Jacking Points, Plates

[machighlander]

hi, tomorrow i am changing my offside wheel as i noticed some unwelcome cracks and small splits on the tyrewall.

i have a trolley jack in the garage which i intend to use, but i had a look underneath the caravan to look for jacking points.

the handbook gives reference to the original alko scissor type and shows the brackets, however, it doesen't say where to place the trolley jack.

i take it that it would go under the plates which are visible near the back of the wheel drum on the outer end of the axle ?

it states clearly in the handbook never to jack up using the chassis, these plates look as if they are attached.

cheers.

 

[Sproket]

As you have already read .... " all jacking must be done on the axle or the axle plate, anywhere else on the chassis may damage the chassis."

Ideally couple the van up to the car before you change the wheel

For further reading see below ....

AL-KO caravan/chassis

al-ko caravan/chassis

AL-KOmatic

al-komatic

 

[Damian]

The reinforced web just behind the drum is fine to use as a jacking point, or the axle tube as close to the drum as possible

 

[Guest]

The jacking plates that you see advertised by Alko and others do make me wonder a bit.

On the one hand you are told never to use the chassis for jacking and then on the other hand if you bolt these plates to the chassis then you can jack it.

One does wonder if you were to bolt the plates as advised, could you then use that as a jacking point for a trolley jack? It would certainly save crawling undre neath to get right under the axle chassis join.

 

[machighlander]

job done folks, cheers for the advice, no probs.

scotch lad, you have said exactly what i was thinking regarding these plates, i looked underneath and seen there was plates attached to the chassis just behind the wheel hub and i reckoned this was the point to use the jack. i used my trolley jack with a packer of wood and then proceeded to do the job.

it did strike me though that these plates were attached to the chassis, so therefore the strain must have been going through it as well. i didnt have any problems and job was done in no time, but i would like some clarification if its alright to use these said plates.

cheers.

 

[Sproket]

That's what they are designed for, but i find this the easier option.

 

[xtrailman]

I have been jacking my vans up since 1992, as described by damian above, i prefer the reinforced plate to the tube.

That is until this afternoon, today i have fitted the carajack brackets, i cant recommended these brackets, the way they are designed means there is a small gap between the rear of the plate and the chassis, the bottom bolt actually distorts the chassis, not a lot i you can see it, looking at sprockets photo, to me they look like the back of the hole rests onto the chassis, is that correct?

But anyway, as i have said today i've fitted the brackets, jacked up the van, used the jack and i am quite happy with it, replaced both wheels and while i was at it tried my old bottle jack on the new bracket works ok, so using both jacks ive had the wheels of the deck and set up the brakes.

I have to say its a lot easier than jacking with the trolley jack onto the reinforced plate, the only thing i would do differently is buy the kojacklite, unless of cause the plates are the same design as the carjack.

 

[machighlander]

sproket, i dont get this. the bracket you show is attached directly to the chassis member, therefore when using the jack surely the strain is put onto this as well.

i would have thought that the axle or plates fitted on outer of it behind the hub would cause less strain.

so whats the difference using that attachment than just jacking up below the same part of the chassis ?

 

[Guest]

exactement mon ami.

 

[machighlander]

exactement mon ami.

gid yin.

 

[antrimboy]

I think the reason is because the chassis is L shaped, and jacking up directly underneath the horizontal part could cause it to buckle - just my own thoughts!!

 

[Sproket]

As per AL-KO web site..... al-ko caravan/chassis

AL-KO chassis from 1992 onwards

have 2 holes punched in the chassis

members, each side (rear of the

axle); to accept the brackets for the

Jack(s). (See Accessory Price List).

Corner Steadies may be used for

stability ONLY, when the caravan is

in the jacked position.

The caravan should never be lifted

by jacking up under the chassis

member.......

 

[Sproket]

I think the reason is because the chassis is L shaped, and jacking up directly underneath the horizontal part could cause it to buckle - just my own thoughts!!

That's correct....

 

[xtrailman]

If you jack it up on the chassis bottom, as that so called approved caravan engineer did to my caravan two yeas ago, then you will bend the bottom plate over, not to mention he used no interface between the trolley jack, so he also "bit" through the galvanising, he jacked it just below the holes, DON'T do it.

 

[machighlander]

sproket, was never misdoubting you buddy, only giving my thoughts on what we are told by manufacturers about not jacking up directly below chassis, then they have some pre drilled holes through it to accomodate a bracket ?

i can see the point with eddies' reply, will go for that for an explanation as to why

cheers eddie.

