Suspension – Springs & Dampers - do not confuse spring rate and position of adjustable spring seats.
The spring rate is measured in lbs/inch. Thus a 500 lbs spring will compress 1/2 inch if a load of 250lbs is placed on the spring, 1 inch with a load of 500lbs, 2 inches with a load of 1000lbs and so on.
The length of the spring will control the ride height. If the ride height is low then screwing the spring seats up will raise the ride height. (The spring rate cannot change) as you move the spring seat up the body the tube in the shock absorber extends. The load on the spring has not changed (the weight of the car is unchanged) and the length of the spring does not change. The position of the spring seat has changed and as the spring length has not changed the position of the top mount has moved up.
If you run out of adjustment on the spring seat then a longer or shorter spring can be substituted but keeping the same rate.
This analysis fails if the damper runs out of length. A simple way to check that the damper has sufficient travel is to remove the spring from the damper, fit the damper to the car and with a jack lift and lower the car observing how the damper travels. Ideally on full bump the bump stop on the damper should prevent the chassis from bottoming on the road. On full droop the damper has sufficient travel to allow the wheel to fall to a reasonable position. Ideally on full droop there should be some pre-tension on the spring so that it does not rattle loose on the seats.
On full bump if the bump stops do not prevent the chassis from bottoming it is possible to position the bump stop with 3mm nylon C Washers (shims) that clip on the damper piston.
Nylon C Washers (shims)
If on full droop the spring does rattle loose helper springs can be fitted. These flat section springs have a very low rate and as soon as the weight of the car settles on the spring the helper spring collapses to a flat coil. Without the weight of the car the helper spring exerts just enough load to keep the main spring and seats in place.
As well as controlling the ride height the position of the spring seat also affects the load on that corner of the car. This is why competition cars have their corner weights adjusted either on corner weight scales or with a corner weight checker.
The weight on each corner needs to be a proportional spread of the total car weight.
Suspension - Corner Weights and how to adjust.
As we have discussed the position of the spring seat controls the ride height. It is possible to adjust the spring seat such that the ride height is greater on one corner. This means that this corner is carrying a greater proportion of the car weight. In fact what happens is that diagonal corners carry a greater proportion of the weight and the other diagonal corners a lesser proportion.
If the proportion is unequal the car is not balanced and may not brake in a straight line and may corner better in one direction better than the other.
Correctly adjusting the corner weights will remove the problem.
First the weight on each wheel is measured. This can be done with electronic scales or a corner weight gauge . The anti-roll bars must be disconnected when taking these measurements.
Total TW = LF+RF+LR+RR (LeftFront + RightRear etc)
% Front = (LF+RF)/TWx100
% Rear = (LR+RR)/TWx100
To check %front + %rear = 100
%Right = (RF+RR)/TWx100
%Left = (LF+LR)/TWx100
To check %right +% left = 100
Then calculate what the ideal weights should be
LF = TW x %Front x %Left
RF = TW x %Front x %Right
LR = TW x %Rear x %Left
RR = TW x %Rear x %Right
It is not necessary to measure the weights in any particular unit, all that is required is a comparison.
The spring seat positions are then adjusted to give the calculated weights. When this has been done the ride heights can be adjusted by moving equal turns on the adjuster seats. The corners have to be adjusted in pairs, either side or front or rear to keep the proportions correct. (not diagonally)
Finally the anti-roll bars can be reconnected ensuring that they have no preload.
How to extend the life of your electrical oil pressure sender
Protecting Oil Pressure Senders
Often electric oil pressure senders are bolted straight into the block and subjected to engine vibration which can shorten their life. A solution to this problem is to mount the pressure sender somewhere where it is protected from vibration (on a bulkhead) and connect it to the block with a Goodridge 600 series hose and unions. Sometimes this is necessary as there is insufficient space to accommodate the sender on the block.
Parts you may need :-
This union can be used if both a warning light switch and an oil pressure gauge sender are needed. The threads are all 1/8 NPT. For customers with other sender threads we can at our workshop drill and tap new threads.
This union can often be used where only an oil pressure sender is needed and the thread on the sender is M10 or 1/8NPT.
What’s the best location for fitting oil temperature senders?
Oil Temperature Senders
Occasionally a customer will tell us that they intend to use a T piece on the oil pressure sender as mounting for an oil temperature sender. This is not a good idea as there is little oil flow at the sender; the temperature sender just ends up measuring the temperature of the T piece which is of course mounted in mid air.
The oil temperature sender needs to be mounted where it will be surrounded by oil. This can be in the sump; a sump plug can often be drilled and tapped, or if the car is fitted with an oil cooler, a housing can be fitted into one of the flexible cooler lines. If fitted with a remote oil filter head, there is a boss on the head that can be tapped or the head can be supplied with the boss ready tapped.
On engines fitted with dry sump systems the sender can be fitted to a boss at the bottom of the dry sump tank. The Lazenby dry sump tanks are in two parts and can be separated for cleaning and thus also for welding bosses.
