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

[asianflava]

: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've only driven it about 400mi, I'm not finished skinning it so I haven't had it weighed. My guestimate is probably around 800Lbs fully laden. The frame is 2"X2"X1/8" square tubing with the tongue extending 48in from the body. The reason the tongue is so long is because I was going to install a tongue box, after I put it together I thought it would stress the tongue too much (seems bouncy). The reason I kept the current length is because allows easy access to the rear of the SUV, cutting a foot (even 2ft) wouldn't be that big of a deal. I have been leery of the setup (bounciness) so I have a contingency plan if I see any noticible deflection. I can will a strap to the bottom (like Dean's). Even though I'm sitting at 1 Dave, I feel that no holes in the tongue (didn't Dave's tongue break at a hole?) and no offroading will prolong it's longevity.

When the cooler in the rear is full of drinks and ice, the tongue weight is pretty light. I towed it like this and it was stable at 80mph. I don't have any definite numbers on the weights but I hope to get those in a month or so, when I get it tagged. I'll keep you informed.

[bledsoe3]

Andrew, You and the Aussie's forgot one

[angib]

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

Anyone have the sizes?

I agree.

Though I would say I've been asking here for that info for about a year.....

Andrew

[angib]

My trailer tongue is 2x3x14ga and the A-frame is 2" anglex14ga. Right now the tongue is 51".....but that is without coupler.

Sheesh - in every group, there is always one........

OK, I've now modified the charts to include 14g tubes, but you'll need to go to the web page to see all the possible sections. Your frame design is a perfect example of what I've called a 'composite tongue', so the strength has to be checked in three places.

I would add 2" to the bare tube lengths to get the approximate length to the centre of the hitch ball.

I can't find 2" x 2" x 14g (0.083") angle listed anywhere as an available size, so I'm guessing that yours are really 2" x 2" x 1/8" (0.120").

So let's use this as another worked example (you need to measure the L1 dimensions and correct the first two parts):

1) Vertical strength of single tongue.
Vertical capacity (from web page table) = 20600 lb-in
Length L1 = 18 in (to be checked)
Max trailer weight = 20600 / 18 / 0.5 = 2290 lb

2) Horizontal strength of single tongue.
Horizontal capacity (from web page table) = 16500 lb-in
Length L1 = 18 in (to be checked)
Max trailer weight = 16500 / 18 / 0.5 = 1830 lb

3) Vertical strength of complete tongue
Vertical capacity of single tongue = 20600 lb-in
Vertical capacity of each angled brace = 3400 lb-in
Vertical capacity of complete tongue = 20600 + 3400 + 3400 = 27400 lb-in
Length L2 = 51 (tube) + 2 (coupler) = 53 in
Max trailer weight = 27400 / 53 / 0.5 = 1030 lb

The last max weight, 1030 lb, is the lowest, so that's the maximum trailer weight that passes the Aussie rule.

Paul will have to eat his 'Mack' comment - because those tubes are pretty thin, the total strength isn't that high.

So I'd say you have a sturdy, but not overbuilt, trailer chassis.

Andrew

[asianflava]

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.

Bitumen....I had to look it up. I've heard of Bituminous materials but didn't make the connection to asphalt.

[surveytech]

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

Anyone have the sizes?

I agree.

Though I would say I've been asking here for that info for about a year..... :cry:

Andrew

I know you have andrew.
It would be good to get all the specs on those two trailers and post them somewhere for future builders.

Anyone have a new trailer that they can measure?

Walter

[kirtsjc]

Thanks, Aussies!

Andrew

Thanks for keeping up on this topic - However, I noticed The Downunders forgot to mention "Daves" in their calculation! This will not doo!


Seriously, great work!

[kirtsjc]

Anyone have a new trailer that they can measure?

Walter

OOOO!!!!! I do, I do, me me me!


Will post and PM it by Sunday!

[angib]

(I'm slightly embarassed - this is becoming like my personal blog page, not a public thread!)

Cary,

I agree with pretty much all of what you've said.

On the web page I've shown the longitudinal strength of the sections and two 2" x 2" x 1/8" angles do indeed have a strength around 10,000 lb - this is in compression (ie, when braking, or crashing!) - in tension their strength is more like 27,000lb.

I'm presuming the part where you said "....would have 125lb tongue weight. So, it would only need to take about 250lb....." means you think the maximum acceleration of the hitch is around 2g. This is what the Aussie rules provide for, if the trailer has a 25% hitch weight - which is good, as I think quite a few of the teardrops shown on this forum have this sort of hitch weight percentage.

I presume you use 3/16" thick angle on the Camp-Inn as 1/8" angle only achieves about a 1.5g rating on a 125lb hitch weight.

The one item I don't agree on is the "built-in flex" argument - when I was a structural engineer, I heard that theory almost weekly and it is wrong in the vast majority of cases - even when accompanied by the "trees don't fall down because they can flex" analogy, that many people consider is 'proof' of its truth!

Andrew

[angib]

Andrew, You and the Aussie's forgot one

Yes, but......

Interestingly the Aussies require a horizontal strength of the drawbar/tongue that's the same as the vertical strength. That does seem excessive to me, but maybe they've got a reason for it.

