English Measurement Rounding Tool

This simple calculator takes a measurement and rounds it to nearest standard English units.

I have used this when building my CAD designs. My designs in CAD have arbitrary, messy measurements (i.e. 1.734854" vs. 1 3/4"), and in order to measure and mark my raw materials I need to convert it to standard English units. I use this calculator for the conversion, and to determine whether the rounding is sufficiently accurate. My rule of thumb is to keep the difference between the exact and rounded measurements less than 10 thousandths of an inch. Depending on the precision requirements, more or less difference can be tolerated.



Measurement:
Precision: 1/64 1/32 1/16 1/8

Rounded Measurement:
Difference:

Potential Flow Playground: Puff

Here is a little JavaScript program I wrote that allows one to play with potential flow by inserting sources in a wind tunnel. Potential flow is an idealized flow characterized by irrotationality. The particular form used here has the added characterizations of being inviscid and incompressible, and satisfies Laplace's Equation for a velocity 'potential':

The velocities are recovered by:

Second-order-accurate finite differencing schemes are used to recover the velocities.

I will continuously be working on this, so this is by no means the final version. Currently I aim to bring the following:
-Doublets
-Vortices
-Making it into a game

It is colored by potential. Click on it!


Discrete Resolution:

Pixel Dimensions:

Specifications of the Turnigy TR-111

I recently bought two 11.5 HP gas engines from Hobby King. They are made by Turnigy and have the designation TR-111.



Surprisingly, there is no way to get any information other than on the product page. There is not even a mention of it on the Turnigy website. So, here I post information that I have gleaned from inspecting the engine myself. I planned to use these engines together to the power the same drive shaft to get about 23 HP. I picked the TR-111 engine because they were relatively cheap, lightweight (NW of 2.5 kg each), and satisfied my power target of over 20 HP.

To see it in action, check out the video from 'redsjcman' (who also has a review on the HobbyKing product page):



I do not have a video of my own yet, but hopefully I will soon.

Now, let us move on to the specifications.

First, the general specifications listed on the box:

MODEL: TR-111
DISPLACEMENT: 111.27 cc
BORE AND STROKE: 45 mm * 35 mm * 2
IGNITION: Electronic Auto Advance Ignition
SPARK PLUGS: CM-6
POWER RATING: 11.5 HP
PROPELLER: 26*12 27*10
SPEED RANGE: 1400 PPM - 7000 RPM
OIL: 25-40: 1 MIX (the octane number should be 93 or higher : lubrication Type of 2-cycle oil)
NW: 2.5 kg

I made measurements using this dial caliper from Harbor Freight. I use three significant digits.

Abbreviations:
ID = Inside Diameter
OD = Outside Diameter

CONTENTS:

4 x (Standoff Spacer, Bolt and Washer)

Standoff Spacer Dimensions:
-0.789" (20.0 mm) height (distance parallel to axis of symmetry)
-0.615" (15.6 mm) small OD
-0.782" (19.9 mm) large OD
-0.236" (5.99 mm) bore
Bolt Dimensions:
-0.188" (4.78 mm) unthreaded diameter
-0.328" (8.33 mm) head diameter
-0.161" (4.09 mm) minimum hex socket diameter (for 4 mm Allen / Hex key)
Washer Dimensions:
-0.205" (5.21 mm) ID
-0.471" (12.0 mm) OD
-0.041" (1.04 mm) thickness

2 x (Muffler, Gasket, and Pair of Bolts):

Muffler Dimensions:
-1.956" (49.7 mm) can diameter

-4.046" (103 mm) can length

-0.984" (25.0 mm) chimney diameter

-0.045" (1.143 mm) chimney thickness

-~3.75" (95.3 mm) chimney length

-0.384" (9.75 mm) hex key passage hole diameter

-0.591" (15.0 mm) mount rectangle height

-1.03" (26.2 mm) mount rectangle width

-0.222" (5.64 mm) mount bolt hole diameter

Bolt Dimensions:

-0.192" (4.88 mm) threaded diameter

-0.330" (8.38 mm) head diameter

-0.160" (4.06 mm) minimum hex socket diameter

Gasket Dimensions:

-0.864" (21.9 mm) overall height

-2.04" (51.8 mm) overall width

Engine:

Overall Dimensions (stripped down;unequipped with mounting hardware, ignition system, etc.):
(Please note these dimensions were not taken with a caliper, but with a ruler)
-6 11/64" length (excluding small shaft)
-10 5/32" width
-6 3/4" height

Engine Mounting Plate Dimensions:
-2.519" minimum distance between holes on shorter side.
-3.049" maximum distance between holes on shorter side.
By taking the average of the last two measurements, we can infer the hole center distance.
-2.784" (70.7 mm) center distance between holes on shorter side.
-3.435" maximum distance between holes on longer side.
-2.905" minimum distance between holes on longer side.
By taking the average of the last two measurements, we can infer the hole center distance.
-3.17" (80.5 mm) center distance between holes on the longer side.

Engine Small Shaft Dimensions:
-0.391" (9.93 mm) diameter
-1.571" (39.9 mm) length
-0.173" (4.39 mm) threaded hole inner diameter

Propeller Mounting Hardware:
6 x (Bolt, Washer, Split Lock Washer)
Cap

Bolt Dimensions:
-0.191" (4.85 mm) unthreaded diameter
-0.325" (8.26 mm) head diameter
-0.162" (4.11 mm) hex socket minimum diameter
Split Lock Washer Dimensions:
-0.217" (5.51 mm) ID
-0.324" (8.23 mm) OD
-0.053" (1.35 mm) thickness
Washer Dimensions:
-0.206" (5.23 mm) ID
-0.393" (9.98 mm) OD
-0.019" (0.483 mm) thickness
Cap Dimensions:
-1.676" (42.6 mm) OD
-0.398" (10.1 mm) bore
-0.153" (3.89 mm) thickness
-0.206" (5.23 mm) bolt hole diameter
-0.919" inner bolt circle diameter
-1.328" outer bolt circle diameter
From the average of the previous two, the bolt circle diameter can be inferred.
-1.1235" (28.5 mm) bolt circle diameter

From installed mounting spacer to shaft tip, the total length of the engine would be about 8.53".

Ignition System:

Text on the metal box:
CDI Rcexl
Automatic advancing angle ignition
for gas engines      Model:A-02
ELECTRONIC IGNITION
Voltage-Range: DC 4.8V/8.4V
Temperature Range: -40 degrees C / +60 degrees C

If you have any suggestions or requests, make a comment below.