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About sexton

  • Rank
    Staff Sergeant

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  • Location
    Whitby, Ontario, Canada
  • Interests
    All things mechanical.
  • Occupation
    Mechanical engineer
  1. Fuel pump diaphram material

    Viton rubber is very good stuff with good resistance to gasoline and its ethanol additives. Do a google search on its compatibility for more info. If you google nitrile, aka Buna N, you'll find it's good for gasoline but not good for ethanol. I visited a sales rep at a local gasket company and he happily sold me some Viton offcuts for $30 which I have used successfully for fuel filter gaskets. (I volunteer at a military museum so I think he saw a potential market.) But fuel pump diaphragms are a different kettle of fish, needing to be thin for flexibility, but also needing to withstand high stretching loads and also thousands or tens of thousands of cycles. As said by an earlier poster, I suspect that is why fibre reinforcement is critical. Have you looked at electric fuel pumps? They bring a whole new set of challenges but there are good ones out there with built-in pressure control, a critical factor when using with a carburetor. Malcolm
  2. Down-sizing starter battery?

    My son has a Cummins straight-6 5.9 litre diesel in his 1989's truck. I was curious why the specified battery cables were so heavy so I measured cranking amps. 400 amps with the 12v starter. That is really high. So on a 24v system that starter would take around 200 amps. At that level of current, you have to make sure all the cable and terminal connections are clean and tight. malcolm
  3. Down-sizing starter battery?

    I keep an eye on batteries in our fleet of about 60 old military vehicles, including 5 Ferrets. Many of the older vehicles like the Ferrets have gas engines with low compression ratios around 6:1 which really reduces cranking amps compared to more modern cars with greater than 9:1 CR. And of course the 24v supply cuts the cranking amps in half again compared to a 12v car. So an old 4 litre Rolls Royce or Jaguar engine with a 24v system only needs about 100 cranking amps, maybe 150 in really cold weather. So the 700 CCA you get from a pair of decent 12v battery in series gives you a huge margin to deal with long storage periods, prolonged cranking to prime empty fuel systems, etc. The highest cranking amps I have seen are on more modern 30 litre diesel tank engines (400-500 amps). Jeeps are the lowest at 50 amps. WWII stuff like universal carriers and CMPs are high at 200-250 amps because of their 6v systems. I find most people don't know how to test a battery properly. Getting good voltage across the two posts means nothing. Good tests are: specific gravity of each cell after charging, load testing after charging at half the rated CCA, which needs a carbon pile tester (the load from the cheapy 100 amp heating element type testers is too low), and my favourite, the battery internal resistance tester. One benefit of good testing is you can keep even older worn out batteries in service by using them in low cranking amp vehicles like Jeeps. We have been buying Deka military batteries and have found they are crap. If they are discharged right down they just won't come back. However, I am really impressed with Pow-R-Surge batteries. Malcolm
  4. Ferret Fluid Flywheel Seal

    Going a bit from memory here, but the Ferret idle spec is around 500 rpm (although we find life easier setting it around 650 rpm). The fluid couplings seem pretty bullet-proof, so if the fluid coupling doesn't start to engage and move the Ferret around 800 rpm, we assume the fluid level is low. I must confess I use this lazy man's way of monitoring level. Since we use ATF in our fluid couplings, red ATF on the hull floor is not a good thing, even if the FC is working well. I had a Ferret that had a large rpm drop when put in gear at idle. It turned out it was just an engine tuning problem but leading up to that discovery, I experimented with fluid coupling oil. As-found was red ATF, which is about ISO 30. Spec is ISO 10 oil. So I switched to ISO 10 oil to see if the coupling would "drag" less at idle when a gear was engaged with the thinner oil. It made no significant difference, so we just use easy-to-get ATF in the fluid couplings. Malcolm
  5. Cleaning spark plugs

    We have no problem idling our Ferrets in shows for up to an hour, although I hate doing it. That plug looks a bit carbon fouled. One thing I find about old school plugs is they are sensitive to fouling. Two things worth trying: 1) screw in the idle mixture screws to lean out the idle mixture as much as possible without affecting idle rpm and off-idle response (check carb base for warping if you can't get a smooth idle), and 2) inspect accelerator pump diaphragms for cracking and leakage, which is common on Ferrets (this makes them run really rich). Malcolm
  6. Leopard 1 wiring diagrams?

    Thanks for the suggestions. Turns out others in the organization are concerned about our lack of wiring diagrams and are spreading their nets. I'll (thankfully) leave it to them! Malcolm
  7. Leopard 1 wiring diagrams?

