Cyclic Force Trim Mod for Virpil VPC MongoosT-50CM2 Base

[CrashMeTwice]

Greeting Pilots!

Hope you are all doing well!
Today I would like to share with you the first part of my latest project in which I am adding a Force Trim function to the Virpil VPC MongoosT-50CM2 Base for my Helicopter cyclic. I have abandonment my previous mag lock idea and went to guide rails and steppers. I actually dreaded this project as it took such a huge amount of research on how this Force Trim system works in real Helis. I only have experience with the Robinson R22 and that was in the mid 80's. I am still working on it and until then I hope you enjoy the first part!

 

 

 

Edited October 25, 2022 by CrashMeTwice
duplicate removed

[Lucky13]

Very cool stuff! 

[edmuss]

Would this automatically return to the trimmed centre when deflected or does it just lock the stick in position when the force trim is released?

I'm actually in the process of developing a sprung mechanical lock that will hold my WH stick in any given position but release with a lever pull, combined with a switch onto a leo bodnar board it should act nicely.  No where near as well done as yours though

[CrashMeTwice]

4 hours ago, Lucky13 said:

Very cool stuff! 

Thank you!

3 hours ago, edmuss said:

Would this automatically return to the trimmed centre when deflected or does it just lock the stick in position when the force trim is released?

I'm actually in the process of developing a sprung mechanical lock that will hold my WH stick in any given position but release with a lever pull, combined with a switch onto a leo bodnar board it should act nicely.  No where near as well done as yours though

edmuss:
As an example, when the stick is moved forward and the lock button (momentary) pressed, this is now the new center position. The stick can move in any direction when pushed against a light spring load. When released the stick turns back via this spring load to the last set center position where it was locked. When the button is pressed again the lock disengages and the stick remains at that position but can now again moved moved freely without spring load to any new location.
The force trim allows via the 8 position hat switch on my Virpil grip to move the stick into any position via motors to a new center position and locks in that position when the hat switch is released.

I am also planning to integrate a "Home" button, which sets the stick to zero center in both axis. This will allow for easier calibration in the Virpil and DCS software.

At least that's the plan in my head

Edited October 28, 2022 by CrashMeTwice
duplicate reply

[edmuss]

That's awesome, effectively it's a force feedback cyclic

What I'm attempting will hold in one central position but won't give the ability to deflect the stick unless you pull the lever again. Well I could design something that would emulate it but it would complicate the design and I might have to call on the CNC machinist at work for a favour

[CrashMeTwice]

On 10/28/2022 at 2:53 AM, edmuss said:

That's awesome, effectively it's a force feedback cyclic

What I'm attempting will hold in one central position but won't give the ability to deflect the stick unless you pull the lever again. Well I could design something that would emulate it but it would complicate the design and I might have to call on the CNC machinist at work for a favour

Thank you!

Not being able to make corrections quickly without unlocking the stick may cost you the mission. I found myself many times in a bind when I used to fly with a simple mag lock (door lock magnet) design and forgetting that the stick was locked and when I realized it, it was usually to late. I have now completely abandoned it. To much effort and work (and frustration) for something which doesn't work the way I want to.

I have been working on the current design with rails and steppers for almost a year and find it a very good solution. A bit more expensive but you don't need a CNC to do it just some time. I know, it's easy for me to say but I have worked with basic tools before I had invested (a long time ago) into a Harbor Freight desktop mill and lathe and would never look back. It is fun to learn and will do any project you may encounter in the future. Food for brains?

Would love some more details on what your simpler design approach is.

[edmuss]

Ah if only I had the space for my own miller!

I have to make do with a vice and hand tools at home. I can use the pillar drill and lathes at work but we don't have a manual mill anymore, only a 2.5 axis CNC which I can't use, I can get bits made though.

I've got to spend a little more time in solidworks to finalise the design but the idea of still having some movement from the locked centered position world be nice if I can make it work; I have a couple of ideas to flesh out but will share them once a bit more developed.

The locking cam design I've decided on isn't going to be anywhere near the strength of a magnetic door lock so it will be perfectly feasible to push through it if required, just a case of muscle memory to remember to do it correctly.

[edmuss]

Sorry for the slight hijack!

I think I've got a workable mechanical solution for the deflection/return to trimmed centre

My warthog is setup with a 75mm extension, a custom base plate (it's a centre stick and needs to fit between my thighs) and a collar that clamps onto the handle fixing ring to facilitate fitting of things via M5 tapped holes.

 

 

The two rod mechanisms can be locked to a set length and work in unison to hold the stick on both axes, in one (trimmed) position.  The locks have the ability to deflect a small amount and should return the stick back to it's trimmed position.

Inside of the lock body is a shuttle (red) and cam (yellow) that locks onto the through rod.  The shuttle is sprung to a central position within the body (with an end cap on the open end - not modelled it yet) with a pair of compression springs that the through rod passes through.  The shuttle is locked to the through rod by the cam which has a compression spring concentric to the pull cable, when the cable is pulled the cam releases the rod and it's free to be set to a trimmed position.  With the sprung movement on the shuttle the stick should have approximately +/- 5° of movement whilst still holding trim and being able to return to centre.

