Hlgeorge had posted a compressed copy of my PDF file, post #14 above, and was then nice enough to take it down at my request (the compression had very, very slightly degraded some of the pictures. You can hardly see it, but I''m a nut about such stuff).

Anyway I hope to work with him to get the PDF re-posted quickly. If you have already downloaded the PDF from his post, what you have is OK. Probably only I would notice the effect of the compression.

 

Dennis,

I snagged a copy of it before it was taken down. Copy looks fine to me. You should soon have the posting requirements for full access to everything.

I also made note of Testpoint's well thought out installation which is exactly what I will do. I want to preserve any of the original connections I can. I am waiting for the resistors to arrive and I'll convert my XK8 as soon a they arrive. I'll add any comments here after installation and my own testing.

Best,

 

As "stevetech" is doing above, I have ordered the resistor and will be adding it as shown in "testpoint's" photo. I will post my results when I complete the retrofit.

 

this is great information. I have the upgraded hoses that should handle the full pressure, unlike the junk Jag put in the car but makes sense to add insurance for a couple of bucks. I look forward to seeing where this progresses.

BTW I recomend the hoses for anyone that does blow, they really seem like high quality.

 

As requested, here is a re-post of the resistor procedure in a better resolution.

PLEASE SEE POST 54 FOR THE LATEST UPDATE.

 

Thanks to Hlgeorge for reposting the PDF. Anyone who gets interested in installing the system described there should also see post #18 above for Test_point's improved method of introducing the resistor(s) into the circuit. I'll build that idea into the PDF at first opportunity, but I'm afraid that won't be before the last week in September.

---------------------
Dennis
2001 XK8 Conv. (Titanium / Oatmeal)

 

Not wanting to get into this debate..but Dennis you wanted the PDF taken down because, as you put it, the compression had "very, very slightly degraded" the resolution?!?!? Seriously? But you are ok with it not containing test points improved method of installation. Just find that odd....

...now back to the pissing contest, err I mean, debate.

 

Let me try to 'splain this one for you.

When I get back home, I'll be rolling Test-point's excellent suggestion into the PDF and republishing. He's fine with that, last we talked.

HLgeorge had posted the current PDF for me because my "new guy" priveleges did not permit it. He compressed the file to get it under a file-size limbo bar, and in so doing a small amount of image clarity was lost. He worked some more on it and found that a lesser amount of compression did the trick.


Debate? There's a debate?

Dennis

 

Lmao.

 

You guys are tooooo funny!!

 

After 10 days of operation with the 0.20 ohm resistor installed I am happy to report that everything is working fine. Counting a few 'test' cycles I must have lowered and raised the top 25+ times. While a stop watch will document a 2-3 second longer lower operation time, and a 3-5 second longer raise time, I have become accustom and it just feels 'normal'.

I know covering the 'air mounted' resistor with shrink wrap tubing will only serve to retain heat. After I measured the resistor temp rise with a IR thermometer during multiple operational cycles without a problem, I covered it as an 'alarm' of harmful, and potentially dangerous over heating. No signs of any deformation of the tubing so heating should not be an issue.

Did my own research which did not identify any harmful affects of lower voltage on a DC motor as long as it is not stopped.

Guess I would have to say that what appears to be a viable solution to a huge problem has been solved for $10.

Thanks Dennis!

 

Good to know Dennis! My resistor has not arrived yet. I was thinking of covering the resistor add-in with the plastic wire loom cover. It won't fit real tight and has a slit on its length, so would not hold in heat, but keep it insulated from any metal bits.

 

Lew,

I hope Test_point or someone handier than I sees your post. I can't quite picture the material you're describing.

But it does seem to me the mounting requirements should be met by what you described ... let the resistor breath; keep things electrically isolated from ground.

To Test_point: Anything further I should have from you before folding your mounting method into the PDF? (I think I'm OK, just checking ... ) Should get it done by early next week.

Best,
Dennis

 

Some Corrections:

When something incorrect about the Voltage Reduction system is posted on the forum, I make it a point to post a correction. Two recent items need attention:

* Motor stall: a recent post claimed that Voltage Reduction shouldn't be used because stalling a DC motor can harm it. Since the Voltage Reduction system does not operate the motor anywhere near a stall condition, this objection really has no meaning. (The system operates at 8-9 volts. Testing during system development ran the motor all the way down to 6 volts with no stall occurring. No user of the system has reported a stall.) That the electric motor can operate across a wide voltage range seems to strike some here as mysterious. It's really a very common thing. Examples range from your old Lionel train to a PC cooling fan to the motor powering a Tesla roadster.

(An aside on motor stall: *some* motors don't tolerate stall very well; others can do so all day long with no problem. The most familiar are motors in reel-to-reel tape decks which can sit motionless for hours holding tension on the tape until called upon to do something else. Anyway, stall-tolerance does not matter for our system since we never operate near a stall condition.)


* Pressure reduction: the same (I think) recent post denied that the Voltage Reduction system reduces pressure; never mind the measurement data and user experiences. It seems pointless to push on this string again, better I think just to refer readers to the record made up of the posts here, those on the Roadfly forum, and the PDF file describing the system.

