Polyurethane has been with us as a specialised plastic for some thirty years. However recent advances have now made it possible to engineer very special properties into this exciting material. Suspension bushes are some of the most highly stressed components fitted to a motor car. They undergo enormous strains and in the most arduous of conditions with no maintenance or lubrication.
The material they are manufactured from is a rubber compound containing natural products which deteriorate with age. It becomes softer and more pliable, resisting the forces placed on it less and less. Therefore allowing more and more movement of suspension components and offering less and less control over the suspension geometry.
This in turn causes accelerated tyre wear, braking instability and poor handling. This is the single biggest reason you can instantly tell the difference driving a three year old car compared to a showroom new one. However even new cars will benefit from polyurethane bushes because of their superior design they offer much more effective control of the suspension components to a much greater extent than normal rubber items.
Some drivers consider polyurethane bushes on normal road driving to give too harsh a ride. This said there are always advantages and disadvantages. For example if you are prefer a more relaxed comfortable drive you would probably agree that poly bushes give a harsh road ride. If you are a fast road / race / track day driver you may argue the benefits far outweigh the disadvantages.
The debate continues and it will always be personal choice, one thing for sure is that there is plenty of research and material available highlighting the improvements over standard rubber bushings.
With the technological advances in this material it has been possible to overcome the common problem associated with harder bushes which is increased noise. By correctly engineering the polyurethane compound, bushes can be made 25-30% stiffer than new rubber items but with exactly the same noise absorbing properties. POLYURETHANE bushes make sense.
- POLYURETHANE for prolonged tyre life.
- POLYURETHANE for improved performance.
- POLYURETHANE for increased safety.
Here at FLASH CUSTOMS we recommend POWERFLEX Poly Bushes
Note some of the above information has been taken from the POWERFLEX website
Thanks for reading :)
Now days on the vast majority of road going cars and vans a crankcase breather system or crankcase ventilation system is used to improve emission levels. In order to affect a controlled system a PCV (positive crankcase ventilation) valve is used to monitor the pressure in the crankcase and as this becomes too high this valves releases the excess pressure into the intake system. One thing to understand is that all internal combustion engines “leak” a small amount of combustion charge past the piston rings. When introduced into the intake system (via the PCV valve) this charge of leaked combustion gases will generally reduce the main intake charge or fuel and air mix, thus reducing the efficiency of the intake charge. This will cause loss of power and in worse case scenarios “pinking” and “detonation”.
It is common knowledge that all internal combustion engines (even when new) will have a certain amount of “blow-by” past the piston rings (a mix of acids and water vapour – combustion by products), which if left stuck in the crankcase will increase crankcase pressure leading to issues affecting the engines performance such as:-
- Reduced efficiency of oil scraper rings – creating increased oil consumption
- Starting problems and uneven idling or “rough” tick over.
- Blow-by gases causing oil contamination, “sludging” and increased engine wear.
- Weakened fuel charge, causing ignition retardation and power loss.
- Blow-by gases will escape through the easiest route possible – filler cap, dipstick or blow past oil seals.
All of the above may affect engine efficiency and performance.
On understanding the above you may now realise why a good breather system is needed on a race or high performance engine. In general terms for this application any “blow-by” gases are taken away and not fed back into the intake system but directed to a dedicated “oil catch tank”, sometimes known as a “breather tank”. This way the crankcase gases are filtered through baffles and oil, waste contaminants and pollutants “settle” to the bottom of the tank whilst cleaner air is then passed through a filter back to atmosphere.
Sometimes this oil and contaminants from the catch tank can be fed back down into the sump to be mixed with existing oil, its important to remember if this is the case the returning oil must be returned to the sump at a level below the normal level of the oil in the sump, this is because if it was returned above this level the positive crankcase pressure would blow the oil back up the drain pipe back to the catch tank. Obviously draining oil back to sump will create the need to change the oil much more regularly.
This blog is aimed at giving a basic understanding of a PCV breather system; in reality this system is a little more complicated in its operation but I have tried to simplify it to aid understanding.
