securing bull bar to chassi

[Wambat]

hey guys,

so last night, i was a little daft, and when reversing in the carpark at work, i was looking behinde me, thinking that the front end had plenty of room to swing past the i beam that supports the next level, but unfortunantly i didnt, and the i beam decided my car would do better without the bull bar i had attached to the front end!!!!! if i could up load or send photos off my phone to show you the carnage i would, but i cant.


so this is sort of a blessing in disguise, as i wanted to creat my own bull bar any way, being a fitter and turnere buy trade, and loving to weld i figured it would be a good thing to do. however, when i riped said bull bar off, it has distroyed all the captive nuts too, they are all poped of the chassi. and i wasnt going to use them any way when i did make one, so after all this useless rambling i come to my two questions(and possibly a couple sub questions)

first one is how do i best remove this from the drivers side chassi rail, it is in my way and there are two sheered bolts in the captive nuts that have to come out!!!!



i thought that a plasma cutter would be best as i am not getting an angle grinder in there and i am not using a die grinder, and an oxy would be a bit to messy and would require a fair bit of cleaning up after to be good enough to mount stuff too.

the second is about my ideas to clamp the bull bar onto my chassis

this is the passenger side, note how there are no more captive nuts except on the top lol.....



i am thinking of sandwiching the chassi rails like so



if i remnber from trade school correctly it is quite strong to bolt through and sandwhich a plate in the middle with two plates ithere side.

i want to make sure they are strong as i wish to have the plate protrude out for the sheet with am eylet for a d shackle to go through to use it as a recovery point, will this mounting be strong enough for this??? and for eventualy installing a winch??

if at this point your wondering what i drive its a 75, and on the front of the chassi there are only two bolts per side, so 8 in total, and that concerns me, i plan on the two outsides of the rails to drill another two holes further back, and possibly on the inside ones, use two holes just after it ends at the front (they are not even and the holes on the inside are to far back for me to have others) so if i go a little further forward i might be able to clamp it with an extra two bolts, if this works out, then i will have 16 bolds holding it on instead of 8, ( or in the case of my bar cause of the previous owner 6)

so is there any thing i need to know before starting this, or any advice people could lend.

oh i am thinking of using 10mm for the clamping plates, the outsides ones drilled through, the inside ones taped, with a nyloc welded onto the plate, and as far as i am aware high tensile bolts are the best to use for the bull bar?? but the last sets i had on it rusted a bit, and i dont want them to rust that far, so is stainless out of the questions, or should i go unbrakos??(socket head cap screws) of 12mm in size


cheers guys

Alistair

[Loanrangie]

Why not just drill out the old captive nuts and fit crush tubes .

[shakes]

Why not just drill out the old captive nuts and fit crush tubes .

x2 easily the best option.

[Wambat]

cause i want this strong, strong enough to hang my carr off, its jsut the way i like to do things.

also withought being there, and seeing the chassi in person or without you having seen a 75s before, ( i am assuming this from your answer) the holes dont line up, so i cant fit crush tubes, and there are no captive nuts left,


basicaly the options are, use plates, or weld on new captive nuts,

also, as i think more i am starting to remember more, witht he plates i have more surface incontact witht he chassi to help disspate energy over the surface area, with only a nut on the back it could try to just pull the nut out through the chassis, (one hole will deffinatly already have this problem as the chassi has had a bump before i got it, and when i was fitting the bar i had to give it a few hits but couldnt get it righ and had to grind it a little bit so it is thinner, so if i were to put a nut behinde that hole it will definantly pull through at a later stage, and i really dont want to have a bull bar hurtling trhough the air when i get recovered.

[shakes]

no I have not been directly been involved with 75's but sierra's, patrols and rangeys. also custom suspension links in 180b's for rally use and toyota sprinters for circuit sprints and hillclimbs, I've seen crush tubes with external plating work extremly well, survive much abuse and be relatively easy to install.

So I am sure the same concepts can be used. By plating both sides of the chassis and bolted I can see the chassis possibly being torn away from itself along the fold or central weld upon hard impact. But by the same token if your impacting the front end that hard I'm sure that how you suggested or how we suggested the mountings would be the least of your concerns.

I'm far from an engineer, and havent had huge amounts of experience so I'd like some of the more senior members to comment

[bazzle]

Drill out if you can.
Those 12mm bolts are more than enough to hang your 4wd off, even 1 of them would do that.
If you cant drill out use a chisel and the captive nuts will peel away from the chassis.
You can drill right thru like you want and run a crush tube ..

You wont get any strength from plates that will slide more than you think when hit.

Bazzle

[Loanrangie]

No i havent had anything to do with 75's, i dont work on ancient technology

[supazuk]

this is what i did to my sierra.

trimmed the chassis and slipped the plate over the chassis rail and tied it into the body mount.

then the bar mount bolts to the chassis plate.

