Stepframe Semi trailer chassis

[jd6820]

Alreet folks,

Just looking at my ARB trailer that needs a bit of love and attention. Been looking at the chassis and noticed the crossmembers are slid through slots in the central chassis beams. Any reason for this vs welded to the side of the beams? Cause I’ve a few to replace and sliding them through isn’t possible unless I de-constructed the whole trailer. I was thinking it had something to do with allowing the trailer to flex without cracking too many welds or at least increasing the time before they do crack?

Be interested to hear your thoughts…

 

[DaveDCB]

One for @Mogman ?

 

[V8Druid]

most are made that way for, as you say, flexibility and resilience ... welded onto the flanges'd break off pretty quickly
if you wanted to slide some new ones through, split them in the centre and join in situ with a re-enforcing plate

 

[jd6820]

most are made that way for, as you say, flexibility and resilience ... welded onto the flanges'd break off pretty quickly
if you wanted to slide some new ones through, split them in the centre and join in situ with a re-enforcing plate

Been tapping away and corrosion is worse than expected… Looks like the central UB are not great yet rest of chassis is good. Would best way be split the chassis to replace all crossmembers and middle beams? I know you are well versed in fabrication and techniques.

 

[V8Druid]

Been tapping away and corrosion is worse than expected… Looks like the central UB are not great yet rest of chassis is good. Would best way be split the chassis to replace all crossmembers and middle beams? I know you are well versed in fabrication and techniques.

some pix'd help understand clearer, but the two main spines are the chassis -- everything else is 'hung' off them

 

[jd6820]

some pix'd help understand clearer, but the two main spines are the chassis -- everything else is 'hung' off them

The blue arrow marks the rotten ub that is essentially the chassis. The green line represents the members that could also do with replacing. The crossmembers are slotted through cutouts in the chassis and fixed with one weld down the web of the crossmembers.

The red arow is the outer ub which are bigger than the chassis ub would need to be removed to install new crossmembers the full width of the trailer as one piece items?

 

[jd6820]

More pictures showing trailer as a whole…

 

[V8Druid]

massive can of worms JD ... A LOT of work

 

[TiltyShaun]

View attachment 66847

The blue arrow marks the rotten ub that is essentially the chassis. The green line represents the members that could also do with replacing. The crossmembers are slotted through cutouts in the chassis and fixed with one weld down the web of the crossmembers.

The red arow is the outer ub which are bigger than the chassis ub would need to be removed to install new crossmembers the full width of the trailer as one piece items?

Why does the green beam need replacing?

 

[Mogman]

Looks like a fair job
Did mine a couple of years back took the rotten cross members out and slid palased fence posts in
(just the right size) had to cut them into three to get them in
Had one main cross beam with rot in the web so cut the shite out and plated it up an ground the welds flat a coat of stone chip paint and all good for the MOT
Oh and I didn’t take the floor off just rolled the trailer on its side

But I’m after some keuin (hard wood flooring) if you know of a good supplier

 

[V8Druid]

Looks like a fair job
Did mine a couple of years back took the rotten cross members out and slid palased fence posts in
(just the right size) had to cut them into three to get them in
Had one main cross beam with rot in the web so cut the shite out and plated it up an ground the welds flat a coat of stone chip paint and all good for the MOT
Oh and I didn’t take the floor off just rolled the trailer on its side
View attachment 66852
But I’m after some keuin (hard wood flooring) if you know of a good supplier

have bought Keruing half lap for beds from a merchants in Gloucester a few times - specialised in hardwoods - sadly I can't recall their name and paperwork is long gone (up in smoke) .. a search for 'Keruing half lap boards' ought to produce results though Mog

 

[jd6820]

Why does the green beam need replacing?

