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|Posted on Monday, 06 November, 2006 - 06:14: |
I have just had a discussion with a work collegue about a hydrualic control problem we have with trim tabs on a speed boat.
What is happening is that the control lever for the trim tabs gets stiff as the hydraulic fluid heats up.
We noticed that the exsisting fluid is dirty so this is the starting place for the fault
One of the ideas was to change the fuild to something else and silicon hydrualic fluid has been suggested.
He has just got a reply from an oils expert who is a consultant for Lockhead amongst others.
He said that silicon fluids will foam badly when being forced though small opening such as pressure relieve valves which will result in overheating, pump siezure and eratic operation, he also added that Silicon based oil are not that good at lubricating which is the opposite of what I thought.
He has recommended Skydroll which is like autobox oil, Shell Tellus, or Castrol LHM.
Skydroll is used in aircraft hydraulics.
We selected Tellus because we have loads of it and it very easy to get and cheap.
So I have got it from the horses mouth do not use DOT 5 in Shadows. because the Shadow has lots of small opening such as the brake valves and valve bodies which will froth the oil up and the brakes will be eratic as the pumps try to compress the foam and it is about £25 per litre.
Which makes the proper stuff very cheap at £7.50 per litre
(Message approved by david_gore)
Post Number: 620
|Posted on Monday, 13 November, 2006 - 06:00: |
First your prob with hydraulic fluid running hot with the trim tabs system.
First the pump [not piston type as on a shadow] is your cause of heating under full loading at high revs.
Solution as is on mine is to use a heat exchanger running the sea water for cooling the fluid.
Regarding DOT 5 in a shadow pumps will will run at half engine speed.
DOT 5 is more compressible and foams and also outgases slightly below its boiling point it also can aerate from prolonged vibration.
This makes it bad news for any system with ABS.
Regarding the shadow it is still a testing time.
You can only go from dot 3/4 5/1 RR363 to dot5 with a good flush, but you can not revert back without changing all the seals boots hoses "o"rings so a good time to do it is just before a brake overhaul is due.
As the fluid may aereate this in my opinion will happen AFTER it has done its job through valves etc and will freely return to the reservoir.
As dot 5 is non hygroscopic and as a resault will not absorb moister however as water will get into any system in time the bleeders should be cracked for a small bleed every two years[water may pool at the lowest point calipers]but overall use of dot 5 may be kinder on the system long term!
Post Number: 669
|Posted on Tuesday, 14 November, 2006 - 14:58: |
We must agree to disagree here - DOT 5 has not been approved as an alternative for RR363 by either R-R/B let alone the fluid manufacturers.
In my considered opinion given the experience of Bill Coburn with the Aust. Government Phantom brake system as documented in TEE-ONE Topics; it would take a "very brave owner" [to paraphrase Sir Humphrey from "Yes Minister"] to use anything other than RR363.
I have reluctantly not censored the content of the previous post but sound a very strong warning to anyone remotely contemplating any change from RR363 to carefully consider the possible consequences especially from an insurance point of view should there be a subsequent accident caused by or contributed to by brake problems.
Post Number: 621
|Posted on Tuesday, 14 November, 2006 - 17:46: |
David,DOT 5 silicone has not been reccomended by any car manufacturer to-date, this is because the SOES j1703 has tested compatibility and measurment.
As brake manufacturers depend on elastomers to swell up to 5% to seal correctly.
Everything was engineered for glycol at the OEM level.
We all know that the problem with silicone was the inconsistent swelling with elastomers.
As the Shadow system is totaly different silicone may well be a way forward and to be approved by the DOT 5 manufacturers instead of RR363.
As i have stated in my previous post regarding the Shadow this is still as testing time.
Long term may well be kinder on the system.
Post Number: 797
|Posted on Tuesday, 14 November, 2006 - 20:29: |
Gosh Patrick this all reminds me of the old saying 'give them an inch and they'll take a mile.' Twenty years ago this forum would not have existed, at least in this Club. In the face of considerable opposition I started 30 years ago writing 'The Canberra Contribution' which was slipped into the New South Wales Branch newsletter each month. It dealt mainly with my amateurish struggles with doing a ground up restoration of my dear old Silver Dawn SDB94. I was determined to redirect the readers of the newsletter away from recipes, who wore what at the last gathering and the odd smutty joke!
