Mk2 Lever frame musings

Discussions of the prototypes and how to model them. Show us how you do it.
JFS
Posts: 663
Joined: Wed Dec 16, 2009 3:47 pm

Re: Mk2 Lever frame musings

Postby JFS » Tue Dec 04, 2018 10:52 am

Just a bit more progress to show on the Leeds City Wellington frame. All that remains is to make and fit the locking bridles and cut the ports in the tappets...

Wellington Frameno locks.jpg


Meanwhile, the locking design is now up to version 5, though I feel this might just be THE one...

Here is the box diagram for anyone wanting to have a go...

Leeds Wellington Box Diagram v1_2 paper resize.jpg


Best wishes,

david_g
Posts: 3
Joined: Sun Nov 27, 2011 9:05 pm

Re: Mk2 Lever frame musings

Postby david_g » Wed Dec 26, 2018 11:15 am

Howard,

A few observations/questions about the lever frame and locking bar assembly:

Firstly both etches are a joy to build, go together easily and are quite addictive, having completed one section you just want to crack on with the next.

The lever frame even survived a couple of my ham fisted efforts, as a warning to others they were:

Be very careful forming the loop at the top of the catch rod, on one of mine I bent the half etched section once too often with the inevitable result that it snapped off. Repaired by forming a loop from some brass fret waste soldered both sides of the catch rod with the 0.6mm wire through the loop.
Soldering one of the catch boxes to the lever resulted in the catch soldering up solid. Frantic wiggling of the catch handle while applying the soldering iron to the catch box managed to free it off though it is still a little stiff. I'm wondering if working the catch handle with a little Brasso down the catch box might free it right off.

The instructions warn against both of these so my fault for not being careful enough.

Now the questions:

In the locking bar instructions p14 it says the initial target for the width of the crossheads should be 6.5mm; mine were nowhere near that to start with and after repeated measuring with vernier and steel rule I concluded this is a typo and should read 5.5mm. Am I correct? Forcing them into the slots in the cam plates requires a certain amount of faith and has left the finished sizes of my crossheads at around 5.4mm to prioduce a good sliding fit.
Similarly the cam plates have finished up around 8.75mm not 9.75mm as in the instructions p16 and didn't start that wide before I attacked them with a file. Another typo?
Finally the cam alignment jig instructions say use 1.4mm brass wire or tube to open the slots in the alignment jig. I've used 1.2mm tube which is very tight. Before I force 1.4mm in there I wanted to check this is correct.

A couple of photos of the state of play attached. I haven't fitted the drive pins to the levers or crossheads yet as the only thing I have to cut the piano wire is a 4.5" angle grinder which would be a little brutal and risky. I have gone for method 1 for the tappet assembly as the locking hasn't been worked out yet; that will be the next question after I have built another lever frame/locking assembly to extend the frame to 10 levers.

David

IMG_0186[1].JPG
IMG_0187[1].JPG

JFS
Posts: 663
Joined: Wed Dec 16, 2009 3:47 pm

Re: Mk2 Lever frame musings

Postby JFS » Wed Dec 26, 2018 10:58 pm

Hello Dave,

Firstly, many thanks indeed for the kind words re-the etches, and well done for making a great job of it judging by the photos. You might also be the first one to post a pic with the turned handles and very nice they look as well.

Now to your queries on the dimensions, regarding the 1.4 mm slots in the cam jigs, this is a simple mistake on my part as there is no such thing as 1.4mm brass wire and it is intended to be 1.2 mm.

Now, regarding the crossheads and cam plates, when I first read what you had written I was fairly sure you were wrong BUT when I checked you are quite right on both counts! What I cannot explain is how I made the mistake as a quick check on the drawing shows it as you have it. And I have only built about 35 of these things... My only excuse is that I never actually measure them as I have two pairs of spring bow calipers which I use... Maybe I should read my own instructions a bit more carefully.

Anyway, I will sort out the corrections to the notes and upload a revised version over the next few days. In the meantime, many thinks indeed for pointing these things out.

Best Wishes,

JFS
Posts: 663
Joined: Wed Dec 16, 2009 3:47 pm

Re: Mk2 Lever frame musings

Postby JFS » Wed Dec 26, 2018 11:10 pm

Just to confirm that I have uploaded a new version of the notes - Dave if you were able at your leisure, to re-download and confirm that I have done the necessary, I would be very grateful.

Best Wishes,

DougN
Posts: 874
Joined: Wed Sep 01, 2010 9:57 am

Re: Mk2 Lever frame musings

Postby DougN » Thu Dec 27, 2018 1:11 am

David, have to congratulate you on the lever frame it looks great and I hope works very well.

Howard the ability to go and create new instructions and up load is fantastic. This shows the ongoing ability of the society to continuously improve things. :thumb

I have put my suggestions for the Mark 1 on the other thread!
Doug
Still not doing enough modelling


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