How is a Tow Bar supposed to work?

[TonyMac]

My buddy and I did the same with his TR8 on a tow dolly. Seems the Triumph tranny also gets lubed by the input shaft. $5000 lesson to always check first, but maybe dolly tow with the rears up.

[RogerSmalley]

I agree with most of the comments concerning your custom fabricated base plate. I see no evidence that the designer did much more than figure out a way to get the car and the coach hooked up. Are you aware of any other baseplate fabrication that this person made that was successful?

Were measurements taken from a similar Blue Ox baseplate? I'm not sure that there is much variance in the spacing between the attachment points of the tow bar to the car. The crossbar that one contributor mentioned sets that distance and reinforces the bar geometry. Whether or not a crossbar is needed is determined by the baseplate designed for that car. The fact that there is not a Blue Ox baseplate for your car is a big bright red flag. My suggestion is that you take your car and coach to a shop that installs baseplates regularly and ask for their opinions. They might decline to help you out for reasons of liability, but it's worth a try.

Manufacturers of tow bars and baseplates, like Blue Ox and Roadmaster (now Demco) know where the design problems are and how to make their equipment safe on the highway. Any baseplate you design for your car should mimic in construction, dimensions, and interface the design of the one that matches your tow bar . That might mean starting fresh with both a new tow bar and a Blue Ox baseplate that could be modified slightly to fit the frame components of your car. You'll void the Blue Ox warranty on all of their equipment by doing so, but you would be at least starting with equipment that is designed to work together.

Through that process you might figure out why there is not a Blue Ox baseplate for your car. If so, perhaps it would be more wise to buy something that is towable. See the annual lists of towable cars published by Motorhome magazine and Family RVing published by FMCA. Their websites have archives of those annual lists going back several years.

You said that the car key is in the ignition. Is it in the "on" position to free the steering wheel? Is the battery disconnected to prevent discharging and other possible damage?

In the end You might find that the best way to travel with your Beemer is to use a tow dolly or a suitable trailer.

[oharris]

I'll give you my 2 cents as someone who has fabricated their own tow bar mounts for a jeep and never had a design related problem in 20 years. I've had lots of other problems towing but I've never lost the jeep nor have I damaged the attachment points.

If you can bend your mounts that easily just by having the tow bar out of level and going around a corner then they are too weak. Yes it appears to have been fixed by leveling out the towbar, but you may find yourself in a position where you have to go around a corner with the towbar pointing up or down due to the terrain, and they're just going to bend again. I would add some sort of gusset to prevent that and then test it by setting it up with the towbar at an angle like it was when you bent it before. Stuff happens when flat towing and you want your mounts to be strong as possible.

The point about having the safety chain mounted seperately from the towbar attachment is a good one. Perhaps the gusset would be a good place to attach the chain. If those 2 bolts were to back out or break I would want the safety chain to still be attached. I have fortunately never had to test my safety chain mounting, but if the bolt holding the towbar to the mount were to break or fall out, my chain would remain attached.

With respect to the transmission, it sounds like you have successfully towed the car on a dolly without problem, but have you considered what affect the angle of the car on a dolly has on lubricating the output shaft? That may be the difference between it being fine and causing damage. i think if it were me I would check the temperature of the transmission frequently on the first trip of any distance or highway driving. (As an aside, why not continue to use the dolly since that was working for you?)

I thought I was golden on my jeep since the transfer case output shaft was completely submerged in oil. It turns out that the spinning shaft inside the stationary gear pumps all the oil out of it at high speeds and eventually does damage. I have heard of jeeps catching fire while being flat towed. I started disconnecting the driveshaft any time I was going to be on the highway for any length of time and eventually went to a full floating rear axle with lockouts to solve this problem.

It's all a learning process when it comes to fabbing and operating your own stuff. (For instance, if you drive the car with the towbar upright, make sure it's tied up, you don't want it falling while you're driving, ask me how I know.)

Good luck!

[CntryCoachRV]

Originally Posted by bamaboy473

By the way, the proper term is, "Jerry" rig, a nod to German soldiers doing everything they could to keep their equipment working in the waning months of WWII........

It's still early morning, and you've already learned four things

Hey Bamaboy, it all depends on who you ask!
https://www.merriam-webster.com/word...-usage-history

[soberskier]

Originally Posted by bamaboy473

I inherited a Blue Ox tow bar when I bought the coach, and have recently completed fabricating a base plate, and installing an Invisibrake system, so ready for the road test! hmmm, not good.

The right base plate tab bent down about 60 degrees. I straightened it out and tried it again, but the tab bent with the car being towed out of the driveway (right hand turn). Here is what I noticed:

The arms on the tow bar lock in the extended position and stay that way. Is this the way they're supposed to be?

