When RV’ers are considering a roda kelima trailer they often ask if it will feel more stable on the road than a travel trailer or a motorhome. Fifth wheels are very stable on a highway and are rarely affected by cross winds or passing trucks. But when you look at a fifth wheel’s design, it would be easy to wonder how they could be stable at all.

JSK tuangan roda kelima 37C berkualiti tinggi

Pusat graviti roda kelima adalah sangat tinggi, kawasan dinding sisi untuk menangkap angin silang adalah besar, kebanyakan unit mempunyai ampaian spring daun asas, manakala hanya sedikit yang mempunyai penyerap hentak. Hitch roda kelima tidak rumit. Ia terdiri daripada titik pangsi mudah yang kira-kira empat kaki di atas tanah, terletak di atas penggantungan trak gandar hidup asas.

Kotak pin pusing membolehkan jejari pusingan mengagumkan 90 darjah, tetapi beberapa kestabilan pada kelajuan lebuh raya hilang.

Compared with travel trailers, which can have a very low centre of gravity and a pivot point much closer to the ground (with weight distribution and sway controls), there is no contest between the two. When we do slalom and lane change tests, it’s obvious travel trailers handle much better. For example, a good handling travel trailer and tow vehicle can run through a 100-foot slalom close to 80 km/h. With a fifth wheel, the tires start leaving the road at 60 km/h. So, if I find myself in a situation where I need to manoeuver quickly to avoid an accident, I will take a properly set up travel trailer any time.

But fifth wheels do have their merits. Going straight down the highway on a windy day, it’s hard to match the driving ease of a fifth wheel in tow. This is due to one key advantage. Of all the measurements we conduct when assessing a tow vehicle for a trailer, a key element we have to consider is the amount of rear overhang. We look at the overhang as a percentage of the wheelbase. For instance, if the vehicle has a 100-inch wheelbase with 40 inches of rear overhang, the overhang is 40 percent of the wheel base (which would not be ideal). The best vehicles are around 30 percent.

But, with a fifth wheel, the overhang is 0 percent of the wheelbase. From a driving perspective, this trumps most other factors I previously mentioned about fifth wheels. Even when making an emergency manoeuver, it’s easy to drive up to the point where the fifth wheel’s centre of gravity becomes the issue. In the slalom, I have had the wheels of a fifth wheel come a couple of feet off the ground and it felt completely stable in the cab. The only thing that made me realize that the wheels were off the ground was a quick glance in the side-view mirror.

Historically, a factor that contributes greatly to the stability of a fifth wheel is the pin or hitch weight was always a higher percentage of the total trailer weight – usually 20 percent. On a travel trailer, it’s normally 10 to 15 percent. This allowed the fifth wheel to have a longer distance from the pivot point to the axles, which makes any trailer more stable. For example a transport trailer with tandem wheels almost at the back of the trailer carries close to 50 percent of its weight on the tractor.

Kotak pin pusing pada asasnya menawarkan pengguna roda kelima ciri pusingan yang sama bagi treler perjalanan. Tetapi jika anda membelok terlalu tajam, roda kelima akan melanggar teksi trak, menyebabkan kerosakan kepada kedua-dua kenderaan.

Halangan gelongsor automatik Pull Rite.

Today, many fifth wheels are geared to tow with a half-ton, which means the loaded for travel pin weight needs to be less than 1,500 to 1,700 pounds. On many of these fifth wheels, the pin weight is 12 to 14 percent rather than 20 percent. The first time we had one of these lighter pin weight fifth wheels, I was quite concerned about what effect it might have on stability. On the lot we had two 10,000 pound fifths of the same brand and size – the only difference between the two models were the interior layouts. One unit had 1,100 pounds of pin weight and the other had 1,780 pounds.

Menariknya kembali ke belakang dalam angin kencang pada trak yang sama dan menjalankannya melalui laluan pengendalian yang sama, saya tidak dapat melihat sebarang perbezaan dalam pengendalian. Secara teori, sepatutnya ada. Saya fikir had pengendalian yang dikenakan oleh pusat graviti berlaku lama sebelum perbezaan dalam berat pin.

