When RV’ers are considering a cúigiú roth 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.

An cúigiú roth réitigh JSK ardchaighdeáin 37C

Tá meáchanlár an chúigiú roth an-ard, tá limistéar an bhalla taobh chun trasghaoth a ghabháil ollmhór, tá fionraí earraigh duille bhunúsach ag an gcuid is mó de na haonaid, agus níl ionsúire turrainge ach ag cúpla. Níl an hitch cúigiú roth casta. Is éard atá ann pointe maighdeog simplí atá thart ar cheithre troigh os cionn na talún, ina shuí thar fionraí trucail acastóra beo bunúsach.

Ceadaíonn boscaí bioráin sclóine ga mórthaibhseach de 90 céim, ach cailltear roinnt cobhsaíochta ag luasanna an mhórbhealaigh.

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.

Tugann boscaí bioráin sclóine go bunúsach na tréithe casadh céanna atá ag leantóir taistil d'úsáideoirí cúigiú roth. Ach má chasann tú ró-ghéar, rachaidh an cúigiú roth isteach i gcábán na trucaile, rud a dhéanfaidh damáiste don dá fheithicil.

An hitch sleamhnáin uathoibríoch 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.

Agus iad á dtarraingt siar le cúl le gaotha troma ar an trucail chéanna agus á rith tríd an gcúrsa láimhseála céanna, ní raibh mé in ann aon difríocht sa láimhseáil a bhrath. Go teoiriciúil, ba chóir go raibh. Sílim go bhfuil na teorainneacha láimhseála a fhorchuirtear le lár an domhantarraingthe i bhfeidhm i bhfad roimh an difríocht i meáchan an bhioráin.

Nuair a tugadh an cúigiú roth isteach ar an margadh, bhí boscaí ocht gcos ag gach trucail agus bhí an t-acastóir cúil 54 orlach ó chúl an chábáin. Lig sé seo don chúigiú roth ocht dtroithe ar leithead cas 90 céim a dhéanamh chuig an trucail le haghaidh ainlithe. Sa lá atá inniu ann, tá bosca cúig throigh, sé orlach nó sé-troigh, sé orlach ag an gcuid is mó de na trucailí agus tá an t-acastóir 30 go 40 orlach taobh thiar den chábán. Mar sin, má iompaíonn tú ró-ghéar, rithfidh an cúigiú roth isteach i gcábán na trucaile, rud a dhéanfaidh damáiste don dá fheithicil.

Ba é an chéad réiteach ar an bhfadhb seo ná bacanna sleamhnáin a thabhairt isteach, a shleamhnaíonn de láimh an suíomh bioráin taobh thiar den acastóir cúil chun ainliú níos déine ar luas íseal a cheadú. Bhí siad seo éifeachtach agus fós úsáidtear iad go minic. Is é an buntáiste atá leis ná go bhfuil bosca gearr le hitch sleamhnáin i bhfad níos so-aistrithe ná bosca fada. Is féidir liom leantóir cúigiú roth 35 troigh a pháirceáil i láthair campála daingean le bosca gearr i bhfad níos éasca ná le cúigiú roth 28 troigh le bosca fada.

Thart ar 15 bliana ó shin bhí Pull Rite i gceannas ar an mbailiúchán uathoibríoch sleamhnáin agus déanann Demco ceann freisin. Láimhseálann na hitches seo cosúil le hitch cúigiú roth traidisiúnta ar luas an mhórbhealaigh, ach sleamhnaíonn siar go huathoibríoch chun ainliú níos éasca a éascú. Is é an taobh thíos go bhfuil siad $800 go $1,500 níos daoire ná hitch sleamhnáin seasta nó láimhe den chaighdeán céanna. Ansin arís ní gá duit dearmad a dhéanamh ach sleamhnán láimhe a bhogadh uair amháin agus beidh an costas breise sábháilte agat.

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.

Le déanaí, rinneamar tástáil ar bhosca bioráin sclóine chun a fháil amach cé mhéad difríochta a rinne 20 orlach de overhang i ndáiríre. Rinneamar an bosca bioráin a rigeáil ionas go bhféadfaimis aistriú idir hitch sleamhnáin agus bosca bioráin sclóine ar an meascán leantóir-trucail chéanna.

Ar ár lá tástála, a bhí comhdhéanta de ghaotha éadroma agus bóthar mín, bhí sé deacair a rá an raibh an hitch ag pivotáil thar an acastóir nó 20 orlach taobh thiar de. Mar sin féin, nuair a tháinig na crosghaoithe suas nó nuair a chuaigh trucail thar fúinn, d’fhéadfá an leantóir a mhothú ag brú na trucaile timpeall. Bhí sé níos lú ná mar a bhí súil agam, ach is cinnte go raibh sé ann.

Le linn ainlithe imghabhála, cosúil le hathrú tobann lána, bhíomar iomlán cobhsaí agus 0 faoin gcéad ar crochadh. Mar sin féin, tháinig an leantóir i bhfad níos mó de dornán le 15 faoin gcéad overhang.

Ag 0 faoin gcéad, chuaigh an leantóir díreach amach díreach tar éis athrú lána tapa, ach leis an 15 faoin gcéad overhang bhí cúpla luascáin breise ó thaobh go taobh. Is é an t-imní atá orm ná go bhféadfadh cás éagobhsaí a bheith mar thoradh ar dhearadh na hitch seo, in éineacht leis na meáchain bioráin níos éadroime.

Tá roinnt gnéithe deas leis an mbosca bioráin pivoting. Tá sé níos simplí ná sleamhnán uathoibríoch agus níos éasca le nascadh. Tabhair faoi deara go mb'fhéidir go bhfuil tú ag trádáil as roinnt sábháilteachta agus cobhsaíochta chun na gnéithe sin a fháil.