Arbor press bending brake press

At first glance my arbor press bending brake press modification might not seem amateur radio related but in fact the first job for it will be element mounting plate support brackets for a 10m moxon.

As a hobbyist we have probably all bent sheet metal in a vice tapping with bits of wood etc but it’s always a bit of a poor job at the end, certainly when I do it anyway! But some time ago I got hold of a small vice based bending set like this:
vice press brake setAt the time I didn’t actually have a vice only having a drill press vice but the jaws on that don’t open wide enough to take these so it sat around doing nothing for a while.
I did then decide I needed a vice for this and other jobs so got myself one and did some small brackets for my TMF-3 based DXcommander style vertical portable antenna.
brake press fitted into viceBut in making these simple L shaped brackets I noticed a couple of things. It’s really hard to make a fold the exact angle you want at all and even harder to make more than one the same! Also, as my ‘workshop’ is usually the bench in the garden so my vice is packed away when not in use and not bolted down to a bench like most I have to clamp it down to stop all the weight at the front tipping it over. Additionally there is very little ‘throat’ so the longest flange you can make is about 3 inches, the distance above from the bending V to the top of the sliding body part. So I decided I would utilise my arbor press.

The first hurdle was the shape of the bending vee parts which are designed for the vice jaws with no consideration whatsoever given for someone wanting to use an arbor press! How very dare they!

Once I drew up the arbor press ram and the punch of the bending set I came up with the idea of bolting a thick steel bar to the the ram then the bending punch would stick to that. Initially I thought I would drill up into the end of the ram as I see several people do to mod their arbor press for tooling but I didn’t feel a single hole would be good enough and there wasn’t much space there for a pair of holes. Also I decided I wanted to keep the press face flat as I use it for things like pressing in The YBB Washer so I went for a bolt through with brackets:
Ram and bending punch assemblyI then decided I wasn’t happy relying only on the magnets to hold it in place so I decided to drill through, tap the body of the vee punch and screw it to the steel bar. To do this and ensure everything was well lined up I decided I needed to clamp it all up and drill them together. The vice came out and also the speed clamp to stop it falling over! I used the vice to press the locating ‘ears’ to the side of the steel bar and G clamps to press the magnetised face to the bottom of the steel bar, drilled pilot into both, tap drill into both, clearance hole into bar, tapped then countersunk the screw hole all in the vice.
fixing vee punch to steel bar

tapping the vee punch
ram assembly finished
Next was the vee side of things to sort out. Initially I planned to used the metal half from the kit but it meant making something to support the odd shape and screw those together. Much easier was just to 3D print a new vee part.

I happened to have a piece of 8mm thick steel pretty much the perfect size for the bed of the arbor press, one of those “one day this will be useful” keepsakes. This would make a strong base for the bending vee. I wanted a guide fence as well to make the bends perpendicular to the side of the metal. This is a different arrangement from the CNC brake presses at work (yes-I actually work for a sheet metal company with a full manufacturing facility but I rarely ever go in as I work from home) where you have a variable backstop that sets the bend width and you push the metal against that and make your bend. Here I will be relying on marked bend lines and the fence to keep it square. I wanted the fence movable so that for narrower metal than the width of the punch and vee I could move the fence so the metal centre was below the ram centre.
Additionally I wanted the fence to also act as a guide to ensure the punch and ram came down centrally in the vee as the arbor press is not a precision machine.
bending vee and fence
Above is the 3D design of the arrangement. As few sets of holes in the steel plate as possible (as it is there is a total 176mm depth of 3mm holes in steel!) and sets of holes on smaller pitch on the aluminium angle fence. And the gap between the two halves a little wider than the punch.
It turned out that my handy plate was not square. It was clearly a length of 150mm wide steel bar chomped into the length as the sides were parallel but the ends were not. This meant accurate marking of sets of holes for the fence and vee was very hard with a square. Instead I printed a drawing 1:1 scale with cross points on all the holes and taped that to the steel plate and used that to punch to. I have successfully used the same method to make the hub plates on my lightweight 20m moxon which you can see would have been a nightmare to draw out!
So here is the real thing after drilling:
bending vee and fence madeThe bending vee is printed in PETG which should be more than strong enough, I have seen people bending thick steel with PLA bending sets and I have also mounted them with overly long M3 screws that are just a mm or so short of the top face.