 

[Guest]

So, if I undertsand this correctly.

You cannot directly jack the chassis even if it is just behind the wheel, but you can jack the same point if a bracket has been bolted to the chassis member as long as the bottom of the bracket is lower than the bottom of the chassis edge.

You have to ask yourself why on earth the brackets were not included as an integral part of the chassis in the first place, and marked as 'jacking points'. Oh I forgot it is because ALKO want to sell you a highly expensive jacking assembly that is not very steady unless you are on hard flat ground, lower the steady legs and keep the car attached.

 

[Sproket]

So, if I undertsand this correctly.

You cannot directly jack the chassis even if it is just behind the wheel, but you can jack the same point if a bracket has been bolted to the chassis member as long as the bottom of the bracket is lower than the bottom of the chassis edge.

You have to ask yourself why on earth the brackets were not included as an integral part of the chassis in the first place, and marked as 'jacking points'. Oh I forgot it is because ALKO want to sell you a highly expensive jacking assembly that is not very steady unless you are on hard flat ground, lower the steady legs and keep the car attached.

Is that clever marketing ? ..... it's a bit like dangling the carrot.... what else can we sell them....?

 

[xtrailman]

scotch lad

no you are not understanding correctly, read damien's post above.

trust me if you jack below the holes used for the alko jack, onto the bottom lip you can bend the bottom lip, it's not strong enough, where as behind the wheel its double plated.

 

[Sproket]

Ray

"" looking at sprockets photo, to me they look like the back of the hole rests onto the chassis, is that correct? ""

Yes it rest against the chassis and is clamped up tight.

 

[xtrailman]

Thanks sprocket, if i had known before hand i would have paid the extra for the kojacklite, but that's the problem buying sight unseen, apart from a picture, i have not seen either one, just took the recommendation from someone on another thread.

A very poor design, the jack is fine, i refer to the mounting brackets, i will have to look at taking them off and packing in-between the back of the plate and chassis, but the offside was a pig to get to the bolts.

 

[WatsonJohnG]

The reason they are supplied as an extra is

 

[Reg]

It's all quite simple...... if you understand Applied Mechanics!

If you place the jack under the chassis lower flange you are applying a bending force onto the flange which is approx 2mm thick (a guess!). This would act as lever or bending moment at the point where the horizontal flange joins the vertical flange (critical point) and so bend the lower flange. If you really want to know the stress at the critical point = Load(W) x length of flange(l) divided by the section modulus(Z)!

By placing a bracket onto the side of the chassis the load is now transferred to the vertical member of the chassis and as the vertical flange is approx 150mm (another guess) but still only 2mm thick the section modulus(Z) now becomes approx. 75 times greater than the lower flange. the only bending moment takes place on the bracket which you will note is made up of "U" shaped sections cleverly designed to withstand the load.

So you can apply (approx) a 75 times greater load onto the vertical side of the chassis than you can onto the lower flange!

And that's putting it in it's simplest terms!

One has to ask why don't they add jacking points to the chassis similar to the jacking points on a car?

"AND SO ENDETH TODAYS LESSON"

 

[WatsonJohnG]

It's all quite simple...... if you understand Applied Mechanics!

If you place the jack under the chassis lower flange you are applying a bending force onto the flange which is approx 2mm thick (a guess!). This would act as lever or bending moment at the point where the horizontal flange joins the vertical flange (critical point) and so bend the lower flange. If you really want to know the stress at the critical point = Load(W) x length of flange(l) divided by the section modulus(Z)!

By placing a bracket onto the side of the chassis the load is now transferred to the vertical member of the chassis and as the vertical flange is approx 150mm (another guess) but still only 2mm thick the section modulus(Z) now becomes approx. 75 times greater than the lower flange. the only bending moment takes place on the bracket which you will note is made up of "U" shaped sections cleverly designed to withstand the load.

So you can apply (approx) a 75 times greater load onto the vertical side of the chassis than you can onto the lower flange!

And that's putting it in it's simplest terms!

One has to ask why don't they add jacking points to the chassis similar to the jacking points on a car?

"AND SO ENDETH TODAYS LESSON"

AMEN

 

[Guest]

I fully understand why one should not jack a piece of basically angle iron as it will certainly buckle and also if you add a rigid plate then the weight is adsorbed by the vertical, but as I and others have stated, why the H..l were these plates not included as standard and clearly marked as jacking points. Again, I come to the conclusion that this was designed to create commercial advantages by selling expensive after market add -ons.