The cables will be pulled via a bike brake lever mounted to the top of the extension, the lever will be vertical and sitting alongside the warthog pinky paddle.  The cable will be split 2-1 and independantly tensioned to ensure that both locks release at the same time

Nowhere near as nice as your all singing, all dancing design but hopefully should work quite nicely as a mechanical analogue

I've submitted the drawings for the body and shuttle to be machined in delrin, the through rod, cam and end plate I'll make but hand in aluminum.

[CrashMeTwice]

On 11/1/2022 at 7:18 AM, edmuss said:

Sorry for the slight hijack!

I think I've got a workable mechanical solution for the deflection/return to trimmed centre

My warthog is setup with a 75mm extension...

Very nice! Love to see it when you have it done! Delrin is an awesome material and really nice to work with.  I wish I had your skills in cad drawings!

[edmuss]

Ah I've spent the last 16 years using solidworks so this is simple modelling really. Have a look at my rudders build thread for more modelling and my attempts at manufacturing!

Once I get them made (and they work ) I'll likely start a thread in the input devices sub forum.

[CrashMeTwice]

Having some doubts with my approach...

Almost impossible on finding consistent resources on the Force Trim function as it seems every helicopter is a bit different as I get different answers in the forums or on the web. I would like to know on how it works from a piloting perspective in the Mi-8, Mi-24, or KA-50  models. I would appreciate if a real life pilot would find the time answering some of my below questions related to the force trim function.

Are the following statements correct:

(a) If I engage the Force Trim function the cyclic locks into that position and this is the new 0,0 position.

(b) I can still make corrections but the range is now limited and if I exceed that limit, Force Trim will disengage.

(c) If I move the cyclic from that new 0,0 position I will feel a "spring" load, returning the cyclic back to the locked position if I would let go of it.

If the range (b) is limited, by how much?

 

Thanks!

On 11/3/2022 at 8:32 PM, edmuss said:

Ah I've spent the last 16 years using solidworks so this is simple modelling really...

Very cool, looking forward to your post!

[edmuss]

From what I understand, your description matches the functionality, particularly in the mi24. I asked a very similar question not long ago and got video evidence of the trim operation in the mi24. I would make the assumption that the mi8 and ka50 is the same for the purposes of DCS

edit: I'm not sure if the motion from the force trim centre is reduced or not but it does seem to return to centre with a sprung force. The ka50 autopilot channels only have 20% authority once trimmed but I'm not sure if that is a physical limitation on the cyclic or a digital one by the autopilot.

Edited November 9, 2022 by edmuss

[CrashMeTwice]

14 hours ago, edmuss said:

From what I understand, your description matches the functionality, particularly in the mi24. I asked a very similar question not long ago and got video evidence of the trim operation in the mi24. I would make the assumption that the mi8 and ka50 is the same for the purposes of DCS

edit: I'm not sure if the motion from the force trim centre is reduced or not but it does seem to return to centre with a sprung force. The ka50 autopilot channels only have 20% authority once trimmed but I'm not sure if that is a physical limitation on the cyclic or a digital one by the autopilot.

 

Wow, that was an awesome video! Thanks for your reply, it makes so much sense now and is a great help for my project. I have several options and I wasn't sure which type of trim return I wanted to use. I am flying mostly the Mi-24 (feels more refined) but I do like the Mi-8 and the KA-50 too. I have difficulty implementing full range trim and may have to build my own dampers as all the steering stabilizers I wanted to use are just to large in diameter to fit within my small box between my legs while still having room to use the rudders. This project is likely the most complex one I have taken on thus far.

Anyway, Thanks for all the input!

[edmuss]

The dampers I picked up for my stick (which proved to be ultimately a little heavy for the usage) aren't all that big and could be packaged into the side on a stick extension pretty easily.

The damper force could be changed by drilling out of piston ports, they're fully serviceable so no issue to dismantle them. I played around with different oil weights but didn't get so far as drilling the pistons. I'm going to reutilise them on the rudder pedals and the collective I'm planning.

They cost £12 each on eBay and whilst cheap they work really well for what they are. I modelled them up in solidworks (as per attached image), the body is 100mm long and free stroke is about 55-60mm, overall length is about 200mm.

[CrashMeTwice]

I purchased some Motorcycle Steering Stabilizers on Ali for 25 bucks each which are fully adjustable and rebuildable. I have used them with light weight Lucas fork oil but they don't work for my new project as I require a lot more of stroke. For rudders they are great though! I am now looking at dampers which have 120mm stroke and they may be just long enough to work. However there are a bit pricey at 45 bucks each. I thought maybe I could make my own from some Lift gate dampers I have laying around in the garage from my old truck which was scrapped some time ago.
About drilling out the piston, I have tried that and it made the damper very noisy and "sticky" but it may turn out ok on your model. Mine became unusable until I fixed it by re-closing the hole with a set screw.