The hitch height is 16" and the tow eyes are 11" high. I thought I read that a 6" difference was acceptable, but is this correct?

Any other causes of high stress while turning?

Consider purchasing the correct "baseplate for your model toad.

And yes the arms should lock in place.

[aether_one]

Originally Posted by soberskier

Consider purchasing the correct "baseplate for your model toad.

And yes the arms should lock in place.

And where would he make that purchase? You have about 88 more posts to read in this thread.

[Mark 7]

The only thing I would like to contribute here is that engineers make mistakes. We see it all over in the farm equipment world where equipment falls apart and they come up with upgrades and ways to stiffen certain areas of high stress to make toolbars stay together. In some cases we do mods ourselves where there was an obvious oversight.

Weather or not I would build the OP's matchup the same way, he is thinking. I can see some ways I might have done it differently, but I tend to overbuild things. The point is, he is seeking help from various entities and making his plan come together from trial and error, and doesn't seem to be getting a lot of encouragement here.

I have built 5 trailers of various sizes, the largest being a 30' gooseneck flatbed with a beavertail. I had it inspected by the state and it passed so I could get it titled and licensed. There are probably a lot of engineers (armchair and otherwise) who would tell me what I did wrong on that build. I found out myself I had to make some improvements in places, but after 30 years and 2 rebuilds it is still on the road and better than ever.

I recently rebuilt the hitch that is on the back of my Montana because I didn't like the way the PO had installed it. The next owner may not like my setup and build it again (but I doubt it).

I think instead of excoriating the OP and asking him his route so that "I am not anywhere near that latchup" offer a little advice and encouragement, let him absorb it all... and move along!

[BD104X]

The fact that no one makes a baseplate for the OP’s car doesn’t mean it CAN’T be towed, it just means the manufacturers realize that enough people aren’t looking to buy one to make it worthwhile for them to develop one. I will say that it doesn’t sound like the OP did enough research to determine whether or not his can be towed.

[mikeh2obury]

Originally Posted by bamaboy473

I inherited a Blue Ox tow bar when I bought the coach, and have recently completed fabricating a base plate, and installing an Invisibrake system, so ready for the road test! hmmm, not good.



The right base plate tab bent down about 60 degrees. I straightened it out and tried it again, but the tab bent with the car being towed out of the driveway (right hand turn). Here is what I noticed:



The arms on the tow bar lock in the extended position and stay that way. Is this the way they're supposed to be?



The hitch height is 16" and the tow eyes are 11" high. I thought I read that a 6" difference was acceptable, but is this correct?



Any other causes of high stress while turning?

What year and model is your BMW?

[dickb46]

Rick, I only read 5 pages of this so I'm really sorry if i'm repeating someone else.
I drug a 85 318 around for many years (on a tow dolly).
I have a factory Blue Ox base plate on our 96 Escort we tow now. That steel is not plain ole steel. It's hardened and the baseplate goes back to attach to solid frame(not the bumper).
I'm thinking if you keep up this effort your are going to twist the front end of your BMW completely out of align.

dick

[Hwy Hometime]

Yes...to summarize I too was questioning what works. I have to list my learned knowledge:
1st)the angle of the attached tow bar matters a whole bunch

2nd)a cross bar support is a must joining the toad base plates

3rd)the safety chains should be mounted else where from the base plates and this in my observation could be challenging

4th)the base plates should be at least 24" apart, hoping that the frame rails that they attach to allows this separation distance(new knowledge to me)to help with triangular strength of tow bar

5th)testing with a truck the performance of the apparatus would not help in the evaluation of the whole installation as the RV overhang is going to throw your happy with your creation test into deep woods disaster(my own opinion)

6th)not all standard transmissions can be flat towed(super observation)I for one never thought of front or non engaged gears being the lubrication key to a splash lube style transmission(Thank You for that one)

7th)braking hard may send the toad looking for a place to hide under the RV AND acceleration adding another stress onto the tow bar never mind the stress of cornering sharply

8th)much appreciated as I also fabricate my own parts where ever I can and my precautions to do it right matter to me a LOT.....NOW shoot me if I am out of line here but 7 pages and nearly 100 posts, Please Why.

I do not post much but I read lots and it's not my forte to spend this much time reading posts that contribute nothing but gibberish. Sometimes it is humors but mostly not. This was a good thread I have learned Thank You. I used to read a lot of Hot Rodding Forum and a very knowledge member that as they say forgot more than I know noted that IF YOU have a question to aid in your problem READ ALL RELATED posts FIRST then if you can't find a solution that has already been hashed to death several times then post using proper educate and knowledgeable people are more than happy to help.

This is a very well constructed forum, happy to be a leaned member