Parts you may need :-
Temp Gauge Adapter - Dry Sump Tank - Remote Oil Filter Head
The demand for these gauges has increased in recent months. The Stack ST3401 produces very useful information on fuelling giving Air/fuel or Lambda. It incorporates a WOT (Wide Open Throttle) peak function. This function allows a visual alert to be entered in the gauge to warn when air/fuel mixtures are running dangerously lean. A switch (not supplied with the gauge) is needed on the throttle. It is also possible to recall the peak reading on a run. The gauge comes with a Bosch sender and the output can be used as a feed to the ECU.
Stack Gauges – we’ve increased our Stock
We’ve had a huge amount of interest lately in Stack Gauges and Dash displays. In particular the Pro Control gauges which feature user settable alarms. And the ST700 Dash Display system , one of the smallest dash displays available on the market which can read RPM, Speed, Water Temperature and Oil Pressure all within an 80mm diameter circular casing. Due to high demand we have vastly increased or stock of all Stack Instrumentation.
The Learning Curve
Motor racing or farming? – Know Your Unions!!
Customers bring us their problems every day, some we’ve seen before and others are completely new to us. In our new feature ‘The Learning Curve’ we’ll pass on the solutions. Some of these problems may be familiar to you and if so then hopefully we’ll help you to fix them!
This problem was from an engine builder. He had built a dry sumped Ford engine; it was good on the dyno and it was sent to the customer. The customer reported that it had run the crank after a very short time running. The engine builder rebuilt, dyno tested and returned it. Again it ran the crank after a few minutes. After the third rebuild the engine builder asked the customer to supply all the dry sump lines and tank from the car so he could run the engine on the dyno with the parts from the car. The problem was then apparent.
The cause was the male/male union at the bottom of the Dry Sump tank. It was a union that had been found in a rush and looked like it had come from a farm machinery shop. Although it had the correct threads the hole in the middle was small. (Hydraulic machinery uses high pressure and low flows; car oil systems use low pressure and high flows). If it had been used on the pressure side it would probably not have caused a problem but on the outlet from the bottom of the dry sump tank it offered a restriction. The pressure pump on a dry sump engine sucks the oil from the tank, the rotors then generate the pressure to force the oil through the oil galleries. When the oil is cold it does not flow well and the pressure pump has difficulty in drawing the oil from the bottom of the Dry Sump tank. This is why the feed from the bottom of the tank to the inlet of the pressure pump is normally in hose at least one size large than the pressure hoses. Now we all know to check that there is no restriction in the adaptor. The union can always be drilled out or streamlined in a lathe. The other point to watch here is to use a hose with a stiff wall so that it does not collapse under the vacuum generated by the pump sucking. As ever, attention to detail and understanding how the system works is key.
New in at Merlin
Willans Harnesses - as worn by Jenson!
Willans are now supplying harness to Braun and Toro Rosso F1 teams and at the clubman level have introduced a tow strap and mounting eye to the new regulations.
Bell Racing Helmets
Merlin will soon be able to supply the full range of Bell Racing Europe car and kart racing helmets. Initial stock arriving in August.
Bell have over 50 years of experience designing and manufacturing car racing helmets and offer a complete range of helmets incorporating innovation, comfort and performance that exceed the toughest test standards.
In September 2008 Bell Racing Europe was the first manufacturer in the world to certify and produce a child’s kart helmet that meets the new Snell-FIA CMR standard. This standard will become mandatory for all under 15s competing in CIK FIA events from 1st Jan 2010 and is currently being evaluated for cadets competing in MSA kart events in 2011.
Bell helmets are available with or without Hans® posts fitted.
The range starts with the classic designed entry level Sport 4 (£309.08 +VAT) progressing to the Carbon/Kelvar/Glass (Tri-weave) shell RS3 Sport (£378.51+VAT), then the Ultra Series with Carbon/ Kelvar shells which includes the Votrex 2 (£660.50+VAT) and RS3 Ultra (£927.27+VAT). Finally the top of the range HP3 Advanced carbon helmet (£2163.00+VAT) which are now mandatory in Formula One.
Millers Engine Oils
By popular demand, we are now stocking some Millers engine oils to complement the Millers Fuelling additives we have stocked for years. We currently carry 10W40 and 10W60 CFS Fully Synthetic engine oils for tuned engine applications. And 20W50 Semi-Synthetic engine oil for more classic engines such as Austin Healeys and Triumphs.’
Be your own Stig!
With the current series of Top Gear in full swing, we are continuing to receive orders for Stig related items. So, this month we have a limited offer on Alpinestars GP Tech race suits in Silver. The GP Tech suit is ‘the’ suit which dons the Stig when he is pounding around the Top Gear test track. Featuring 3 layer Nomex construction but remaining extremely lightweight, this FIA Approved suit is ideal for racing and for posing! This offer is on for a limited time only and on limited sizes.