The lawyers champed at the bit, 'what if' questions were raised, liability was on many tongues and disclaimers were judged to be useless. But I persisted until I took on the editorship of Praeclarvm in its present form.
George Shores who used to contribute often to Tee One Topics used the expression 'My Way' to hopefully make it clear that he took no responsibility for his advice! But now we muddle on here with a chutney of really helpful discussions along with an occasional bucket of nonsense. Quite often our resident professionals wax on in terms that I simply do not understand except that they are always couched as a litany of facts NOT advice.
Of course the post '85 cars (in Australia) moved into fantasy land for most of us and advice/directions/accounts particularly concerning the electronics are beyond Owner Joe or for that matter many so-called professional mechanics. But brake fluid in Shadows is generally comprehensible to most of us as long as you have passed at credit level 'Door Opening III' So the "'ave a go mate" reader could well read your advice and be in fairly deep detritus.
In short (thank God for that he says)stay away from radical steps in these columns, such as the use of silicone, in the interests of the good reputation (to which you have certainly contributed)we have built up over the years.
These are not fighty words just a request to restrict our licence knowledge sensibly.
PS If the above seems a bit liverish I have just spent the day extracting three burred over bleed nipples on the back hubs of an otherwise magnificent very early Spirit which has been serviced all its life by professional people including dealers here and in the UK. There is hope for me yet.
Post Number: 622
|Posted on Wednesday, 15 November, 2006 - 03:22: |
Bill, Yes of course there is hope for you and hopefully for testing all future mods confirmed by the brave in the first inst.
Long life antifreeze still on test,rear boot and crossmember strengthening in a way better than the makers mod, electric window mods by ?????????,
running on synthetic oil,varnish with cork plus much more i will leave out Cortina pads!.
To myself progressing through testing with the unknow is just that testing.
As i have said the Shadow system will cope in more ways than one and testing long term will i hope prove succesful.
Maybe this thread boat included should be under general discussion.
David the car that Bill worked on has wheel cylinders and master cylinders etc, not hydraulic pumps and calipers as per Shadow.
Post Number: 670
|Posted on Thursday, 16 November, 2006 - 12:55: |
I know that HOWEVER the master cylinder boots etc are common to both cars and if my memory is correct; the silicon fluid contamination meant they had to be replaced during rectification. I stand corrected but it is my understanding the calliper seals will react in exactly the same way as the drum brake piston boots as they are made from the same elastomer.
My main concern with the silicon fluid is foaming in the pumps or water contamination that is not removed by bleeding before an emergency braking situation where either the aerated foam collapses or the water boils leading to a partial/complete loss of braking capacity.
We must agree to disagree on this subject.
Post Number: 623
|Posted on Friday, 17 November, 2006 - 07:14: |
Cripes, first we are talking SS2 no master cylinder fitted.
There has not been any mention of this thread only being applicable to Shadow II vehicles.
As for the brake distribution valves upper and lower there are no boots seals just an interference fit with piston to body as per Citroen.
I deliberately did not include the distribution valves as I am well aware they do not have elastomer or other type of seal
No good on a citroen though because of the pump configuration.
A small leakage shown in the rat trap is just lube wastage with 363 or silicon.
A SS1 can have the backup master cylinder plumed with its own reservoir running 363.
Why bother when RR363 is cheaper than Silicon
Caliper seals with silicon are fine no need for the 5% expansion.
Has anyone measured the volume of fluid on the return of the system under full flow conditions,i dont think it is a gusher,no air so far!
To early to agree or disagree may the testing continue.
(Message edited by david_gore on November 17, 2006)
Post Number: 671
|Posted on Friday, 17 November, 2006 - 14:17: |
THIS THREAD HAS BEEN CLOSED WITH A WARNING THAT ANY OWNER CONTEMPLATING THE USE OF SILICON FLUID SHOULD CAREFULLY EVALUATE THE POSSIBLE CONSEQUENCES BEFOREHAND.