How to make realistic WWII era trim wheels?

[tapi]

To achieve this goal look first to this short vid of how trims for F4U looks and feels like in action (see time 0:55):

 

 

So we need:

1. Robust construction to allow pilot's hand rest on in, i.e. main shaft (axis) for the wheel should be from metal and should have at least 6-8 mm in diameter and the shaft should be attached to at least two holds. Some small bearings should be used (e.g. bearings for RC cars?).

2. The wheels should have some resistance (stiffness) to avoid moving it by accidental touch (application of some sort of friction device attached to the shaft would be necessary)

3. The wheels should be precise, i.e. NOT 1:1 between Wheel and Pot. Instead, there should be some sort of gear so that large movement of the wheel causes only small movement of pot axis.

 

Add 3) To explain what I mean if I speak about the gear see the attachments - pictures of my home-made box of 6 levers. I needed to achieve exactly the opposite goal i.e. small movement of the lever should cause large movement of the pot axis. But the principle is the same.

 

Note: my construction is not perfect - main drawback is too small shaft (axis) diameter (only 4 mm), and small resistance so that construction is not as robust as it should be.

 

My intention is a robust trim box with all three trim wheels that can be placed on the side of my chair. Something like this (but with above-stated parameters):

 

 

Any hints and comments welcomed.

Edited May 11, 2020 by tapi

[tapi]

There is an example of what I DO NOT WANT to achieve, i.e. trim wheels attached directly to pots.

https://a2asimulations.com/forum/viewtopic.php?t=50390

 

See especially this image: https://s12.photobucket.com/user/pizano1/media/DSCF2872%2520Medium_zpsgkmeutqv.jpg.html

Edited May 11, 2020 by tapi

[tapi]

This one looks more robust but still 1:1 gear

 

Edited May 11, 2020 by tapi

[tapi]

Here are the vids with home-made geared trim wheel:

 

He use 3:1 gear ratio and ball bearings for wheel shaft.

 

Edited May 11, 2020 by tapi

[tapi]

Another home-made solution of geared Trim wheel:

 

[tapi]

Max range of trim wheels in the sim:

 

Spitfire

ELEVATOR Trim: 2 full turns (720°)

RUDDER Trim: 1 full turn (360°)

 

P-51 MUSTANG

ELEVATOR Trim: 1 and 3/4 turn (630°)

RUDDER Trim: 2 full turns (720°)

AILERON Trim: 2 full turns (720°)

 

Conclusion: we need trim wheels capable of 2 full turns (720°)

[tapi]

How to calculate diameters of both tooth wheels:

 

L = 2 * R * sin(A/2)

 

L = circumference of the wedge

A = angle of the wedge

R = radius of the wheel

D = diameter of the wheel (D = 2 * R)

 

Big wheel on the POT:

A1 = 270° (standard pot turns 3/4 of the full turn)

D1 = ?

 

Small wheel on the TRIM:

A2 = 720° (2 full turns)

D2 = ?

 

Here are examples of calculated combinations:

 

D1 = 30 mm

D2 = 11 mm

 

D1 = 40 mm

D2 = 15 mm

 

D1 = 50 mm

D2 = 19 mm

 

D1 = 60 mm

D2 = 22 mm

Edited May 12, 2020 by tapi

[tapi]

Alternative mechanic solution:

Instead of the shaft for the wheel a long screw can be used.

The trim wheel should be firmly fastened to the screw and so turning the wheel cause screw in / screw out the long screw. Then some optoelectronic solution can be used to measure the distance of the screw movement.

The length of the movement should be max 10-15 mm and is dependent on the up-grade of the screw-thread.

 

Advantage of this solution: very robust construction

Disadvantage of this solution: movement of the wheel (in case of the ELEVATOR trim there would be horizontal movement of the wheel while turning)

Edited May 12, 2020 by tapi

[tapi]

Flight Velocity Trim wheel

https://flightvelocity.com/products/flight-velocity-trim-wheel

 

Review on YT:

 

Not sure how many degrees or turns this wheel is capable of...

But I like this click-click sound while turning the wheel :)

 

Edited May 12, 2020 by tapi

[tapi]

3D printed trim wheel - looks interesting

[tapi]

Trim wheel from CD :)

 

Seems to have long-range of the turns

 

[tapi]

Nice geared trim wheel for C172

Range: from -2,25 to + 2,25 turns, i.e. 4,5 turns

[tapi]

Saitek Trim Wheel tested on DCS P-51

[tapi]

Good quality metal gears from China:

https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20200520225256&SearchText=metal+gear+

[Svsmokey]

This thread would be better-placed in the home cockpit builders section of the input/output sub-forum

[tapi]

I have no problem with moving the thread. But I think that can do only admin, right?

[shu77]

Heres some input for you on the saitek wheel from the marketing blurb:

Fly using the actual trim wheel found in Cessna 172/182 aircraft: Saitek's Pro Flight Cessna Trim Wheel. Rotating through 9 full revolutions to recreate the genuine Cessna control movement, extremely accurate pitch control is at your fingertips. A unique 2-position desk clamp keeps your Trim Wheel securely fixed no matter how extreme the flying conditions.

[tapi]

Interesting - 9 full revolutions. Did not know the Cessna's trim has so many revs.

[SDPG_GVL224]

[tapi]

Yes, good idea from GVL. Vitalij used pots for 3x360 degrees. The range of this trim is good. Point 3 from the initial specification in the first post is OK. But still there is a very low resistance of the wheels so the pilot must be very careful not to unintentionally touch especially the big wheel. So the points 1 and 2 from the first post are still not accomplished.

[Sokol1_br]

Alternative mechanic solution:

Instead of the shaft for the wheel a long screw can be used.

The trim wheel should be firmly fastened to the screw and so turning the wheel cause screw in / screw out the long screw.

 

Could be fun "reinvent the wheel" in that way, :) but geared potmer already exist, the called "multi turn potentiometer" with 3, 5 and 10 turns.

 

https://potentiometers.com/select_multi.cfm

[tapi]

Yes, I know about multi-turn pots, but some gear would be necessary anyway because of the point 1) from the first post, i.e. robust construction cannot be based on a weak pot axis. There is a need for much stronger axis for trim wheel. So, with multi-turn pots I should use 1:1 gear anyway. So why not use the gear ratio that gives me exactly 2 turns (to comply with most common range of warbirds trims) instead?

[tapi]

Looks like REPLIKA Gear is going to produce high quality trim boxes:

https://forums.eagle.ru/topic/236987-wwii-replika-throttles/?do=findComment&comment=4494205

 

Quote

Trim wheels will be multi-turn. Replica ones as many turns as the real things. A generic one will have an average of those, 2-turn, 5-turn whatever the average will be. And movement damping just like my base and my throttle levers for fluid motion and stop.

https://forum.il2sturmovik.com/topic/62313-replika-gear/?do=findComment&comment=1026963

 

 

Edited December 4, 2020 by tapi

[tapi]

Well, my project of building realistic trim wheel is finished and I can say it is a success

Basically a cheap solution with parts mainly from chinesse e-shop aliexpress.com

 

Solution: two metal axis with diameter 8 mm, small ball bearings, belt pulleys 60teeth and 20teeth for 3D printer, and 100kOhm pot with metal axis (diameter 4 mm)

 

More photos as well as list of links for parts see my blog post here: http://www.warbirds-blog.cz/?p=7257 

(the text of my BLOG is in czech language but I think the photos tell most of the story 

 

 

Conclusion: This solution fulfill all three points from the first post of this thread.

 

 

 

Edited December 15, 2020 by tapi