Initially my plan was to drill and tap some fixing holes into the bed of the arbor press to mount this plate but I realised the shape would not allow me to get a drill in except from below. So I changed my mind and have gone for a different approach. I recently bought some magnets to make a digital DRO for the mini lathe as seen here on my friend’s youtube. This style of magnet focuses the field and are quite strong I decided they would make good magnetic feet. A word of warning, don’t be too enthusiastic tightening them up, you can see I have cracked one! The actual down force from the ram will be taken by the steel outer shell of the magnet so I am not worried about further damage.
baseplate with magnetic feetWhen fitting the baseplate to the arbor press I will insert the vee into the point of the punch then lower the ram until the baseplate sticks to the arbor press base so that I know it is in the correct spot.

We’re almost there, just one more ‘issue’ to solve. The very first parts I want to make have four folds that need to be the same so the two ends are in the same plane and that plane is parallel to the centre part as so:
first bent part to make
No way am I going to be able to guess this. Back to the 3D drawing board for the solution.

The bend I need for this part is only 15° which is nothing for the brake press. Putting the bracket into the brake press assembly shows the minimal amount of movement required. My solution was simple and removed the need for any complex depth stop arrangements. A simple slide in depth stop in the V will make a repeatable mechanical stop. I allowed a very small gap for spring back but these small aluminium parts are not springing back much:
bending depth stop 3D design
A set of these depth stops will give me various angles, and a tiny one will give me the 90° bend as I made the vee block angle 80° to allow for spring back. Here is my first set. I missed a trick here as I have a Bambu Lab P1S with AMS now and could have printed the numbers in another colour but marker pen works..
bending depth stop set
So now I am set and ready to bend up my brackets. (Almost- I need to come up with an improved clamping system on my hand guillotine to stop the sheet moving…)

Here is a quick first go. You can see from this that unlike the vice based version at the start we have almost unlimited length of material we can bend across:

And here are the first test bends. The 90° is over bent as I hadn’t made the stop for that yet. The 7.5 (the numbers are the height of the triangle in mm) turned out spot on for 30° bends I needed for one bracket and 8.5 almost for the 15° bends. I made an 8.6mm one which is shown in the earlier 3D image which gave me my 15° bends nicely.
set of test bends

Mini lathe cross slide modification

You may wonder what a mini lathe cross slide modification has to do with Amateur Radio but it is a tool I use a lot for radio gear. Mostly for the plastic bearing rings on my coax loop free guy rings ( https://g1ybb.uk/g1ybb-coax-loop-free-guy-rings/ ) but also for other little items like the YBB Washer ( https://g1ybb.uk/the-ybb-washer/ ) so very closely related to my radio activities.

My lathe is a cheap Warco mini lathe that I bought from an old friend G3LZM (now SK) and it sat unused for a LONG time. But now it sees more action and as a good friend of mine recently bought the Warco super mini lathe and has corrected some of the cost saving shortcuts I am trailing along adding a few to mine. So this one deals with the cross slide, or to be precise, the lead screw.

mini lathe cross slide exploded drawing

As seen in the exploded view above the lead screw (item 5) has a shoulder on it that sits in a machined recess in the cross slide boss (item 4) and it trapped up against the main body of the carriage (item 52). There is no bearing at all and the boss is aluminium. You can see this in my photo below:

boss and lead screw
So my friend decided to solve this by adding a thrust washer either side.
These are the thrust washers:
thrust washers
These are too large in outer diameter to be used with the original boss as the two M4 fixing holes are too close together. So a new boss is required. My friend made a 3D printed test piece then machined a new aluminium one but I am just going to print one from PETG which is more than strong enough for this application.