That particular one doesn’t but the chassis has holes under each member pretty much all the way along so if changing the chassis may as well do the members too. I just can’t see an easy way of dropping the middle out and replacing it. Steel would cost £3500, trailer was scrap price but more solid than a lot of lowloaders I’ve been to look at anything sub £15k seems to have similar rot that has been patched or covered to get through an MOT. I’m wondering whether to scrap or keep and fix at this stage…

 

[jd6820]

Looks like a fair job
Did mine a couple of years back took the rotten cross members out and slid palased fence posts in
(just the right size) had to cut them into three to get them in
Had one main cross beam with rot in the web so cut the shite out and plated it up an ground the welds flat a coat of stone chip paint and all good for the MOT
Oh and I didn’t take the floor off just rolled the trailer on its side
View attachment 66852
But I’m after some keuin (hard wood flooring) if you know of a good supplier

When you split them into three how did you weld them back in place. We were gonna do the same but a local fabricator said we’d cause cracking in the weld if we fully welded the members into position.

Priced up online and calculated to do a trailer in 35mm boards would be about £4000!

 

[jd6820]

massive can of worms JD ... A LOT of work

Yeah just deciding whether to bother or not. Thing is £15k doesn’t get you a like new trailer and we’ve costed repairs excluding time at way less than this including full shotblast and paint. Would last us out hopefully then. Axles are good, recent new brake chamber and some bags so it’s do we bother? I was gonna lay old middle section on ground and build new section identical on top then weld back into chassis. Till someone suggested the welded members would allow less flex that ones slid through chassis and only welded down one side of the web on each member. I can weld just not always sure on the methodology behind weld placement. I thought the chassis was cut out to speed assembly and reduce error rather than for flex reasons?

 

[V8Druid]

Yeah just deciding whether to bother or not. Thing is £15k doesn’t get you a like new trailer and we’ve costed repairs excluding time at way less than this including full shotblast and paint. Would last us out hopefully then. Axles are good, recent new brake chamber and some bags so it’s do we bother? I was gonna lay old middle section on ground and build new section identical on top then weld back into chassis. Till someone suggested the welded members would allow less flex that ones slid through chassis and only welded down one side of the web on each member. I can weld just not always sure on the methodology behind weld placement. I thought the chassis was cut out to speed assembly and reduce error rather than for flex reasons?

dilemma for sure
IF I was gonna tackle it .....
I'd flip that over onto some trestles/sleeper beds and build a new centre chassis, upside down, on trestles along side (obviously on a good flat surface) ... get the new cross members all placed/installed, transfer all the running gear and ancillaries over to the new chassis and then finally lop off the outer side members, clean (repair as needed) and attach to the new assembly ... as said a LOT of work - do-able, but at significant cost - but again as you say, finding a decent s/h replacement'd be like finding unicorn poo.

 

[kato512]

Snowball engineering has a 3 part series on YouTube although it's an agri low loader it will give you some ideas.

 

[pettsy]

I’m no fabricator, but by the time you’ve put all the time and money into that, you might have a structurally sound trailer but it’s still an old-ish trailer that’s done the best days of its work. On the other hand I don’t know how much you use it, maybe say £10k done and on the road makes it a cheap lowloader that only goes out once a week locally

 

[6feetdown]

have bought Keruing half lap for beds from a merchants in Gloucester a few times - specialised in hardwoods - sadly I can't recall their name and paperwork is long gone (up in smoke) .. a search for 'Keruing half lap boards' ought to produce results though Mog

Did they have yellow wagons? Pretty sure we used them a cpl times also boys across the road

 

[V8Druid]

Did they have yellow wagons? Pretty sure we used them a cpl times also boys across the road

you may be right ... their name is on the tip of my tongue, just can't quite recall it though ... want to say Robins, but they were Bristol

 

[Mogman]

When you split them into three how did you weld them back in place. We were gonna do the same but a local fabricator said we’d cause cracking in the weld if we fully welded the members into position.

Priced up online and calculated to do a trailer in 35mm boards would be about £4000!

I welded them back together to make one piece
then welded to the outer ends to the side steels and where they pass through the main chassis just a vertical run up the web of the piece that I’d just welded together to the main chassis

Was a lot of work
but finding a trailer that the ramps fold down flat on the deck was an uphill battle plus I knew what it was like underneath to buy a second had one you are sometimes buying someone else’s problems

I’ve fitted 4 new discs 3 calipers full sets of pads and a couple of chambers so I’m in for the duration

But I did buy it in 2011 (that time has gone quick)
Oh and never failed an MOT