When RV’ers are considering a fyfde tsjil 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.

Hege kwaliteit JSK casting fyfde tsjil 37C

It swiertepunt fan in fyfde tsjil is heul heech, it sydmuorregebiet om dwerswyn te fangen is massaal, de measte ienheden hawwe basisophingingen foar leafspring, wylst mar in pear skokbrekers hawwe. De fyfde tsjil hitch is net yngewikkeld. It bestiet út in ienfâldige pivot punt dat is likernôch fjouwer fuotten boppe de grûn, sittend oer in basis live axle truck suspension.

Swivel pin doazen tastean in yndrukwekkende turn radius fan 90 graden, mar wat stabiliteit op snelwei snelheden is ferlern.

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.

Swivel pin doazen yn prinsipe biedt brûkers fan fyfde tsjillen deselde draaiende skaaimerken fan in reis trailer. Mar as jo te skerp draaie, sil it fyfde tsjil yn 'e kabine fan' e frachtwein rinne, wêrtroch skea oan beide auto's feroarsaket.

De Pull Rite automatyske sliding hitch.

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.

Troch se yn swiere wyn op deselde frachtwein efterinoar te slepen en se troch deselde handlingskursus te rinnen, koe ik gjin ferskil yn ôfhanneling fernimme. Yn teory soe der wêze moatten. Ik tink dat de ôfhanneling beheinings oplein troch it swiertepunt komme yn toanielstik lang foar it ferskil yn de pin gewicht.

Doe't fyfde tsjillen waarden yntrodusearre op 'e merk, alle frachtweinen hie acht-foet doazen mei de efterste axle being 54 inches út de efterkant fan' e cab. Dit tastien de acht-foet breed fyfde tsjil te meitsje in bocht 90 graden oan de frachtwein foar manoeuvre. Tsjintwurdich hawwe de measte frachtweinen in doaze fan fiif foet, seis inch of seis foet, seis inch mei de as 30 oant 40 inch efter de cab. As jo ​​​​dus te skerp draaie, rint it fiifde tsjil yn 'e kabine fan 'e frachtwein, wêrtroch't skea oan beide weinen ûntstiet.

De earste oplossing foar dit probleem wie de ynfiering fan sliding hitches, dy't mei de hân slide de pin posysje efter de efterste axle te tastean foar strakkere manoeuvre op lege snelheden. Dizze bewiisden effektyf en wurde noch altyd faak brûkt. It foardiel is dat in koarte doaze mei in slide hitch is dramatysk mear manoeuvreerber as in lange doaze. Ik kin parkeare in 35-foot fiifde tsjil trailer yn in strakke camping mei in koarte doaze in stik makliker as mei in 28-foot fiifde tsjil mei in lange doaze.

Sa'n 15 jier lyn pionierde Pull Rite de automatyske schuifhaak en Demco makket no ek ien. Dizze hitches behannelje as in konvinsjonele fyfde tsjil hitch op snelwei snelheid, mar automatysk slide efterút om te tastean makliker manoeuvre. De ûnderkant is dat se $ 800 oant $ 1.500 djoerder binne as in fêste as manuele sliding fan ferlykbere kwaliteit. Dan wer hoege jo mar ien kear te ferjitten om in manuele slider te ferpleatsen en jo sille de ekstra kosten besparre hawwe.

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.

Koartlyn testen wy in draaiende pindoaze om te sjen hoefolle ferskil 20 inch oerhang echt makke. Wy rigged de pin doaze sadat wy koenen wikselje tusken in sliding hitch en in swiveling pin doaze op deselde trailer-truck kombinaasje.

Op ús testdei, dy't bestie út lichte wyn en in glêde dyk, wie it dreech om te sizzen oft de hitch draaide oer de as of 20 inch efter. Lykwols, doe't de dwerse wyn omheech skopte of as in frachtwein ús foarby kaam, koenen jo fiele hoe't de trailer de frachtwein rûn. It wie minder as ik ferwachte, mar it wie der wis.

By in ûntwykmanoeuvre, lykas in hommelse rydbaanwikseling, wiene wy ​​hielendal stabyl mei 0 persint oerhang. De trailer waard lykwols folle mear in hânfol mei 15 prosint oerhang.

By 0 prosint kaam de oanhingwein fuort nei in flugge rydbaanwikseling, mar mei de 15 prosint oerhing wiene der in pear ekstra swaaien fan side nei side. Myn soarch is dat dit ûntwerp fan hitch, kombinearre mei de lichtere pingewichten, kin resultearje yn in ynstabile situaasje.

D'r binne wat moaie funksjes mei de draaiende pindoaze. It is ienfâldiger dan in automatyske slider en makliker te ferbinen. Wês gewoan bewust dat jo miskien wat feiligens en stabiliteit hannelje om dy funksjes te krijen.