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Spent the day today experimenting with the recoil mechanism and the stepper.

The electronics and the code is working beautifully but when I tried it with a Nema 17 1.5A stepper motor I found that the stepper was not strong enough to turn the cam against the spring force. So I got a stronger stepper (2A) and today played around with it. Managed to get it to work with minimum spring tension and it seems to be repeatable.

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I am not sure about the RPM of the stepper as compared to the original DC motor though. What do you think? Is it too fast or too slow? I can make it go slower but I can't make it go faster as it will start losing steps.

Another thing that I did was to make the notch at the top of the cam a bit more pronounced. As it was, even with the slightest movement, the cam would come out of this notch. Used a 19mm slot drill (same diameter as the bearing) to fix this and it seems to work better.
Vince

Looks good to me Vince! Seems plenty quick enough on the firing stroke.

Looks like the return to battery on these Tiger shots is quite slow:



Adrian.

Thanks Phil and Adrian for that. So I guess I am quite close then.

Vince

Temporarily installed the muzzle brake to see if the recoil still works with the extra weight. Still working OK (fingers crossed). Having said that, I intend to change the stepper driver from an A4988 to a DRV8825. This is because the A4988 is working on the maximum current limit with this stepper motor whilst with the DRV8825 it won't be working at the maximum current limit.

Also today started work on the round hatches. I had all the bits and pieces for a while now but for one reason or another have been putting them off. I will be attempting to make "hybrid" hatches from Armortek and Armorpax parts and also Mark's brass hinges. Fingers crossed again!

I'm not sure if it would be of interest to anyone how I go about doing this.

Vince

Of course it is!

I've stole so many of your ideas Vince,anything is potentially usefully to me.




Glen.

OK, as there seems to be an interest at how I go about it, I will post my progress as I go along. I will be using a lathe and milling machine during these operations. I have been taking measurements and making plans for more than a week but as I said yesterday I have been putting it off as a lot of fiddly work will be involved.

I will be using the Armortek aluminium round hatch, Mark's brass hinges and Armorpax's white metal parts glued in. The aluminium round hatch will need to be eventually reprofiled but before doing that I will be locating all the white metal parts on the hatch. I thought I would start with the periscope and armoured cover.

Yesterday I filled in the existing milled slots in the hatch with JBweld and today I filed and sanded them flush.
The rectangular hole is too small for the periscope. So off to the mill to open up the hole to accept the periscope. I used a piece of paper between the mill table and the parallel and also between the parallel and the hatch to minimise the chance of the hatch slipping when being machined.
If you look close enough, I also drilled the two holes that locate the Armorpax periscope guard.
Removed the hatch from the mill and removed the rounded corners of the rectangular holes with a needle file. Still using the needle file, hand fitted the periscope.
Vince

Started work on the lower face of the hatch. Using the lathe, drilled a small blind hole in the centre of the hatch. Then using a divider marked and drilled the holes for the "thingies" that hold the locking arms.
Vince

Reduced a little the outside diameter of the hatch rings that fit to the hull roof.
Then cut a groove in the lower face of the hatch to accommodate the hatch ring.
Also cut a shallow recess in the lower face of the hatch to emulate the real thing.
With the same setup, flipped the hatch around and reduced the thickness of the hatch. One more operation remains on the hatches.
Vince

Finished the last operation on the Armortek hatches. This was to create the angled edge on the hatch (is bevel the correct term??). Had to rig up a jig to hold the hatch in the lathe chuck so that I could machine the angled edge.
There are some holes that need to be filled in with JBweld but I will be doing it at a later stage. Next operation is to work on Mark's brass hinges.

Vince

Looks fantastic. I will be adding Marks hinges as well - so I'm looking forward to what you do. Great stuff Vince.
Best regards,
Bob

Outstanding workmanship you certainly have an eye for detail, will you add the rubber seal to the hatches

Thanks Bob for having a look. I should start work on the hinges later on today.

Thanks Mark for the nice words. I thought about the rubber seal for a while but than decided that in my opinion I would be complicating life for little gain. Thought about using O rings or maybe thin rubber sheet cut to size. Then there's the problem of sourcing the material. I also think that with the rubber seal the hatch will sit too high unless one makes the groove deeper.

So at the moment I was thinking of painting the bottom face of the groove black to simulate the rubber seal.

Vince

Time to get my hands dirty on the brass hinges. I always get a bit nervous / apprehensive when working with castings. They are usually not easy to work-hold and if you ruin it you have to buy another one. I am happy to say that I spent more time worrying about it than actually making the holes for the brass pins.

I also asked Mark for any tips in doing the holes and he said to make sure they were vertical. So heeding Mark's advice, I started with the first part. Put it in the vice and using one of the brass pins that came with the kit in the drill chuck, I adjusted (eyeballed) the part to be as near to vertical as possible.
The places that need to be drilled have cast pilot holes, so I always chose the face with the best centred hole. Eyeballed with a drill the middle of the cast hole and then centre drilled it.
Next drilled and reamed 2.5mm the hole. There is actually no real need for reaming but as I had it I used it. It always gives me a nice sliding fit. Also, I won't be using the brass pins that came with the kit as they are imperial sized and I only have metric tooling.

The part I left for last was the hinge arm. I held it in the vice as shown below resting on a parallel. I was careful not to bend the arm in the vice.
Vince