My friend sent me the 3D model he did and I tweaked it to suit my intent and lathe. Here you can see the 3D printed boss as transparent and the 2 thrust washers either side of the lead screw shoulder in a larger recess in the boss:
cross slide 3D modelTo fit this I needed to drill and tap two new fixing holes in the carriage. I didn’t want to take it all apart to drill so decided to drill in place. But it’s really hard (for me!) to hold a drill (and then a tap) square. So the 3D printer said “Hold my beer, I got this for you”
I drew up drill jigs. These have a boss that goes in the lead screw hole in the carriage with a close fit and two 4.0mm holes for the existing fixings. The two 2.0mm holes for the pilot drill. I made a 2nd jig with 3.0mm holes for the next size up drill in case the first one was worn making the initial hole. These were in PETG and actually showed next to zero wear.
drill jig

Here is a test fit of the drill jig (excuse dodgy throat-bad cold):

And here in use:
drill jig in use
I decided to use it to guide the tap in straight as well which worked very well.
tapping with drill jig
I was then able to do the test fitting. There were a couple of issues. The pocket for the thrust bearing was a little too shallow so when the boss was tightened to the carriage they were under pressure and not running freely. The bore in the boss was a little snug on the lead screw shaft but the one thing that made it scrap was the boss was a bit too long for the graduations wheel. I didn’t have it with me at the computer (doh!) so I needed a tweak:

Back home and after a few minutes in Solidworks and an hour or so on the (new faster Bambu Lab P1S) printer and a new version is ready:

Back to the lathe and install it and seems to work a treat. I literally can’t detect any backlash at all really, surprisingly. That’ll do for me!
Apologies for my dodgy throat again in this one from a bad cold. A point of note is the graduation dial is now in mm as the lead screw is metric yet the lathe comes supplied with a dial in thou.

 

 

 

The YBB Wire Winder system for radials

This page describes the YBB Wire Winder system for radials for amateur radio vertical antennas and why I have come up with this design to make winding up vertical antenna radial wires easy.

I’m in the process of using my 50 foot fibreglass push up mast as a multiband vertical antenna as often referred to these days as a DXCommander. The build of that is detailed here:
https://g1ybb.uk/tmf-3-based-dxcommander-style-vertical-portable-antenna/

But one thing I have already discovered in various tests is the wire radials for the ground plane are a complete pain in the butt to deploy and untangle. If you do not spend some time at pack up taming the wires you are surely going to regret it next time!

My radials are in bunches of 6 soldered into one ring terminal per 6. Six wires really love building birds nests for some reason. Currently I am coiling up each wire and securing it with tape, then putting the set of six into a bag to isolate them from all others. This works but is very time consuming and will fail when raining as the tape won’t stick. Here is one set:
6 radials coiled up
As I have several sets of radials of differing lengths I needed to come up with a better solution to make it faster and easier. After some pondering I have come up with The YBB Wire Winder System for radials.

In previous builds I have made winding spools for wire dipoles such as seen on this page:
https://g1ybb.uk/3d-printed-wire-winding-spool-for-sota-hf-dipole/
which is OK and works for the two legs of a dipole but would be tedious for 20 or more radials for the vertical antenna. So I decided something like that but operated mechanically by my battery screwdriver could be the answer. I have some extra long screwdriver bits like these:
extra-long-screwdriver-bitsMine are not quite as long but they have 7cm of hex shaft available, plenty to drive my spools.

The spools of course would be 3D printed to my design so I set about designing. A consideration when designing parts for 3D printing must be made to make it easy to actually print. My initial concept is shown here:
YBB Wire Winder System draftThere are seven spools, 6 for wire and one to contain the common terminal. I’d already decided the start point of winding needed to be the terminal as winding from the other end would require perfect winding and perfect length to all end up at that common point. But looking at this image above it’s instantly clear printing this is going to need supports, which is material to stop the extruded plastic falling down if nothing is below it. Here the orientation shown is probably the best way to try to print it but each of the 7 spool cores will need support as they are in space. The larger diameter side cheeks would actually print OK as shown as each layer will slightly overlap the previous one to start building the circles.

But I hate prints with supports, usually leaves a mess when you take them off. Plus I wasn’t sure exactly how big the spools needed to be. So the answer was to make it modular which mean I could also print one test spool at a time.
modular system single spoolThe modular spool above can be printed in that orientation perfectly with no supports required at all.

