Posted From: 18.104.22.168
|Posted on Saturday, 06 December, 2014 - 10:11 am: |
I did a pipe work general training module in the 60s and this takes patience and dexterity to get it perfect.
Cars have pipe work every where from the exhaust to screen washers and everything in between.
The flexible bits are relatively easy. The rigid bits are very much harder to fit.
If restoring any car one needs to be friendly with a local pipe and thread guy. Because without him no pipes and no car.
Clips everywhere there are pipe clips these can be a PITA to remove and often one ends up cutting the clip off. If the self tapper won't come out and access is good enough I grind the head off then try to remove the stub, the grinding heat helps. If not then grind flush and fit the clip alongside. To make a hole in steel less than 16swg use a sharp spike. This pushes the edges of the hole in and gives a better grip on the self tapper. If the panel is large say the floor pan and the position is not well supported then it's best to drill. I have a selection of spikes the spike bit is slender then has a step so that it stops at about 4 mm in giving a 2 mm hole. I have a short one with a 90 bend in it for daft places to put a clip. MG Midget to remove the front to back fuel and brake pipes needs the gearbox out but the engine has to come out as well Which means the rad has to come out. But the bottom rad bolts are rusted solid and the captive nut has sheared off. If the front panel and wings are removed then the bolts can be got at. Which is why the pipes got re-routed. Also use Zinc plated hex head screws and grease.
If access is difficult then often buy using a sharp cold chisel the clip and screw can be forced out. Which means that either a bigger screw is needed or the clip will have to be fitted in a different place and maybe an extra one the other side.
The clips are important and must not be left off.
Where rigid pipes are fitted from subframe to body without flexible pipes. Attention must be paid to pipe clipping points. Because the mountings may flex. The designer will have designed the clipping points so that the pipe moves with the subframes. So closing up the gaps by putting say an extra clip in the middle may cause pipe damage.
Pipes can make noises and transmit noises. So careful when selecting new clips, a rubber is probably important if originally fitted.
selection of materials. This is easy but some often some how get it wrong.
pressure, temp, internal fluid and external fluid are 4 criteria used for selection of appropriate material. A 5 could be cost. This is derived from Pughs Model.
Copper based alloys are an attractive solution because they are not expensive easy to form and good corrosion resistance in car applications. How ever not all copper based pipes are equal and advice from the pipe guy is important.
Stainless steel. Stainless needs specialist knowledge to make sure the correct stuff is used. Even more so than copper. SS can suddenly fail especially on bends. SS requires good quality equipment, hammering a ball bearing in the end with the tube clampped in a chuck doesn't work. It works well on copper aluminum and steel based metals.
Big pipes such exhaust can be flared with a ball peen hammer. Support tubs in v of an axle stand and tap the inside out at a angle. Once spread a bit use a 2"/50mm tow bar ball hitch as a dolly then plannish.
Bending pipes. Small stuff will bend by hand. However much nicer bends are made by using a pipe bending pliers, plus these achieve tighter bends than possible by hand. Over 10 mm od hand bending usually kinks the pipe.
Aluminum piping on cars is rare. I don't no why because aluminum is used for heads radiators etc.
Pressures is obviously the first consideration in what material. Brakes is 3000 psi. Power steering is 1000 psi. Transmission cooler is 100 psi aircon is 1000 psi. Fuel carb is 10 psi. Fuel injection 200 psi. I use these generous figures as a general guide to get the right material.
Bundy tubing. The word Bundy is often misused to describe brake pipes. Bundy tubing is made from steel tape that is then rolled 720 degrees ( twice round a mandrel) into tube then resistance welded. This can be seen when a rusty bit is bent up a bit.
This stuff is now more or less obsolete. 3 choices modern steel, stainless and good old standby cunifer or kunifer.
Cut and shut. This method is used only, in cars that is, for exhausts. It is suitable for angles( bends) up to 20 degrees. The round box on my car has a gas welded cut and shut bend on the entry pipe. A 90 cut and shut would be restrictive. So when bodging up the rear section because one hasn't got £500 spare for a new one only £20 for a length of 60 mm mild steel exhaust pipe. Then design the bodge carefully to avoid sharp bends. And then save up for a proper one.
It's a simple concept, that hole there is connected to that hole over there taking the scenic route around the back of the engine. If the original can be extracted intact and not all bent up then it's easier. But old cars don't play the game. To get a good idea use 1/8 welding rod. The rod is the centerline of the pipe. Often make one rod then make a better one from the first. The rod will only take so much bending around before its a mess. Once the shape is right copy with proper stuff. This works with exhausts however tack the exhaust tube only then fit and then weld fully any hint that something got knocked out of line then stop welding and check fit on car. I usually end up fitting the bits many times to get it right.
Sometimes the pipe was fitted originally to the body before a major bit was fitted ie rear subframe or cross member. Which means the pipe has to be shaped in situ. Typically the rear rigid brake lines over the rear axle on a SY. I like to take the pipe out by cutting in half. This gives me the length. I add 1/2 inch. Fit the ID color sleeves tube nuts flare and then push the sleeves up behind the nut and maybe gaffer tape so that the nut cannot slide up the pipe and get jammed up with the pipe hanging half in because it's a pita. Then feed the pipe in making sure the pipe is going the correct side of other stuff. This often requires the pipe to be gently bent and UN bent. Once the ends and the middle are in the right place do the final bends with the pliers ( £5 to £10) to give nice tight correct radius bends. Loose fit pipe in unions. Refine the shape. Then tighten up.
Flairing. Follow the instructions plus fit the flare to a union and overtighten a bit this will bed the New flair. Do this on the bench. If the bugger leaks on the car. Overtighten by say 50 %, if it still leaks then start again pita. If it seals then back off to correct torque. This is a engineering judgement call on how much overtightening. It must not be left over tight it must seal at correct torque. This can bite you in the a##e at a later stage.
I never criticise pipework that is not perfectly striaght. If probably wasn't when it was new. Because to get it perfect is a double pita.
Pita. The best way with Pitas, is to know that before the job starts and just accept that patience and time is needed and tomorrow's another day. Consul yourself with how much a garage will charge, they will also think pita.
I hate pipe work but my pipe guy has lots of stock and a full selection of unions and clips. He makes life much easier. In general the prices are reasonable. He aalso does thread recovery and helicoiling. This sort of engineering shop is common in the UK., and probably the rest of the world. Keep them sweet.
(Message approved by david_gore)