Thanks for reading :)
A Customers Honda Civic VTEC Engine cover Modifications came about due to the need of an improved oil breather system. Here as you can see we have added 2 x Dash10 alloy fittings to the side of the cover to improve the breathing system. These will be connected via a hose system to the Oil Catch Tank. This Tank build is posted previously in our blog – click here to see it.
Improving the breather system is a necessity on the engine as it has had various internal mods and turbo-charging to boost power to a high 400ish bhp. To cope with this sort of power upgrade, has meant all other systems being upgraded to suit. The breathing system included. This now includes crankcase and head breather additions piped through to an oil catch tank, which is baffled, with collected oil draining back to the sump.
As you can see we have TIG welded the two fittings onto the cover, sometimes TIG welding cast Aluminium can be unpredictable due to the nature of the material itself. Cast Aluminium is known for being “porous” and hence soaks up oil into the pores of the material. Until you heat the material (when welding for example) the contamination within the material will “burn out”. This process can leave a poor quality weld as if all the contaminants are not burned out or dont float to the top of the weld pool defects can be left in the finished weld – typically in the form of “porosity” or in the very least poor fusion between parent and weld metal.
In order to try to eradicate this problem on some castings I have been known to lay a first weld (to help draw out or burn out any contaminants), grind the weld back and then re-weld once “clean”.
We also have to be careful with cast materials when welding as they can crack due to the high concentration of localised heat in the welded area. It is therefore sometimes advantageous to evenly heat the material before welding. This then reduces the chance of “shrinkage cracks” upon the localised heat cooling. If the job has been warmed up or “preheated” prior to welding then the whole job cools more evenly and therefore there are less local stresses set up around the weld area as the whole job will “cool” and therefore “shrink” more evenly.
Note that we can usually modify cast aluminium sumps and covers, to any customer requirements, we have repaired smashed sumps and dropped engine cases, chopped sumps to improve ground clearance on race and kit cars, added sump bash plates to help protect them and welded in new fittings for breather take offs, oil take offs etc.
Thanks for reading :)
As highlighted in our previous blog, the need for an Oil Catch Tank. Not just any old oil catch tank, a properly designed tank will be much more effective at separating oil mist and vapours. In the past I have seen Oil Catch Tanks made from Tin Cans, Drinks Bottles, Plastic food containers and all sorts, by far the best option in effectively separating oil and vapours. Lets have a look then at manufacturing an effective Oil Catch Tank. Below we can see one of our “technical” (lol)
From our sketch we need first to produce a sheet metal cylinder. A couple questions pop up here immediately. We know size of cylinder we require (e.g. the diameter of the can 100mm) but we need to mark this out from a flat sheet of material (in this case 1mm mild steel). Hence we need to know the circumference around the cylinder to know how long the panel will be in the flat sheet state before rolling. We work this out using a simple formula – ∏ (symbol represents “pie”- 3.142) x diameter = 3.142 x 100 = 314.2mm (which is the flat length of sheet required before rolling up. So we will need a flat panel of sheet cut out 314.2mm x 140mm long (height). We can now go ahead and mark this out to size with a rule and scribe, cut out using a guillotine (or tin snips, or grinder and cutting disc) and de-bur (remove rags on edges) caused by guillotining / cutting – remember safety 1st – use goggles / gloves / personal protective gear! The next stage is to set up our rolls to roll a cylinder- in this case we have “Pinch Rolls”, which are particularly for sheet metal (up to 3mm thick). You may notice from the image above that Pinch Rolls are set up with 2 rolls above and below each other. These rolls grip the sheet material between them and drive it forward and back, the 3rd roll at the rear is adjustable up and down, this can then be used in turn to add pressure to the material being rolled through the top and bottom rolls and produces the pressure to lift the material and “roll” it into a cylinder. Obviously the more pressure added from the rear roller the “tighter” the cylinder diameter will roll up. A technical point to note then before rolling thin sheet is to “Break the Grain“, this is a process where the sheet is rolled one way then another, turn it over and repeat, offer sheet into the rolls at an angle and roll one way and then the other. This is only ever done to put a very shallow curve into the panel to remove any “memory” the sheet may have. This occurs when a sheet has been taken from the inner of the “coil” of sheet material as it is transported from the mill to be rolled flat and cut into manageable size sheets.