Then it was a case of making a set of parts with differing features depending on their position in the stack.
spool2 of modular systemAbove is shown spool2. this has the features of the wire slot to pass a single wire through to the outermost spool (spool1) and a wire retention feature. And some filament saving and drainage holes. And two 3mm holes for M3 studding to assemble the whole assembly.

The above animation shows the assembly. If you pause at the start you will be able to see more details and features. You can see the narrow centre section with a peg for the ring terminal and the bottom of the wire slots have a cutout at the core for 3 wires, then 2 wires to sit in. The right hand side spool is made from two half height spools back to back so all can be printed easily as described above.

This drawing shows the different parts. Only spool3 is used twice here. This could be a 4 wire assembly just as easily, by omitting both spool3 instances.
YBB Wire Winder System drawingHere is a PDF of the same drawing for better detail:
https://g1ybb.uk/docs/YBB%20Wire%20Winder%20system.PDF

All very good but does the YBB Wire Winder system actually work?
Time to test it out.

After manually deploying the radials in the garden, here is the packing away sequence. I cock it up a bit at the start but it was my 1st go!

You’ll notice I have some M8 nuts tied on the end of each radial to give it a little weight when setting them out in the fan arrangement. I’m brushing the edges of the spools to help keep the wires spooling in the correct partition.

And here we have the deployment:

You’ll notice in deployment once there was about 3 feet on the ground it all un-spooled very well. This will save me a massive about of messing around at setup and tear down!

Some practical notes…

YBB Wire Winder system loaded up
The above pic shows the YBB Wire Winder system loaded up with 6 radials that are each 5 metres long. The wire I have used is 2 x 0.5mm² red and black speaker wire split into two wires as it was the most cost effective way of getting the many metres of wire required. You can see there is plenty of capacity left but I also have longer radials that I will see if they will fit the same size spool. If not, for greater capacity it is probably easier to to increase the width between the spool cheeks.
Update: I have just wound a 10m length of the 0.5mm² wire onto the spool and there is capacity for more still.

Printing your own!

I shall be sharing the STL files so anyone else can print some for their own portable setup. I’ve not uploaded them yet as they are freshly off the press (printer). These are printed in PLA+ and seem fine. PETG would be even better. I printed with 4 walls and 25% infill. The holes for the M3 studding I clear out with a 3.0mm drill bit in a battery drill which I think is better than making the holes oversize enough to be a clearance on the M3 studding. The hex centre for the driver bit has enough clearance to not require post printing attention.

STL files as of today can be downloaded here:
https://www.thingiverse.com/thing:6928231

The GM3SEK mains filter

I’ve looked at the GM3SEK mains filter several times but nevertaken it any further. My worst noise at home varies with beam heading on HF so I suspect it is being received by the antenna itself and assume filtering the mains would have no effect. But recently I was testing an antenna on 80m and noticed quite a bit of noise from the Honda EU10i generator I have which wasn’t there (as I remember) some years ago on 80 using the EU20i. So I decided I would build a GM3SEK filter to try to stop the generator noise and as a side effect, could see what happens at home!

The starting point is on Ian’s site here:
https://gm3sek.com/2019/10/11/clean-up-your-shack-2019/

Ian details all the parts with links to vendor’s sites and manufacturers part numbers. I was able to source all the parts needed from CPC and Farnell, and not pay delivery charge (I bought 2 sets of parts because I run the amplifier from a second 240V outlet so would need a 2nd unit if I used them here.)

From Farnell I ordered the below. The 13A lead for the mains input.
Prices include VAT.

Order NumberManufacturer NumberPrice
1304848FN2030-16-06EACH£24.02
FN2030-16-06 FILTER, 16A CHASSIS MOUNT
4156104431177081EACH£16.19
0431177081 SPLIT CORE FERRITE, 375 OHM, 25.15MM
1124373X-150708AEACH£8.70
X-150708A LEAD, 13A, BLACK, 2M

From CPC (also including VAT).