 

That's the one I am thinking about.

Edited November 10, 2022 by CrashMeTwice

[CrashMeTwice]

Sorry, a bit off-topic!
Disaster has struck in my workshop.

And there I was happily working on the Force Trim Mod getting ready to cut a aluminum rod when this happened!
The bench vise decided to throw me a curve ball. Just broke so I am thinking what?
Couldn't believe it? I had this for over a decade and now it quits on me from one minute to the next!
How could I finish the next part of my project is my next thought and the answer is, not today!
I will be spending some time on figuring out what's a good vise will cost me and which one will not leave me hanging like this one.

There will be a bit of a gap towards the next update on this project. Hopefully I get a good deal on a new one.

 

 

[edmuss]

I have one of the old welders vices from work, it's a record and so incredibly heavy and overbuilt, got to be about 60kg!

I'd ask around local engineering shops to see if they have any old vices spare, alternatively eBay for a ropey old one and spend some time cleaning it up

[CrashMeTwice]

Thanks for the input.  Got a cyber week discount on a a open box Capri Tools 6" forged vise which was a super cool deal. Should have it by Wednesday. Finally my project can get on it's way again.

[CrashMeTwice]

Greeting Pilots!

Just finished editing and uploading part 2 of my force trim mod. So far I have build the base plate and rails, I also have created the bridge plates for the rail blocks. I have drilled NEMA 17 mounting holes on the bridge plates and installed the Modulus 1 Gear Rack with a aluminum base on which the 10 tooth pinions run to move the block assembly along the rails. I noticed that I needed a bit more room between the rail blocks and that meant to take off a bit of material from the blocks. I have mounted my old Nema 17 steppers for now (Replace them later on with Moose's steppers (Higher quality, Dual shaft, more torque). I also created a stick extension from 6061 aluminum which required a bit of machining and filing. I have removed the cam bearing which I no longer need and using the existing hole of it to mount the extension. In a matter of fact I will not  re-use the bearings, cams, or the cam arms of the original setup. Still a work in progress
 

You all have a nice holiday season!

 

[Lucky13]

Awesome work!

[edmuss]

Everyone needs fancy elongated pockets!

Good work, I miss not having access to a miller or the time to use it

[CrashMeTwice]

55 minutes ago, edmuss said:

Everyone needs fancy elongated pockets!

Good work, I miss not having access to a miller or the time to use it

Thank you! Yes, fancy pockets are the most important thing on any project LOL

Time, well, when I was young, I hadn't time to tie my laces but now I'm in my 60th and retired, I have so much of it that I had to find something to do or ending up as a permanent chauffeur for the wife's shopping trips. This is one of the reasons I choose to restart my simming hobby, of course it was not because nobody else in the family knows a thing about it and I will miss very much all the concerns and advise on everything and anything I do. Trust me when I say that eventually you will get the time, be it sooner or later.

Yes, the mill, I couldn't live without it for sure. It has been my most versatile tool in the shop. Just got an extended bed for it too with 30% extended travel in both axis. This was an early x-mas present to myself!
Best thing about it was that the wife was out shopping while the UPS guy huffing and puffing dragged it in. That said, I may be able to buy me another late "first and only" x-mas present

Thanks so much for your comment! Made my day!

[edmuss]

My dad trained me up on the lathe at around 12 years old, he let me loose on the miller around 15.  I had all the time in the world and having a workshop at home was amazing, I spent hours on end making aluminium swarfe and broken milling cutters

I mostly made bicycle parts and the miller was so worn out with about 1/2" backlash in the lead screws you had to lock the gib down solid so that it was almost impossible to traverse the bed!  Character building, I think that's what my dad called it  

I'm 20 years off retirement currently (although the state the country over here it's going it's probably going to be 30) and I can hopefully have time and space to tinker.

[CrashMeTwice]

23 minutes ago, edmuss said:

My dad trained me up on the lathe at around 12 years old, he let me loose on the miller around 15.  I had all the time in the world and having a workshop at home was amazing, I spent hours on end making aluminium swarfe and broken milling cutters

I mostly made bicycle parts and the miller was so worn out with about 1/2" backlash in the lead screws you had to lock the gib down solid so that it was almost impossible to traverse the bed!  Character building, I think that's what my dad called it  

I'm 20 years off retirement currently (although the state the country over here it's going it's probably going to be 30) and I can hopefully have time and space to tinker.

I am afraid you are not alone in your backlash experiences. Why do you think I bought a new table/bed for the mill...

LOL Character building

[CrashMeTwice]

Greeting Pilots!

Just uploaded part 3 of my force trim mod.
I am working currently on the frame and chassis for the Force Trim Mod. I also have installed side mounted guide rails onto the frame posts.

Please check it out.