Russell McMahon
  • Member for 6 years, 11 months
  • Last seen this week
What does the word "pararail" mean?
2 votes

If this was a quiz show and you had one guess, the safest offering may be 'The suspension system in a vintage Scorpion snowmobile", BUT "Para rail" and "pararail" are 'made up' words usually used as ...

View answer
Is the fill factor of a photo-voltaic cell constant?
2 votes

Fill Factor is important for PV (photovoltaic) cell and panel designers but of less direct importance to users. What is usually more important are the practical parameters which result from a given ...

View answer
What materials can I use for the roller and band of a DIY Van de Graaff generator?
2 votes

As well as mechanical properties and lack of conductivity you need a means of creating the charge to be transferred. The following table gives the relative amount and the polarity of charge generated ...

View answer
Optimizing return temperature in a brazed plate heat exchanger
2 votes

As stated the problem is probably not well enough constrained. Given the specification, the way you get minimum temperature out is to pump as much volume as you can through the primary and then ...

View answer
Is there a way by which one could determine the required temperature difference for stirling engine?
1 votes

$$\text{Absolute maximum efficiency} = \text{Carnot Efficiency} = \frac{T_{hot}-T_{cold}}{T_{hot}} $$ where all temperatures are expressed in degrees Kelvin (= degrees C + 273). A very well built and ...

View answer
How high will a flywheel catapult launch a payload?
1 votes

As an upper limit - the maximum power transfer theorum says maximum power is transferred when energy in the flywheel and the mass are shared equally. Mass energy becomes 0.5 x m x v^2 and max height ...

View answer
Effects of Solar Shield on Electronics Enclosure
1 votes

Briefest start. Written from a hosp[ital bed just post operation :-) - better could follow if useful. Solar loading will be peak in hours around noon. Angles shift across year. Find your site 0n ...

View answer
What's a simple machine to lift and drop a 100 lbs weight repeatedly using an electric motor?
1 votes

100 lbm =~ 45 kgm. Wattage =~ kg x metres_vertical x 10 / time_seconds. So per metre of head, power = 450 Watts / seconds_to_lift. A battery electric drill (or even a mains drill) with a "drum" ...

View answer
How to calculate meters per pixel for a given camera?
Accepted answer
1 votes

Independent of what you are imaging, the ratio of object dimension to it's image dimension is a function of the lens focal length and the distance to the object. Knowing the sensor dimensions ...

View answer
Dc motors for controlling wheels of a wheelchair
1 votes

What speed and Power must the dc motor provide to move a wheelchair at above specifications. Wheel RPM = chair_speed / Wheel-diameter x 60 Motor speed = wheel speed/Gear_ratio. Motor power = ...

View answer
Plastic Injection Moulding a Piece with Undercuts
1 votes

I've worked on products designed by others which used injection moulding so while not an expert (and my terminology usage will be terrible) , do have a good feel for what may be attainable. I'd ...

View answer
Wind protection for solar installation
1 votes

Regulatory requirements will usually stipulate a mounting that will meet uplift conditions. Uplift is very approximately proportional to velocity-cubed normal to panel (eg under it facing up - so ...

View answer
What would be a practical way for removing thousands of padlocks from valuable bridge railings?
1 votes

The portable angle grinder that I saw them using on TV looked very effective. In the hands of a competent workman the risk of damage is minimal. With a cutting blade this is more a "geared metal saw" ...

View answer
Heat Loss per Linear Ft
Accepted answer
1 votes

I get 115.647 = 116 ie their answer. What you are doing wrong (in this problem and your other recent one) is going too fast and not visualising how the data given translates into the real world ...

View answer
Problem with Energy Transfer Rate Conversion
Accepted answer
1 votes

Your C to F conversion is correct for a different question. The Celsius and Fahrenheit scales have their zero points offset by a factor equal to 32 F degrees and this has to be allowed for when ...

View answer
How do products like the overheating Snapdragon CPU make it through quality control?
Accepted answer
1 votes

There is no good reason to think that Qualcomm's QC people did not detect the problem. It's what you do about it that is the problem. That there is or ever was a problem is denied by Qualcomm, some ...

View answer
How can I increase the CFM of my ceiling fan?
1 votes

Ceiling fan blades are usually rather crude airfoils - you won't find one in a NACA catalog :-). In many cases a certain amount of violence may be wrought on them without too much fear of disaster. ...

View answer
How much current is this phone drawing?
1 votes

If the meter is correctly connected between the charger and the phone then it will show the current that the phone as a whole is drawing. However, that does not mean that it necessarily shows the ...

View answer
Calculating kWh for different timestep
1 votes

In SI units the measure of "amount" of electrical energy is the Joule. Energy is a measure of "work done". Energy can be (and often is) expressed in terms of 'rate of doing work'. The rate at which ...

View answer
Upper bound for von Karman Vortex Street?
1 votes

I have a limited understanding of the subject, having investigated it for a specific project some while ago. That said - I understand that the general 'opinion' is that well below Re = 100,000 ...

View answer
Switching batteries from series to parallel - technical solution
1 votes

You have addressed many of the main points - it's really just "a matter of engineering". If you take 6V out from the top of the right hand battery and 12V from the 2nd contact down (12V output of ...

View answer
How to calculate the torque created by a rotating motor?
0 votes

The arrows on your diagram are intended as a visualisation aid but, in this instance, you are better off without them. Torque is (effectively) conserved. Applying a torque impulse to a body "in free ...

View answer
Control the rotation of multiple discs along the same axis
0 votes

A diagram would help. A sliced cylinder suggests parallel disks on a common shaft. "Top and bottom" suggests a vertical axle - is it? Inner ones may also mean vertical. How many slices? Are they ...

View answer
How was it possible to beat a soldier with a full plate armor?
0 votes

History for centuries past always depends on who writes it, and the Engineering behind the history is thus somewhat a matter of conjecture, but: The English Longbow and "Clothyard shaft" are said by ...

View answer
Measure the distance to a balsa wood strip with 1 mm accuracy
0 votes

If the balsa can be measured by contact based methods you can use an arm and roller or roller and plunger or various other displacement based means. If contact based means are not acceptable you ...

View answer
System identification on a system with constraints
0 votes

This partially an exploration of the question and partially a partial answer, but is not suited to the comment format. The following is "obvious enough" but provides two simple rules to allow you to ...

View answer
Mechanisms for moving dual blackboards
0 votes

Converted from a prior comment: Boards in such arrangements usually slide on pairs of tracks, one behind the other. Cords from one board go up over a top mounted pulley and down to the other board. ...

View answer
Percent (%) error between calculated gain and measured gain of FET amplifiers
Accepted answer
0 votes

"A simulation" is a series of calculations which are hidden and which you supply input parameters for. The simulation "models" the target device by embodying assumptions which may or may not be ...

View answer
How fast can Jansen's linkage driven walker go?
-1 votes

Short: Aren't they great ? :-) !!!! From below - " ... it is logical to expect them to typically act in the ethereal beautiful whimsical way that they do. ..." Observers "answer" - no claims ...

View answer
1 2
3