So that reinforcement under Dean's tongue does pretty much nothing for the horizontal strength and that looks to me like a 2" (wide) x 3" (high) tongue, so it would have failed the horizontal test before the vertical test before it was stiffened.

Incidentally, if that's a 2" x 1/8" strap positioned 3" under a 2" x 3" x 11g tube (measured by Mark 1 eyeball), it increases the vertical strength by about 70% - if it's a 2" x 1/4" strap and it's 3" down, it triples the tube's vertical strength.

Andrew

[PaulC]

Andrew, I humbly accept being corrected re the Mack
Asian, I racked my brain trying to remember what you guys called it.
Kirt, I don't think the powers that be will ever let me convert them to daves
Cheers Gentlemen
Paul

[sdtripper2]

Hello, Andrew, Surveytech and All:

Harbor Freight Trailer INFO

If I understand the question right You want to know the tounge length for these two models of Harbor freight trailers.

40597 HF-Trailer
Main selection page = http://tinyurl.com/jmkzd
Manual
http://www.harborfreight.com/manuals/40 ... /40597.PDF

See specs page (2)
Overall length = 138.22"
Bed length = 96.00"
Tounge length = 42.25"

************************

90154 HF-Trailer
Main selection page = http://tinyurl.com/7hq7z
Manual
http://www.harborfreight.com/manuals/90 ... /90154.pdf

See specs page (2)
Overall length = 140.00"
Bed length = 96.00"
Tounge length = 44.00"

[Chris C]

My trailer tongue is 2x3x14ga and the A-frame is 2" anglex14ga. Right now the tongue is 51".....but that is without coupler.

Sheesh - in every group, there is always one........

OK, I've now modified the charts to include 14g tubes, but you'll need to go to the web page to see all the possible sections. Your frame design is a perfect example of what I've called a 'composite tongue', so the strength has to be checked in three places.

I would add 2" to the bare tube lengths to get the approximate length to the centre of the hitch ball.

I can't find 2" x 2" x 14g (0.083") angle listed anywhere as an available size, so I'm guessing that yours are really 2" x 2" x 1/8" (0.120").

So let's use this as another worked example (you need to measure the L1 dimensions and correct the first two parts):

1) Vertical strength of single tongue.
Vertical capacity (from web page table) = 20600 lb-in
Length L1 = 18 in (to be checked)
Max trailer weight = 20600 / 18 / 0.5 = 2290 lb

2) Horizontal strength of single tongue.
Horizontal capacity (from web page table) = 16500 lb-in
Length L1 = 18 in (to be checked)
Max trailer weight = 16500 / 18 / 0.5 = 1830 lb

3) Vertical strength of complete tongue
Vertical capacity of single tongue = 20600 lb-in
Vertical capacity of each angled brace = 3400 lb-in
Vertical capacity of complete tongue = 20600 + 3400 + 3400 = 27400 lb-in
Length L2 = 51 (tube) + 2 (coupler) = 53 in
Max trailer weight = 27400 / 53 / 0.5 = 1030 lb

The last max weight, 1030 lb, is the lowest, so that's the maximum trailer weight that passes the Aussie rule.

Paul will have to eat his 'Mack' comment - because those tubes are pretty thin, the total strength isn't that high.

So I'd say you have a sturdy, but not overbuilt, trailer chassis.

Andrew

Sorry to have been the "there's always one" ! But thanks for walking me through it. I couldn't figure out how to get there. Your last sentence is exactly what I like to hear and exactly what I was trying to build. Thanks for taking the time, Andrew.

[surveytech]

Steve,
that is a good start!
Specs for the 1800 lb harbor freight trailer.....
48-1/2 by 96" bed
2"coupler
frame is 11 gauge steel
overall length 138-1/4"
overall width 66-1/8"
"do not use this product if under the influence of drugs or alcohol" (bummer)
"do not exceed 45 mph when towing this trailer"

still need.........
dimensions of the trailer frame steel.
dimensions of the tongue steel.
location of the axle from front cross member
location of all cross members
deck height
trailer weight
and who know what else.....

Specs on the 1450lb harbor freight trailer...

bed dimensions 4 x 8
coupler size 1-7/8"
overall dimensions 140" x 61-1/2 wide x 19- 1/4" high
trailer weight 266 lbs.

still need.......
most of the stuff listed above.

Hey this is a start though!
thanks .

Walter

[Cary Winch]

Andrew,

Hey nice catch on the tensile vs compressive flip flop, I was only doing that in my head. We do use 1/8" angle on our frames. Keep in mind they are only 3 footers. On our longer 560 series we add more structure accordingly.

The flexible member is in the body, not the frame. I too am not big on the idea of flexing the frame. It works as a shock absorber to reduce the shock load to the frame.

I do still need to point out that people need to realize that the load this chart calculates is the weight at the joint of the tongue to the rest of the frame not the total weight of the trailer. I think this is still being misunderstood here in the case of a teardrop application. My example I was using was showing how it is correct for this case. To further show what I mean figure that someone where to strap 500lb of lead weight on top of the axle. Then assume that the tongue weight was not increasing accordingly for safe towing. This would have no affect on these calculations. This is an example of why I say this chart does not correctly give you the max weights on a fixed weight location trailer like a teardrop.

Cary