BTW, it *would* be truly mysterious if we could build a rotating fluid pump that made pressure independent of the torque driving it, or an electric motor that made torque independent of its voltage supply. Such devices are pretty much excluded by underlying principles; they would represent a sort of engineering "free lunch". The Voltage Reduction system works because it lowers the motor's voltage source ... which lowers the peak torque that the motor can make ... which lowers the peak pressure that the pump can make. There's not an ounce of mystery in it.

 

Seems like you are just begging for a rebuttal from one of the convertible hydraulic system gurus

Doug

 

Quote:

Originally Posted by Dennis07

BTW, it *would* be truly mysterious if we could build a rotating fluid pump that made pressure independent of the torque driving it, or an electric motor that made torque independent of its voltage supply.

I thought that current together with voltage determine largely torque, so low voltage/high current = high voltage/low current.

Really don't want to bash the solution you have developed, I just love low cost solutions, but I think what is needed is someone with knowledge in the field to prove that it is a solid solution imho. I asked a well known manufacturer of hydraulic pump systems about a low voltage solution to lower the system pressure, and the 1st answer was in short "use a pressure relief valve”. So I asked again “why” as I have been told that it should do the job, and this time the answer was more adamant, again “only way is to use a pressure relief valve”, didn’t dare to mail back…

As a heads up, I think it would help if someone in the know can explain the voltage/current part, as it is not just voltage here that counts (I can’t explain) and next someone in the know in the DC pump motor field that can confirm the voltage/current effect on our specific pump to know it is safe to use long term this way.

I have chosen the pressure relief valve, and would do again as I don’t like a difference in operation time, prefer the industry standard to control pressure via these valves and also appreciate the time/tests with graphs Gus has produced, as that gave me confidence the system will continue to be operating the same, and without any side effects guarantee a lower peak pressure.

Nevertheless as said, I appreciate that you try to find a low cost solution!

 

I no longer put dogs in these fights. There is a forum sub-culture that likes to take up this cause so I'll leave them to their devices.

I am not looking to compare technical "talking points" of the two options anymore, but commenting strictly on the motor, I am not concerned about the DC motor voltage reduction. This motor only runs for 15/20 seconds at a time, typically, with longs rests in between. I'd probably part ways if the motor ran constantly...I think. I also am not concerned about a longer cycle time. 15 or 20 seconds cycle time simply does not matter.

I am still waiting for the resistors to come. Mine must be on the "sloe" boat. When I get them I'll install on my own car and will satisfy my own curiosities, what is left of them.

The only comparison I will make of the two systems, and this might be unique to me, is cost. Many of my XK8 customers have cars that are now 14 or so years old. Some of them are reaching "jolopy" status with 100K miles and more. Cost of repairs is a large concern on a car that old. The delta in cost of these options makes both a choice my customers can make. I also have access to any system replacement parts, including the pump motor at far less than new dealer parts costs, so even if in the unlikely event some catastrophic failure occurs, I can still recover for less than the cost of the hydraulic solution...all in all, the risk here is worth it for my situation.

As with changing transmission fluids and using commercials brands, and other controversial repairs and maintenance, I apply my own standards and tests, then make recommendations to my customers based on that confidence, along with all "risks" that might be part of it. My customers then make up their own minds.

 

Avos,

You are correct ... voltage, current and mechanical load are all interdependent. This relationship is best captured in something called a motor torque curve (really a family of curves, one for any given voltage). There is a discussion of this buried in an old Roadfly post of mine, but I'll repeat it here in a day or so when I can. If you Google "electric motor torque curve" you'll see what goes on. 2nd year electrical engineering students roll around in this stuff if they study motors at all (sadly, not all do any more.)

I do understand that pressure relief is the industry standard fix for our problem. At least part of this, seems to me, is that you can go to a Grainger store and ask for a 950 PSI relief valve. You cannot ask for "the amount of electrical resistance that will reduce pressure to 950 PSI". That we had to work out by analysis and experiment for this particular system.

 

I am not claiming to be an expert in either hydraulics or electrical systems, consequently, I do not have the knowledge to dismiss the electrical solution as one that might work.

However, I do have a decided preference for the pressure-relief solution based on my engineering intuition and it is this. The LSI solution directly targets the problem--excessive pressure. The valve has been carefully calibrated to bleed off this excessive pressure at some specified level (xxx psi). I know that a week from now, a month from now, a year from now, with the engine running, with the engine not running, with a strong battery, with a weak battery, etc. that the pressure will be bled off at xxx psi.

The resistor solution is indirect and I do not believe it has the constancy of the pressure relief system. From what I have read here and on the other forum is that the resulting reduction in pressure depends on whether the car is running or not and the condition of the battery.

If price were taken out of the equation, I think it is pretty clear which system is better. So really it is coming down to price as to why someone might choose the resistor solution. Time will tell if the initial savings makes sense in choosing the resistor.

Doug

 

So really it is coming down to price as to why someone might choose the resistor solution.
Doug[/quote]


Yep......price is the reason. Simple when you boil it down.

And, my resistors came today...finally.