Drawbar receiver modification to move drawbar outward.

[Jerry_NJ]

This is an update of a 1 year old thread I finally took action on. But I till have some questions - I can include a picture but think it doesn't provide anything I can't handle in worlds.

Old thread is:
http://forums.iboats.com/forum/gene...-towing/644422-draw-bar-and-receiver-pin-size

Today I took a step drill, the largest I have, to enlarge the 1/2" locking pin hole in the drawbar to 7/8" so I could lock my new higher up-step drawbar.

First, I was surprised how quickly and easily the step drill enlarged the hole. It took no more than a couple of minutes per side to enlarge the hole.

Second, now I wonder how much the modification compromises the strength of the tow connection. This modification moves the draw bar outward a bit over one inch (I can measure but distance is the standard spacing on drawbar receivers), leaving about 2 1/2" inside/behind the lock pin hole.. The drawbar has the usual loose fit, i.e., one can wiggle the drawbar a slight amount.

I think (can check) that my 2" drawbar arrangement is designed for trailers up to a couple of tons and for a tongue weight of up to 200 pounds, maybe more. My application is foe a 15" aluminum boar with a 9,.9 HP engine. I'll estimate the trailer at well under 1,000 pounds and the trailer tongue weight is under 100 pounds.

Does anyone have experience or ideas on the risk of a breakaway that may exist for the modification? This modification was discussed in the above referenced thread, and no one there expressed a concern about strength of the modification. Not trying to pass the responsibility off to anyone, but if anyone has experience or concern I'd appreciate reading it.

Thanks,

 

[smokeonthewater]

We covered this in great detail already..... It was suggested that you not modify the hitch... you insisted so we told you how to do it.....Of course there is a possible danger... To determine what it is you would need an engineer to study the modifications and probably have to do some destructive testing on several prototypes.

 

[Jerry_NJ]

Thanks, I didn't expect to get any guarantees... maybe just someone who "got away with it". I plan to give it a try, albeit I plan only short towing on mostly level smooth roadways. I have two lakes within 7 miles of my house. I will inspect after a few pulls to see if I can see any damage to/around the bar/receiver.

 

[smokeonthewater]

The info you are asking for is totally worthless.... I have a buddy who (much to my disdain) 'get's away with' driving drunk regularly and I used to have another friend who is now dead because someone else didn't 'get away with' driving drunk.... the experience of the first guy doesn't cancel the experience of the second.

You are taking at least some risk with your safety and that of everyone else on the road because you choose to make modifications but you don't have the qualifications to determine whether they are safe... MAYBE the risk is close to zero and MAYBE it's pretty high... nobody here can acurately tell you.... sure you may find a few to say they are sure you are fine and maybe a few to say you'll kill people for sure but none of them would have no way to actually know what the claimed to know.

Please understand that I am not suggesting that you are or are not doing something on the same level as driving drunk.... Just the first example that popped into my head

 

[bruceb58]

Why not get a longer drawbar? I guess I must be missing something.

 

[bigdee]

I might be missing something here but...you now have the correct size pin securing the drawbar so I don't see why you have a problem. Sure,you have moved the drawbar out 1 inch but what would that matter as long as you have 4 inches inserted into the receiver? You are pulling a very light load anyway.

 

[Jerry_NJ]

Thanks, Bigdee.....it is nice to know I'm not alone in my thinking. I in fact recall, but have not gone back to read, that the discussion on this topic that resulted from my post a year ago had several advocates of simply drilling out the 1/2" stabilizer hole to allow passing a 7/8" (standard) locking pin through that hole to lock in the drawbar, albeit a inch, maybe inch and one half, shallower into the receiver. The drawbar is still 4" into the receiver.

The reason for doing this was to raise my tow connect, and the large "step" drawbar is really built to drop, but may be used "upside down" to raise. Problem is the reinforcement on the drawbar going to the ball level hits the bumper before the supplied holes line up when installed "upside down". So, the danger of my modification may be offset somewhat by getting the trailer into a safer towing level. It also allows me to raise and lower my trailer jack (dual wheel) when the trailer is connected to the truck. I notice too that the new height is at the level if I used the Chevy Colorado step bumper hole. I think the bumper connection has less strength than my modified 2" frame connected receiver/drawbar arrangement.

I looked first for a 2" receiver extension -- they are available but I didn't purchase one for whatever reason.

Yes, my engineering (an electrical not mechanical or structural and retired too) estimate is the tow arrangement I have is way over engineered load wise for my application, even a 50% reduction in strength is still more than needed for my load.

I plan to give it a try, and I will use more than my usual safe driving style to give extra room between me and other "out in the country" traffic. I will not be towing any faster than 50 mph and for no more than 4 miles at that speed. Otherwise driving below 40 mph.

So whatever I learn will not directly apply to someone towing at 70 mph down an interstate.

 

[frantically relaxing]

The sheer strength of a simple 1/4" bolt is nearly 8,000#, your 7/8" pin's strength is around 140,000#. The metal around your new hole will be the weak link. Unless the hole is real close to the back of the bar, I doubt you have any worries towing a 15' boat around...

 

[Jerry_NJ]

Checking a few of my numbers, I see the standard lock pin is 5/8" not the 7/8" I noted in my original post.

My Drawbar is rated at 6,000 load and 600 tongue weight, or about 10 times what I am loading it with. The enlarged hole (was 1/2", increased by 1/8") has lots of metal before the end of the receiver, a couple of inches and the walls of the receiver must be at least 1/4" steel.

Happy we "talked" this through. I now feel very confident my modification is a safe tow arrangement, and would be even if I hooked up to a fiberglass boat weighing twice what my Discovery 14' weighs. This boat is decked out like a "bass boat" so a lot heavier than a simple 14' aluminum.. It weighs too much for me to man handle it on dry land if I get it loaded a little off center.

Also, I learned the step drills I have cut very fast, it was in fact easy to enlarge the 1/2" hole using a step drill. I think the hole would have been much rougher if I had purchased a 5/8" drill, an expensive drill.

 

[smokeonthewater]

step drills are 'DA BOMB' lol... I don't know what I ever did without them and my Iphone..... loss of either would be too much to bear LOL

 

[Jerry_NJ]

Test run worked out fine. I took my Discovery boat to the lake yesterday, Sunday. The first trip this year, ouch! There was a big event, bike and running race at that lake, the water was low (no concrete launch ramps) and windy, so I went to another lake which caused me to use an interstate for about 5 miles at 65 mph. Overall my usual 5 or 6 miles to a lake came out closer to 12 miles oneway, and 6 home. The drawbar held up fine, not indication of any handling or wear problems. As noted the hitch is way "over engineered" even with the modification I put on it.

 

[bigdee]

Test run worked out fine. I took my Discovery boat to the lake yesterday, Sunday. The first trip this year, ouch! There was a big event, bike and running race at that lake, the water was low (no concrete launch ramps) and windy, so I went to another lake which caused me to use an interstate for about 5 miles at 65 mph. Overall my usual 5 or 6 miles to a lake came out closer to 12 miles oneway, and 6 home. The drawbar held up fine, not indication of any handling or wear problems. As noted the hitch is way "over engineered" even with the modification I put on it.

Great!. Now you need to relax and catch up on boating before cold weather sets in!