[Loanrangie]

I hope there are more welds holding that plate on

[PBBIZ2]

When my 75 series was fitted with a Kaymar rear bar, they cold chiselled off the nuts - real easy, and replaced them with standard nuts. For the nuts further down the frame that were difficult ti reach, they welded a piece of 3mm steel wire to the hex face of the nut to allow the nut to be located. Worked very well, was stronger than the original as they ran a larger drill thru the holes and usd bigger bolts and nuts. There was no problem tightening them up either. Go this way and save some time and effort is my recommendation.

[Wambat]

shakes and loan rangie, you have miss interpreted what i said, i never said crush tubes wouldnt work, IF the holes are in line, but these holes are NOT inline, so if you think a long bolt through a crush tube and on say a 20 - 30 degree angle i will surely do that.......

no, i think having the bolts at 90 degrees is the only way to do it, so there for i cannot use crush tubes, i am sorry i did not mean to insinuate that you had no idea what you were talking about, mearly stating that if you have not seen the front end you would understand why crush tubes is not an option....


spazuk - them plates look really good, how ever, my body mounts are 100 mm out father than the chassi rails so i cant actually slide something over them unfortunatly, as i had throught of the same idea but like i said unfortunatly i cannot use that tecnique,


bazzle, the captive nuts are a sinch to get off, i needed one off i just used a spanner, twist pop,


also one thing no one has had any input on yet, is the right chassis rails, i need that block out before i can do any thing...


also from what i remember with trade school, if your using the two plates, and everything is torqued up correctly, there will be no slipping, also would you not assume that with the plates with more surrface area it would have more friction and there fore less chance of slipping??

also like i said, the holes are offset and i just dont think doing so with the bolt would be a very good idea, think fellas, if you have to snatch me out of a bog hole, would you not want to make sure my bar is tight enough that its not coming in through the read of your car!!!!

safety is what i am thinking off, and even though it sounds like i am being pig headed, i am willing to listen, spciffically when its agood idea, and if i have to i will go out get a long screw driver and pput it through the holes and take a photo so you can see the angles i am talking about.

[Wambat]

When my 75 series was fitted with a Kaymar rear bar, they cold chiselled off the nuts - real easy, and replaced them with standard nuts. For the nuts further down the frame that were difficult ti reach, they welded a piece of 3mm steel wire to the hex face of the nut to allow the nut to be located. Worked very well, was stronger than the original as they ran a larger drill thru the holes and usd bigger bolts and nuts. There was no problem tightening them up either. Go this way and save some time and effort is my recommendation.

mate that is a good idea, one that i have used too, it works well. but i have no need for it, as depending on how you design the bar, you would be able to get a spanner in the back,

also if i weld them to said plate, it dosent matter they are captive, and if fully welded they wont come off like the tacs on a captive nut will.


also i enjoy fabricating things, so putting the extra effort in is no worrys to me, i dont really care about saving time/

[PBBIZ2]

Alistair,

I think the big clamping plates on both sides will not give you a very good firm mounting. Reason being, you are spreading the clamping force across a wide area, so the location pressure will be much lower than if you used nuts on the inside and had the heavier mounting plate on the outside, that the bolt went thru. You may find the bullbar pivots downwards over time and without welding some sort of keeper plate to the chassis rail itself, its going to piss you off.

The other thing you might need to do to stop the pivoting is use very close tolerance on the drilled holes to bolt dia to reduce the movement, OR consider a top plate/bottom plate configuration, like a box section RHS, so the whole assy slides onto the chassis ril and is located vertically. This is the configuration of my GQ ARB bullbar.

Food for thought.
Phil

Also, its not good general practice to clamp 3 elements together with the same bolts for the reason above. I have designed and built a lot of machinery over the years and its a design basic we always used, except where the fixtures were non load bearing or not important for alignment or position.

[supazuk]

I hope there are more welds holding that plate on

it is fully welded however the weld just locates the plate, the chassis actually does the holding.

[Wambat]

Alistair,

Also, its not good general practice to clamp 3 elements together with the same bolts for the reason above. I have designed and built a lot of machinery over the years and its a design basic we always used, except where the fixtures were non load bearing or not important for alignment or position.

thanks phill, that is what i wanted to know, i need some one that knew more than i to tell me, so, crush tubes are still out, but bolts and washers should be sweet yeah??? one bolt may need a slightly bigger washer as i said earlier, the metal has been removed previously buy a grinder and is thiner, to the point in one spot its nearly sharp where the hole is,

although that is one bolt out of 8.... the rest are all good,


as re the quote of your post i used, like i said i had heard about it at trade sqhool, but thought it was the other way round, and that it was better, but i am happy to be prooved wrong, when it comes to this.



in terms of design of the bull bar its self, is there anything wrong with ending it at the end of the chassis so i have very little over hang?? i dont plan on mounting a winch to this bar, the onyl play in the eyelets for the d shackles,

and if i remeber correctly your not ment to have anything protrude from your bull bar are you?? so i would have to make it in a way it dosnt stick out, which has got me a little miffed at how to come up with it.

