitch I will continue the story. I have tried to find others that are using in but no joy.

last summer, I blew an air bag on the back of the hitch.  Had to repair it on the road..  and best guess between the repair dude and me is that the rear airbags were too large.  All I knew about this hitch before buying it was that it sat in a lot of garages and was passed on when the truck was sold... and unfortunately, I did not keep the rear bags when I replaced them.

I get home from the trip and the same airbag has been abraded but not worn through.  That is why I asked about shocks .. they seems , in retrospect, pretty dead to me. My truck has been a massive learning curve for me.  

I replace that bag again and the shocks. And, I nipped away at some of the material in the bar that did the damage.  And yes, I used Monroe shocks...glad I got that right. Oh, I had to increase the pressure a bit to lever the 5th wheel.

Last November we headed to Texas. Pa and Ny had rough patches ..but La  .. wow..  anyone has driven through there knows how rough it is. All is good with my hitch.  Coming into Houston we were diverted off the interstate and we were hauling through back roads far faster that was comfortable with the local LEOs urging us along when I hit a whopper.  I didn't know then but I snapped the welding on one shock and nipped bag.  Found out later when I was checking the bags that we nipped that bag again but Carl (member here) , who was beside me, noticed that I had broken a shock. He and my son, helped me fix that shock and re attach a slider on the unit. I did order a spare but in the mean time, I put a piece of duct tape over the abrasion as an early warning sign to replace the shock.  

In January, we left Mission Tx and headed west along the Mexican border. We then toured Nm  and went into Az as far as Tuscon. Back to Nm (Roswell, white sands)  the up the west side of Tx on secondary roads then across to Texarkana into Ar. Then back through Maine.  The hitch was solid with zero rubbing on the duct tape. 

I can only conclude that the shocks are multi purpose..not only to slow doing the up/down for/aft movement but also to prevent the hitch from destroying itself.

Would love to talk with someone who uses this hitch..

I will say that it gets a lot of attention with the folks that understand hitches...for an 18 year truck, it gets a lot of attention too. 

We cannot make the HDT rally but we head back to Tx in November.

 

Cheer, Ian. 

[noteven]

Keep in mind everyone that air “bags” are springs and want dampening (“shock absorbers”) in order to not function like undamped springs (pogo stick). 

Back to the experts....

[phoenix2013]

5 hours ago, noteven said:

Keep in mind everyone that air “bags” are springs and want dampening (“shock absorbers”) in order to not function like undamped springs (pogo stick). 

Back to the experts....

I had some fun in this thread running a "class" on airbags and suspensions (starting on page 3)

I stopped the "education" just before discussion of shock absorbers and dampeners (even though I promised to "continue") looks like I need to come up with that "installment".

Edited April 12, 2019 by phoenix2013

[Grassy]

Please.

And if you can, do something on air pressure in the tires.

I bought a tmps last summer and have been absolutely fascinated with what has been happening with the tires while running and with the warm / cold temps we have experienced.  I have asked a few questions on several boards and from the range range in responses, it seems that pressures and when to fill are a mystery to all.

Now that I am home, I had planned on  contacting Michelin and for an explanation.  I run 6 steers on my TV and 4 Lts on my trailer.

With all you work on bags / springs..have you studies how air pressure affects them  ?

Ian 

 

[phoenix2013]

Hmm, good to have "scientist" in the audience. Air pressure vs. temperature is governed by ideal gas laws, specifically by Gay-Lussac's Law  http://www.1728.org/gaspres.htm    you can also look up Boyle's Law and Charle's Law. These gentlemen lived in the Renaissance period where pursuit of science and scientific discoveries flourished.. I'm curious to imagine how the future generation will view the 21 century, where the leading "scientist" currently is an unemployed bartender. Perhaps I shouldn't dismiss the notion too quickly, a deeper study of cow flatulence and methane, it's major component could result in discovering a fourth ideal gas law and show us how ignorant we were.    Here's a good video and explanation air vs. temperature phenomenon .

Another "problem" relating to this phenomenon is in the world of sport, remember the "inflate gate", they have a calculator for that.

Football inflation vs. temperature http://physics.bu.edu/~schmaltz/deflate.html

I'll better start working on my next installment with all the scientific minds on this forum, just kidding, I'll get it done.

 

Edited April 12, 2019 by phoenix2013

[WDR]

I have this very same hitch on my truck. 

And I have the original instructions for it.

I'd be glad to help out .

Bill Rivard