Order NumberManufacturer NumberPrice
EN84544GR17012EACH£10.62
CE-TEK GR17012 IP65 ABS Enclosure – 170x170x75mm
CBBR7352PP01645EACH£0.26
PRO POWER PP01645 Nylon Cable Gland PG-11 Black, Single, IP68
PL15548WP21-01EACH£12.90
BG ELECTRICAL WP21-01 13A 1 Way Outdoor Mains Socket
CB22778PELB0767EACH£15.01
PRO ELEC PELB0767 3183TQ 3 Core Heat-Resistant Mains Cable, 2.50mm, 25A, White, 5m
CN19163CTSOS431/12EACH£1.36
CAMDENBOSS CTSOS431/12 Terminal Strips, 12 Way, 2.5mm, 24A

You’ll notice the 2 Fair-Rite oval cores 2643167851 are not there, that is because I have several in stock already. As I write this these are available from Mouser for £3·77 each here:
https://www.mouser.co.uk/ProductDetail/Fair-Rite/2643167851

CPC delivered next day, Farnell the day after. Which is interesting as Farnell is the parent company of CPC!

I started off fitting the main box. I used tha samebasic layout as Iam GM3SEK used, why change a winning formula. The chassis mount filter fitted with M3 screws and nylocs. I always use nylocs in general, but especially when plastic is involved as you can be sure of a safe fixing without excessive force.

Next I drilled the hole for the gland, which needed a 19mm hole. Drilling large holes with a twist drill, even going up in steps from a small pilot hole, never works well on plastic boxes. The drill wants to tear out as soon as it breaks through. Far better and faster is a step drill which even deburrs the hole for you with the radius leading to the next size up:
stepdrill for drilling large holes
However, do ensure you mark the hole in the right place, UNLIKE me! Doh!
poorly located hole for gland
The hole is too close to the corner for the nut securing it to sit flat. I need this to be watertight for portable use. I toyed with the idea of scrapping this and using the second box but in the end I bodged it in by removing plastic with the dremel:
poorly located hole bodged up
Managed to get the gland fitted better after the mod:
gland fitted after bodge
Next I stripped the outer from the 2.5mm 3 core. I made shallow slits with a knife both side and peeled back the outer sheath. I used adhesive lined heatshrink to keep the ends together before fully stripping the whole length. I started with 2.5m of cable. Ian says 1.6m but I knew I was needed longer tails than his build.
3 cores heatshrunk together
Once fully stripped I did exactly the same as the instructions, twisted it with the battery drill.

I wound the large split core first then prepared the two oval cores.
I didn’t want to superglue them so I used a strip of double sided tape:
oval cores about to be stuck together

I then used the desktop and a square to align them up nicely to stick them together. This method would work well with superglue too:
square used to align oval cores
Winding the 3 turns through these was a lot easier than the larger core.

Here are the two chokes wound and rulers showing the spare length. 30cm on the input side and 75cm on the output side. So 2m would probably have been plenty. But it’s easier to cut some off than add some on.
extra length left over
Soon I had wired the input cable and the choked cable to the chassis mount filter. I stuck down the 2 oval cores choke with mode double sided tape. The large choke touched the lid so not required:
main box completed
You’ll notice I only have one gland fitted to this box. As this is designed for my portable operating I want it to go between the generator and my extension lead so I am using a single waterproof outlet (the 3rd item from CPC above). This was fitted to the main lid with M4 countersunk and more nylocs and a centre hole for the output cables:
outlet box fitted to main lid
main lid inside view
Before fixing these together I applied a ring of silicon mastic around the 5 holes to keep water out:
outlet box sealing to main lid
Output cable threaded through and lid fixed in place:
output cable to outlet box
Once the outlet socket was wired and fitted it is ready to test:
finished filter with waterproof outlet
The input lead is kept short, just enough to leave the generator and sit the filter box on the ground.

I’ll add my findings to this page when I test it.

TMF-3 based DXcommander style vertical portable antenna

This is a build of a TMF-3 based DXcommander style vertical antenna for portable use because at home I just do not have any space for anything on the lower bands. Also, when I did put up an inverted V once for 40m (hell of a job) it induced so much RF into the house it was not a great plan.