[Wambat]

this bar has what i am talking about, and general shape i am thinking of, but not practicle for what i want,

[fester2au]

The brackets on the bar on my 80 series are three sided - top, bottom and outside. Bolts through the side and the bottom but still only into the captive nuts which at this stage are still good. With the top plate the bracket cannot pivot.

As a fitter and turner could you not work out a way to drill out your holes larger and offset and still put in good solid crush tubes. That is what I would do. Also your original idea of tapping the inside plate and using nuts is not sound and neither is welding nyloc nuts in or for that matter mechanical locking nuts as they ewventually lose their grip so need replacing. Stainless bolts are not good as they are not high tensile, all they will do is not rust. Not sure whether Unbreakos have any additional corrosion resistance to unbranded high tensile bolts. Never particularly used them myself but I just thought they were a brand.

So to sum up if it were me I would offset drill the original holes to whatever size was needed to match the appropriate crush tube. You should be able to machine whatever size you want, say a step on one end to suit a smaller chassis hole fit them in from the larger side and weld them in place on the other side. Or weld them to a plate and fit through and weld that plate in place etc.
Say 3 bolts through the sides of the chassis rails and 2 through the top or bottom into say a captive plate to replace the captive nuts and that would keep your fabrication skills going and be plently strong enough. 12mm bolts through sides and 10 or 12's through tops or bottoms.

As far as cutting the drivers rail bits out plasma will be pretty neat but still depends on operator and if it's like ours at work you won't get right into the corner anyway. Find someone who's good with oxy like an older boilmaker and they should be able to cut those bits out very close to edge and very neatly.

[Wambat]

i think the difference in the off set would have to mean new holes, which wouldnt leave me enough meat on the chassis to be strong enough and may pull through, or such a large hole that i wouldnt be able to make the crush tubes properly, and also i am a fitter, but, was out of work for too long, and as i am young, i dont have enough experiance for any one to even think of putting me on, as out of 30 applications i didnt get one interview, which broke my heart, all of the potentiol employers saying we want some one with 5 - 10 years experiance after thier apprentice ship, well i cant get that without them employing me, so now i work in a super market, and i no longer have access to all the machines i used to have, so cant even machine up good crush tubes,


so with that not being an option, can i just go with more shorter bolts instead of less longer bolts and crush tubes, and get the same effect ( i would think so)

[fester2au]

Ah that makes life a little more difficult (all round by the looks) being a fitter I expected you had access to many good toys. I guess that is about all you can do. Mind you bear in mind the principal of the TJM ones that mine ae copied off and they still only have the 3 in the one side and 2 up from the bottom. But for pulling off couple more would not hurt depends how easy it is to get bar on and off and positioned correct when your mount is a box section sleeve over the chassis rail if I understand your idea correctly. The "C" channel shape like TJM makes it easy to get the bracket on and off and the bar then bolts to that bracket.

[Wambat]

well i plasma cut out the box on the drivers side rail, wasnt to hard, is nice and neet, and i am left with quite a thick section there now.

if i were to weld in a 5mm plate to each side of the inside, then bolt through that with washers, would that then be strong enough to be recovered from??? it wont allow the middle steel (chassis) to be ripped out that way???

i had a better look today and comitted the bolt holes to memory, there is no way i could have done the crush tubes, the holes are off set buy nearly 45 degrees.

i need to do something to the drives side rail on the lower hole that faces towards the center of the car, it is very thin, thinner than i first thought, and if i dont put something behinde it it will be a weak point.

cheers al

[Guy]

Plate the and weld outer edges, drill through at a right angle, put in your crush tubes, bolt on bullbar.

Simple really

Also put in a bracket running in a horizontal plane as well as the verticals .. will add alot to the overall strength ..

Also please dont snacth off you bullbar .. Snatchrecoveries should only be attempted off something directly attatched to the chassis.

[Wambat]

that is the point, the recovery point will be where the bull bar attaches to the chassis, using d shackls (as at the one of the strap on a vhicle is ok, but not when joining two straps is how i was taught), is what i want instead of the recovery hooks,

and like i have said previously for the original holes crush tubes are not an option, if i managed to make a plate for the inside of each rail, i could then drill extra holes, two at the back of the out side rails, and two at the front of the inside rails ne plate, and i could use crush tubes then, but i dont know if that would be good, i will do everyone a favour and take some photos with something through the holes so you understand how great the offset is.

[bazzle]

Dont worry re the tubes, weld a plate each side to reinforce your weak bits, drill thru into orig holes and just use nuts welded onto a bit of thin flat to hold in place whilst doing up. Ensure you use grade 8 bolts.

Bazzle

[Wambat]

grade 8, not 10 or 12???

just curious, as thats what i would have used


also while i was not sleeping last night(restless) something you guys said sunk in finally, without welding in a pate on the back to drill through, ie, just using washers, you would be faced with the same problem as with what i was orignially askign about, just having a clamping plate wouldnt you???

so captive nuts is the best way to have it like original??? so if i do weld a plate on the inside of the rails each side, and eld nuts to those plate, will it be strong enough to not pull through my chassi??? under normal circumstances not under my truck falling off a clif and using a snacth like a bungey cord...