    Well, Robin, going to KMW is certainly going to the source! In lieu of that, I've emailed Panzerfarm in Poland who supplied 2 of the Leopards to see if they have wiring diagrams. And maybe your source will come through. We've figured out the problem with the shorted glow plugs by disconnecting the 24V supply to the glow plugs. This now prevents a circuit breaker from tripping while cranking the engine and killing the start signal to the starter solenoid. Now it fires right up despite there being no glow plug preheat. We'll see how this works when the weather gets colder. The other Leopard run problem may be due to a feature where the engine is automatically shutdown if the coolant level gets very low or the oil pressure drops below 1 bar. May be legit. May be a bad sensor. Further investigation will tell. All the wiring has white braided insulation on it with wire numbers printed on it every few inches, which is a really nice touch. For example, the 24V supply to the two glow plugs banks is wire number 241-1. Having diagrams that show these wire numbers would be very helpful. Malcolm
  8. We have some Leopard tanks and various manuals for them but the manuals don't include wiring diagrams, which is making troubleshooting difficult since we have one that is tripping a breaker, probably due to a shorted glow plug, and won't crank, and one that is starting, running for a few minutes, and then shutting down, we think because of an electrical problem. Are wiring manuals available anywhere? Thanks, Malcolm Ontario Regiment Museum
  9. More Ferret woes, now oil leak!

    If you have confirmed the oil is coming out of the hull and not from a wheel station, it could be coming from the engine, the fluid coupling, the gearbox, or the transfer case. Oil leaks tend to run to the rear of the hull so you should see oil puddled on the floor underneath the engine. Engine oil tends to be darker, whereas gearbox and transfer case oil is honey coloured. Fluid coupling oil may be very light if you are using the spec ISO 10 oil or red if it's ATF. We have 5 Ferrets and I haven't seen any leak from the engine sump, probably because these are dry sump setups. We have one leaking engine oil from the exhaust valve cover on the RHS of the crankcase and one from the valve cover. We haven't attempted to repair these yet. Both repairs look fairly easy with the engine in place. One Ferret has a bad leak from the lip seal sealing a rear driveshaft where it enters the transfer case. It looks like this will require removing the transfer case to repair. Best way to determine the source of a bad leak is to see which component needs topped up most often. Malcolm
  10. Ok, thank you. Malcolm
  11. Thanks for the response. I'm not sure what "turn to the right" means. When looking from the front end of the barrel (the opposite end to the breech), does the locking collar turn clockwise or counter-clockwise to loosen? thanks, Malcolm
  12. Hi, we have a newly acquired 88 mm Flak gun with the three-piece barrel. We are attempting to unscrew the locking collar, shown below, from the barrel. A TM we found says this lock collar is left hand thread, but it's putting up a helluva fight. A YouTube video we just found shows a museum somewhere in Europe also attempting to remove the collar based on it being a left hand thread, and then they show the collar coming off by screwing it CCW, i.e it has a right hand thread. Can anyone clarify? Left hand or right hand thread? Thanks, Malcolm
  13. ferret poart wanted

    Jim, Couldn't you just make one? They're not very complicated. Malcolm
  14. John, the coolant leak was a 5 minute fix. After I dropped the big hinged hull hatch underneath the engine, I found the short coolant hose we had forgotten to tighten the clamp on after using it to drain the coolant a year ago. Classic example of what can get forgotten when it takes that long to get replacement parts (which was not Panzerfarm's fault, by the way). She ran pretty well in the Gulf war show last Saturday. I think the gearbox had synchro originally, but it doesn't now! The 1-2 shift is damn near impossible. In fact, I suspect first gear is a bull low gear, not designed for normal driving. You can start in second keeping revs up and easing the clutch, but it is easier to pull both tiller bars back to the first detent to get the gear steering reduction on both tracks (which approximates first gear) and then, when she's moving, push both bars forward to engage second. 2 to 3 is a nice shift, with the massive torque of the engine coping no problem with the speed drop during the double de-clutching. But the downshift from 3-2 is a bit balky. And you you gotta keep an eye on the coolant temp. The driver is solely responsible for this as there is no thermostat. When she gets up to the top end of the range, 100C, you have to operate the lever to open the radiator louvres. It's damn hard work and quite stressful! Malcolm
  15. Home-made inner chalices?

    That's possibility, David. Those "chalices" (so named because of their resemblance to the medieval cup, I guess) are an amazing piece of manufacturing and very hard to duplicate, I imagine. Malcolm