Member postings for Robert Atkinson 2

The thin gloves must also be tight fitting. If you are gettng within a thou or so of the moving part you are too close glove or not

Edited By Robert Atkinson 2 on 14/07/2023 19:39:07

Hi Frank,
POR-15 is a brand, not product so can't comment. On the Patina Preserver I'm dubious. Lots of buzz words but little hard data. It does say at the bottom " Clear protection lasts for approximately 12 months depending on conditions " this does not inspire confidence. If after 6 months it starts flaking off what do you do? Re-apply, strip it all off? It is also expensive.

Robert.

The most frightning thing I ever saw done on a lathe without an actual accident was at work. An older engineer parted off a bit of 1" thin-wall tube and then with it still running, wrapped bit of emery strip round his index finger and stuck it in the bore to smooth it. I could not say anything in case it distracted him. as soon as hiss finger came out I hit the E-Stop. When I asked him to think about what he had done he went very white and had to sit down....

There has been a Catalina / PBY over the village recently. Got a couple of snaps today. Not great quality, overcast, raining and shot from a window. Canon M100 and EOS-M 55-200.

My point is that in that circumstance the wire brush would have done the same thing without gloves.
Gloves are only a hazard when they are MORE LIKELY to be caught than bare skin or are STRONGER than bare skin. Tight fitting thin nitrile gloves are neither more likely to be caught or stronger than skin.
There will be edge cases, that I'm sure will be quoted, were the nitrile glove may be a little worse, but they are rare. That smal risk must be balanced against the hazards the gloves are protecting against.

So what gloves would you endorse? I did say "if you MUST have gloves...."

Robert.

The VFD does not care what the mains frequency is. I think you mean the base or rated frequency of the MOTOR. This is used by the VFD to calculate the correct output voltage for any given speed. If the VFD also allows input of the motor voltage rating you can use either 50 or 60 Hz as long as you also use the voltage for that frequency. If the VFD base voltage rating (not actual voltage) is fixed then you use the frequency for the motor that relates to that voltage.

There are two motor damage related limitaions on the maximum speed you can run a given motor on a VFD. First is mechanical and even if it is not stated in the available data a 4 (or 6) pole motor will run at the same speed as a 2 (or 4) pole of the same construction / model. Second issue is voltage spikes and harmonics from the VFD. Modern motors are more resistant to these and "inverter" rated motors have additional insulation.

Robert.

I was busy last night and missed this thread:

I recently fitted a 3 phase motor and VFD to my ML7 and after asssessing all the parameters I fitted a SIX pole motor and a larger (75mm) pulley on the motor.

The 6 pole motor is even smoother and quieter than a 4 pole, has more torque (for the same power) and the larger pulley is kinder on the belt. Even with tension off, the old belt would take a slight set around the motor pulley adding to noise and vibration when started.
It helped that the NOS 1/2 HP (0.37 kW) 910 RPM TEFC motor was only £40. A 1/2HP 3 phase motor is more than enough power for an ML7. The Gamak 6 pole I got is larger than a typical 0.37kW 4 pole to provide the torque so is very rugged.

The motor construction is identical to the two and four pole so is rated to the same speeds. Generally best use is made of a VFD when using it to run the motor at higher than rated (nominal mains frequency) speed. A modern inverter rated 4 motor will typically be good to at least 120Hz and a 6 pole to 200Hz but check the datasheet.

A two pole motor is not an viable option for the ML7. It's too fast and less smooth due to increased torque ripple. This can actually be seen in the surface finish of turned items.

Robert.

Any action that would cause a tight fitting nitrile glovedhand to be drawn in without tearing would almost certainly do the same to a bare hand.

If you must have gloves they are the best choice but must be tight.

Having had a coulple of older Fiats with the multijet engine I can tell you that they recommend 3 years as the maximum calender time between changes. As others have said low mileage due to short journeys allows contaminates to accumulate in the oil.
The DPF equipped Multijet engines don't have a mileage based oil change. The engine computer tells you when to ghange the oil based on usage. Part or this is because DPF regereration causes diesel to get into the oil reducing it's performance.

Robert.

If you've been chopping chillies both

Michael,

Did you see my post about using the head from a "long reach" type lighter?
These have the burner head connected to the tank by a tube. This may be easier to connect to say a blowlamp or gas stove tank and valve.
Additional benefits:
Easier to mount a small burner
Tank away from heat source
adjustment away from heat source
Adaptation under lower pressure
Adaptation not permanenty exposed to pressure.

Robert.

More to bump your post than anything, but:
How about a pair of bike brake cables for the regulator and a speedometer cable for the reverser? Whatever you do the regulator should be fail-safe to closed. Maybe just a spring at the loco end.

Or if you have a large budget I can design and build you a wireless servo control system

Robert.

If you get one of the long-reach disposable lighters they have a tube connecting the burner to the head. It would be easier and safer to connect the small tube to say an old blowtorch or gas camping stove.

Robert.

Mark,
I'm happy to be proved wrong but I've been working professionally with this stuff for years.

One thing is you refer to inverters, these are not the same as VFDs even though they may have a lot in common. Can you provide a model number for a VFD which can be used for unbalanced star connected loads? The point is that they are not intended to drive star or single phase loads so the electronic design and control software are not designed to support them. The phases are generally not independent of each other. All the current suppled by one phase must return through the other two. Most VFD inbalance protection is to protect the output devices not to protect the load from loss of phase. Inbalnce requires at least one phase to produce more power and excessive voltages. A device may survive inbalance when running at less than it's rated load (<33% for example) but that is not efficent.
Why do you use a Delta-Star transformer in your workshop?

Robert.

That is not correct for a VFD. There are number of issues. Firstly the VFD does not have a HF converter transformer and does not use balanced positive and negative buses. They just rectify the incoming AC to a single DC bus The topology relies on an isolated load.
Additionally the arrangement you describe will only work for a balanced load. Any inbalance between phases will affect the voltages so the "neutral" will not be at 0V with respect to all phases.
To provide a star output without a transformer requires active control of the star point (neutral) voltage. This requires it's own power driver effectively adding a fourth phase driver and additional control complexity.

Robert.

Sikaflex EBT+ in white or clear. Can be over painted.

Robert.

Welcome to the forum
:Bump

Robert.

The 1970 regulations were repealled. see

https://www.hse.gov.uk/pubns/priced/hsg17.pdf

Robert.

There are two problems with using a VFD to power aircraft avionics other than the safety of no mains isolation.

1/ The output is "delta"
2/ Harmonics from the PWM.

1/ means it is OK for balanced loads like fans but most avionics need a neutral return. It can be solved by a delta star transformer. This also fixes the isolation issue.
2/ needs a filter, maybe just series inductors, but may be specific to the VFD model.

Been there, done that.

Robert.

There was a discussion on a similar desin on here a while ago.

Wavey thing = swashplate