Most sheet comes in sizes of – 2m x 1m 2.5m x 1.25m 3m x 1.5m 4m x 2m, So before we roll our panel into a cylinder to form the main body of the catch tank we also need to check that the sheet panel is square, otherwise once rolled up into a cylinder one edge may be longer than the other. An easy way to do this is to check the corners with an engineers square. For larger panels it is just as easy to measure diagonally across each corner – corner, if the measurement is the same then the panel is “square” if not then it proves that the panel can in effect be a parallelogram; which we don`t want. Once “rolled” to the correct diameter we can clamp, tack and weld the joint which runs longitudinally along the cylinder – I use a “TIG” welder to produce a nice even – more importantly “leak free” welded joint.
See below Image of all parts to make the catch tank
So you can see the rolled shell, the domed bottom, flat top, angled baffle, perforated baffle plate and barrel fittings which will be cut in half.
Once all parts a made, the “tack” up stage can begin; tack up is important as all joints need to be a close fit joint due to the fact that the material is only 1mm thick this can easily be “blown away” by welding once heat has been built up in the joint.
Image above to the left shows the a bad tack up of the base of the oil catch tank to the main body. As you can see I have allowed too much heat to dwell in one point and not added enough filler wire and hence a small hole has blown through the joint. This was easily remedied by a small pulse of heat and a quick filler material addition to fill the hole.
The image above to the right shows the main body with baffle plate tacked in place to the back of all 3 inlets (inlet holes shown). The idea of this is that the oil mist hits the vertical baffle plate and is aimed towards the bottom of the tank where the mist hits the perforated baffle plate where oil will settle and drain to the bottom of the tank to return to the sump. Vapour will then head up and out of the top mounted filter where any remnants of oil will be filtered out before it vents to atmosphere.
Once all the parts are fully TIG welded to the main body of the catch tank I need to pressure test the tank to ensure that there are no leaks. This involves “bunging” up all the inlets / outlets with caps or tape, leaving one free to connect a compressed air line to. This is then turned on to add pressure to the tank (usually no more than 1bar) is sufficient. Once ready there are 2 ways to test – either submerge the whole job under water and watch for small bubbles leaking out of any joints or – brush all joints with soapy water (I usually use fairly liquid mixed with water about 10 to 1 ratio) and again watch for bubbles that the leaking air will produce. Both methods need a constant pressure to be maintained in the tank whilst testing. Any small “pin hole” will quickly reveal its self by a steady stream of bubbles appearing from the point.
I always test tanks of any description initially with about 1 bar of pressure, if they have brackets I will test the tank before welding on brackets and then up the pressure slightly and test again after welding any support brackets in place.
This ensures double checks are made and tanks are delivered to customers 100% leak free – in 10 years I have only ever had 1 petrol tank leak – one that happened to go to one of my longest standing customers, needless to say it was on his own personal race car and I felt like such a fool. None the less I repaired it by washing the tank out with a pressure washer and then filling it with inert gas (argon) to reduce any chance of explosion by any fumes that may still have been present in the tank. Job done. This is not recommended to be undertaken by anyone other than a “professional” as the tank could explode in your face while welding and cause burns and severely nasty injuries.
Once the tank was complete a bit of a clean up with an abrasive pad and a thin coat of oil was added with a rag to stop the tank rusting. This was because the customer decided he wanted to paint the tank to match his car.
Completed tank before painting –
I hope this Blog has been of some intuitive help to someone. If you have enjoyed this Blog please remember to sign up to receive updates every time a new article is added – see the left hand border for sign up information.
Thanks for reading :)