Apabila roda kelima diperkenalkan di pasaran, semua trak mempunyai kotak lapan kaki dengan gandar belakang berada 54 inci dari bahagian belakang teksi. Ini membolehkan roda kelima selebar lapan kaki membuat pusingan 90 darjah ke trak untuk bergerak. Hari ini, kebanyakan trak mempunyai kotak lima kaki, enam inci atau enam kaki, enam inci dengan gandar berada 30 hingga 40 inci di belakang teksi. Oleh itu, jika anda membelok terlalu tajam, roda kelima akan melanggar teksi trak, menyebabkan kerosakan kepada kedua-dua kenderaan.

Penyelesaian pertama untuk masalah ini ialah pengenalan gelongsor, yang secara manual meluncurkan kedudukan pin di belakang gandar belakang untuk membolehkan pergerakan yang lebih ketat pada kelajuan rendah. Ini terbukti berkesan dan masih sering digunakan. Faedahnya ialah kotak pendek dengan halangan gelongsor secara dramatik lebih mudah dikendalikan daripada kotak panjang. Saya boleh meletakkan treler roda kelima 35 kaki di tapak perkhemahan yang ketat dengan kotak pendek dengan lebih mudah berbanding dengan roda kelima 28 kaki dengan kotak panjang.

Kira-kira 15 tahun yang lalu Pull Rite mempelopori halangan gelongsor automatik dan Demco kini membuat satu juga. Hitch ini mengendalikan seperti halangan roda kelima konvensional pada kelajuan lebuh raya, tetapi secara automatik meluncur ke belakang untuk membolehkan pergerakan lebih mudah. Sisi buruknya ialah $800 hingga $1,500 lebih mahal daripada halangan gelongsor tetap atau manual dengan kualiti yang sama. Kemudian sekali lagi anda hanya perlu lupa untuk menggerakkan peluncur manual sekali dan anda akan menjimatkan kos tambahan.

A few years ago a swivelling pin box was introduced on the market, which features a fixed hitch situated over the axle. The pin box doesn’t pivot in the hitch, but rather is locked into the truck portion. A 20-inch bearing is built into the pin box located behind the axle where the trailer turns. While it allows an impressive 90-degree turn with the truck, some stability on the highway is lost. Though the pin weight of the fifth wheel is still placed directly over the axle the side to side pivot point is 20” behind the axle or to put it another way your truck now has a rear overhang equal to 15% of the wheelbase. Ultimately you wind up with the disadvantages of a fifth wheel and disadvantages of a travel trailers without the benefit of weight distribution or sway control.

When the swivelling pin box was introduced on the market, I asked the developer what kind of testing was done to determine how much stability is lost. The developer said there wasn’t any loss. I said there had to be and the conversation went downhill from there. It never concerned me a great deal as the product was rarely seen. But now I am seeing some manufacturers offering it as an option and doubt they understand how handling is affected with a swivelling pin box.

Baru-baru ini, kami telah menguji kotak pin berpusing untuk melihat berapa banyak perbezaan 20 inci terjual yang benar-benar dibuat. Kami memasang kotak pin supaya kami boleh bertukar antara halangan gelongsor dan kotak pin berpusing pada gabungan trak-treler yang sama.

Pada hari ujian kami, yang terdiri daripada angin kencang dan jalan yang lancar, adalah sukar untuk mengetahui sama ada halangan itu berputar di atas gandar atau 20 inci di belakang. Walau bagaimanapun, apabila angin lintang bertiup atau apabila trak melewati kami, anda dapat merasakan treler itu menolak trak itu. Ia kurang daripada yang saya jangkakan, tetapi ia pasti ada.

Semasa pergerakan mengelak, seperti pertukaran lorong secara tiba-tiba, kami benar-benar stabil dengan 0 peratus tidak terjual. Walau bagaimanapun, treler itu menjadi lebih segelintir dengan 15 peratus tidak terjual.

Pada 0 peratus, treler itu terus diluruskan selepas pertukaran lorong pantas, tetapi dengan 15 peratus tidak terjual terdapat beberapa ayunan tambahan dari sisi ke sisi. Kebimbangan saya ialah reka bentuk halangan ini, digabungkan dengan pemberat pin yang lebih ringan, boleh mengakibatkan keadaan tidak stabil.

Terdapat beberapa ciri bagus dengan kotak pin berputar. Ia lebih mudah daripada peluncur automatik dan lebih mudah untuk disambungkan. Hanya sedar bahawa anda mungkin menukar beberapa keselamatan dan kestabilan untuk mendapatkan ciri tersebut.