How Strong Does My Tongue Need To Be? (Mark 2)

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How Strong Does My Tongue Need To Be? (Mark 2)

Postby angib » Mon Apr 10, 2006 11:54 am

Some of you will remember that after Dave Nathanson's tongue collapse, I tried to come up with a tongue strength guide, though it never got very far.

So I am delighted that Adam ('eski') has pointed me to the Australian small trailer design rules - these contain a rule on 'drawbar' (tongue) strength that is dead simple to use and I have made up a web page with all you need to check your planned or existing tongue:

How strong does my tongue need to be?

If you want a sneak preview, here is a table that shows the maximum trailer weight (GVWR, not bare weight) for typical tongues sections and lengths. The web page shows you how to calculate the exact answer for your particular trailer.

Image

If you are Mike, you'll notice that your favourite A-frame 2" x 2" x 3/16" is good for a 2,300lb GVWR trailer with a 36" tongue. Whereas some other people here may have a nervous look to them.....

Incidentally, I've done the calculations for Dave Nathanson's trailer details and his trailer tongue had only 71% of the strength required by these rules - so that more or less supports the rule.

All comments and suggestions gratefully received.

I think it's great to have something definitive on tongue strength, rather than just everyone's (including my) experience or opinion, so:
Thanks, Aussies!

Andrew
Last edited by angib on Tue Apr 11, 2006 5:30 am, edited 1 time in total.
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Postby SteveH » Mon Apr 10, 2006 11:58 am

Andrew,

That's great...even I can understand that. :thumbsup:
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Postby Miriam C. » Mon Apr 10, 2006 12:13 pm

Andrew, and Aussies
Thanks. That matches pretty close to what mine says.

Need that for the next. 8)
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Postby mikeschn » Mon Apr 10, 2006 12:17 pm

Excellent Andrew...

Thanks,

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Postby asianflava » Mon Apr 10, 2006 1:06 pm

:shock: I guess I'll have to cut a foot off my tongue.
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Postby Miriam C. » Mon Apr 10, 2006 1:29 pm

:whistle: :rofl: :rofl: :rofl:
I guess I'll have to cut a foot off my tongue
.

So---Asianflava---How many feet do you have on your tongue.

(couldn't resist)

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Postby asianflava » Mon Apr 10, 2006 2:14 pm

I probably wouldn't have to if I'd quit sticking my foot in my mouth. :roll: Actually, I have to get the final weight before I do any surgery.
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Postby surveytech » Mon Apr 10, 2006 3:56 pm

Heres's something interesting.
The TSC trailer has a single 3' long tongue that is 2" x 3"x 1/8" and has a stated capacity on the sticker of

GVWR = 1500 LB
GAWR = 2000 LB.

looking at the chart above the maximum capicity of that tongue is 1240 lbs. at 36 inches long.

Do you think that means that Carry-ON is putting too light and tongue on their trailers?

Hey I am just curious.

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Postby angib » Mon Apr 10, 2006 4:58 pm

surveytech wrote:Do you think that means that Carry-ON is putting too light and tongue on their trailers?

Well, it would seem that the Carry-On trailers wouldn't meet the Aussie rule.... Actually I did a quick number-crunch on one of the Carry-On trailers a while ago and satisfied myself that while the tongue is quite beefy, the two angles it's attached to are not - they are likely to fail well before the tongue itself does.

Actually, I think this Aussie rule is pretty severe, but for amateurs that may not be a bad thing. When we've all been building trailers for 20 or 30 years, we'll be able to trim down the tongue strength quite a bit.

I hope Cary posts here, as I suspect the Camp-Inn wouldn't pass this rule either - though I don't have the spec of the frame members, so I don't know for sure. From what Cary and his customers have said, I doubt there is any problem with the Camp-Inn and so it is an example of where a general rule doesn't cover all cases.

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Postby angib » Mon Apr 10, 2006 5:05 pm

asianflava wrote::shock: I guess I'll have to cut a foot off my tongue.

Well..... I was going to add a comment about your trailer after I wrote about Mike's 'built like a brick outhouse' frame spec. But I felt it would have been a bit thoughtless to discuss it without involving you first.

Please give the details of the calculation for your trailer - you've obviously driven it a fair bit and it hasn't fallen apart, so it is another valuable data point.

I have long suspected that Dave Nathanson's trailer, at 71% of rule strength, only collapsed because of fatigue after being driven on washboard roads. Now this may be something that the Aussie rule is designed to avoid, but another option is to not drive at speed down washboard roads!

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Postby surveytech » Mon Apr 10, 2006 5:19 pm

It would be interesting to compare the two Harbor Freight trailer tongues.

Anyone have the sizes?
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Postby Chris C » Mon Apr 10, 2006 5:19 pm

My trailer tongue is 2x3x14ga and the A-frame is 2" anglex14ga. Right now the tongue is 51".....but that is without coupler. (figured I'd wait to weld that on later) Where would it fit on the chart?

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Postby PaulC » Mon Apr 10, 2006 6:36 pm

Hi Chris, with your build I think you have just blown those calculations right out of the water. If you ever need to carry a Mack on that you should be okay :lol: :lol:
Regards Andrew's comments about washboard(corrugations) roads, we have more dirt roads than bitumen over here. Plus our bitumen roads are second rate when compared to those in the USA. Hence we need to make sure with any specifications on trailers.
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Postby Cary Winch » Mon Apr 10, 2006 7:08 pm

Andrew,

Ok, I will post on this. Pretty simple, the load calculations used in that chart have no bearing on teardrops designs. Purely for utility trailers for which I agree they look correct. The load on a utility trailer does transfer to the tongue much more substantially. This is what I always have been saying about teardrop frames. They are not utility trailers and using info for building utility trailers will always garner you a extremely over built and heavy frame on a teardrop. The tongue does not see those kinds of loads on a tear. The tongue weight would have to approach those figures not the total weight for that to be correct.

A utility trailer has to support it's full weight at all points of the deck. If you put the full load all the way to the front of the deck (you know someone will) it will put ALOT of load on the tongue. This is why the chart makes sense to me. Now, a teardrop's primary weight is fixed to the station locations of the components used in the body. So, all you have for variables is loading inconsitancies of equipment.

The tongue on a teardrop has to do two things. Support the tongue weight while travelling down the road and drag the axle down the road behind it. I believe the straight pull capacity of two 2 x 2 angles is near 10,000lb. So, you won't pull the tongue off if it is welded on proper, even at the angle of a a-frame. I would figure probably 2Gs worth of shock on the tongue would be safe, correct me if I am wrong there it is a WAG. That being said a proper tear that weighs 1,000lb would have 125lb tongue weight. So, it would only need to take about 250lb. The chart shows that you would have to get out past 4' of tongue on the 2 x 2 a frame for it to get close to limits. Throw in extreme loading variables of lets say 50% and your tongue length would be pared down to something like 3' (like ours)according to the Aussie chart. This is where I see the chart being usefull if this is kept in mind.

Once again I am sure I am doing my rambling, my apologies. I might not even being making sense, I do that alot.

Once thing we did different in our teardrops is we built in flex. The body to frame joint is allowed to flex in front so that the tongue has some bounce. That seems to do a super job of absorbing road shocks. There is no sign of wear and tear on our frames, and we have done some pretty exciting stuff (well Craig mostly).

I wasn't aware of Dave's tongue failure. Can't comment on that.

Cary
Last edited by Cary Winch on Mon Apr 10, 2006 7:23 pm, edited 1 time in total.
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Postby Cary Winch » Mon Apr 10, 2006 7:19 pm

Andrew,

By the way, great webpage on this. Very usefull.

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