The basics of the DXcommander style verticals are well know, I won’t be going into that. This is focused on making use of my TMF-3 50 foot (15 metres) heavy duty fibreglass push up mast that O bought during lockdown, used for a while to support my lightweight 20m moxon but has been doing nothing since.

This video shows the TMF-3 mast and the guying points I have already made for it (excuse wind noise):

The TMF-3 at 50 foot tall is a beast of a mast and I have not yet fully extended it vertically. The garden was too small to get a decent angle on the guys to push up any higher than about 30 feet. I have added guying points to the mast, one atop the first section to secure it to push the rest up and one just above half way up. But the issue for me using it portable was to be able to anchor the bottom securely to work with the 1st guying point and of course enable connection of radials and radiators. So this is what I came up with:
TMF-3 based DXcommander style vertical base

This video explains the features of the base in more detail (excuse wind noise):

And this video shows a test fitting (excuse wind noise):

This is a push fit top for the very top of the mast that I drew up and 3D printed. Even though the mast is 15m tall it’s still too short for 80m so my plan is to take the wire over the top through this and out to the side at an angle and pegged to the ground via a length of cord.

Update 1st April 2025

I have been working on other projects so this has been sidelined a little, but one of the things putting me off progress slightly was the thought and bother of laying out and packing away all the radials. I have to do my testing portable where there is space but didn’t want to spend half the day dealing with radials.
So some progress I HAVE made is coming up with a winding and deployment system which I have described here:
https://g1ybb.uk/the-ybb-wire-winder-system-for-radials/

And the results look like this:
YBB Wire Winder system loaded up
I am completing some other projects (for example https://g1ybb.uk/mini-lathe-cross-slide-modification/ ) and with the less Wintery weather coming I should be back onto this one soon!

To be continued…..

 

Wire guides for moxon or cobweb

I have had a few emails now from people asking for STL files to print themselves some of the wire guides I have used on my disguised cobweb or my 20m wire moxon. So I have uploaded 3D printed wire guides for moxon or cobweb antennas in various different sizes for free download.

3D printed wire guide shown fitted to fishing pole

I have no idea what size tubes other people are using so I have made a set that covers poles from 7mm diameter up to 25mm diameter in 1mm increments.

Each size should grip about a half mm diameter smaller than design and expand about a half mm bigger diameter.

They are designed for M3 machine screws and I recommend using nyloc nuts so they can be nipped up enough to grip without over tightening.

The wire holes are 3.5mm diameter which is bigger than the tri rated wire I used on my 20m moxon so should be fine for most people. Of course you can easily run a brill through the hole if you are using very thick wire but be aware of making it too weak for such thick wire.

To print orientation below is best for strength and doesn’t need supports. I recommend PETG and print with several walls also for strength. I print mine basically as 100% walls so there isn’t actually any fill as such.

best orientation to 3D print the wire guides

Download the files from the link below

https://www.thingiverse.com/thing:6680276

If you like them, I’m always up for a coffee…
https://g1ybb.uk/buy-me-a-coffee/

The YBB boom tether system

Like many hams, when there is a lot of wind about outside I have to check on how the mast is doing. One thing I did not like was the way the wind rocks the beam back and forth on the rotator. I figured this cannot be good long term of the gears, especially as they seem to be mostly plastic. (Unverified)
When you have something like a 20m moxon up the play back and forth looks quite dramatic. So here I am sharing my YBB boom tether system idea.

For a couple of years now I have had a small arm attached to the stub mast and I guyed that down but it was very short and even with a lot of tension the boom still moved about in bigger winds. Also was quite a lot of  sideways downforce on the rotator (I don’t have a cage).

So in the design and build of my new 20/15/10m tri-band 2 ele beam I incorporated a tethering system on the boom itself at each end to have more effect and balance the side loading to the rotator.

This has proven to be very successful, keeping the boom practically motionless while the 20m moxon element dances all over the place. So I thought I would share it as an idea for others, especially those with a christmas tree stack of beams. I always retract the mast when not on the air, but I know others also retract their masts when high winds are due, and this could help then.

This is the mast retracted to about gutter level and the beam tethered. The left hand tether point is close to the 20m driven because the balance point of the beam is to the left of the 10m driven so it was a small contribution to try and reduce the imbalance on the mounting point.

triband beam tethered

The tether points are very simple. Some aluminium angle, a square U bolt and a round U bolt. These MUST be stainless. (Trust me I know!)
tether point detailTo hook the rope on these I use a plated steel (must NOT be stainless) clip from screwfix. I then file the head off the gate pin to remove that.
Smith & Locke Karabiner 10 Pack

Then this is what they look like installed:
tether fitted detail

Once fitted they are just tensioned up with sliders as I use on all my guy ropes:
tether rope sliders
Now I know by now you are wondering how on earth I get them on and off?
Well that is quite simple and surprisingly easy. I use a telescopic fishing pole with some neodymium magnets taped to it to both fit them and remove them for winding the mast up:
tether fitting pole
All dead simple stuff but it is really effective.

2 ton arbor press tune-up

This may not seem that radio related but an arbor press is a very useful tool, even if it is not used that often. Most recently I have used it to press in my YBB washers into Stauff clamps for an antenna build. I’m tuning it up in order to use a 5 inch vice based brake press set to do some sheet metal folding, mostly as I don’t actually own a vice to use the brake press set in but also because if I did I would only have a couple of inches of throat to bend whereas the arbor press will give me about 5 inches. These are great tools and not expensive but out of the box they don’t feel or work that great so I decided it needed a simple tune-up.

2 ton arbor press
I actually bought an arbor press because I could get what I really wanted which was a lever press RS (Radio Spares) used to sell. If you have one of these in good condition, I need it!!

RS lever press
I used to have access to one of the RS punches in my previous company and used it to good effect to bend boom supports for my VHF yagi. That was the actual original reason I got the arbor press later, despite working now at a company with several fly presses, I like the control of a lever.

Anyway. You can see from the following video that as supplied they are a bit rough and ready:

Having seen videos on youtube about these already I knew it could use a strip down and clean up. So it was all stripped down and taken outside to clean the swarf from the tapped holes that hadn’t been done when it was made. As I don’t have an airline at home I used a steel tube and blew hard, after first spraying in some WD40 to loosen it and wash some out:

Once all the holes and bolts were cleaned up I used a fine file to smooth off sharp edges and machined faces that weren’t that smooth. The side to side slop adjustment of the ram is just two bolts that nip up onto the side of the ram so I also filed the ends of those smooth. Below is an after and before picture of the two bolts, one filed, one as supplied and fitted:

adjustment bolt filed
The adjustment screws that control the front to back slop act on a small plate but that plate was just guillotined sheet steel and not deburred at all so had a sharp edge on the pressure face so that was all filed smooth and flat too. (You can see that plate on the edge of the video below)

Once all the filing and cleaning up was done I first fitted the lever arm spindle and lubed it up:

I then greased up the 3 sides of the ram and fitted that and the front plate, and then adjusted all the adjustment bolts:

That will do for now, but there is a mod people do where they grind the bottom 2 teeth off the ram which allows you to be able to position the handle in the ideal position for the depth you are pressing. I will also drill and tap some holes for adding fixtures to the arbor press, such as the brake press kit (see below pic).

vice brake press kit

DK7ZB dual band 2m+70cm yagi

This was another Covid lockdown project in 2020 to enable me to do some over the air audio checks with locals and maybe give some points away in contests to the locals (my QTH is very poor for VHF/UHF). I wanted something small I could put in the attic. I figured a simple DK7ZB dual band 2m/70cm yagi in the loft with a single feeder would be ideal.

on this page:
https://www.qsl.net/dk7zb/Duoband/4+5_2m-70cm.htm

Martin DK7ZB describes his design for a single feed dual band yagi with 4 elements on 2m and 5 elements on 70cms on a compact 1m long boom.

I already have my element cutting jig  (see here) so cutting the elements was easy enough as usual. I went for the 8mm elements to make it nice and light.

To assemble it I decided I would 3D print not just the dipole box but also the element mounts themselves. The beauty of this over commonly used mounts like the Stauff clamps (see here) is I could design in a feature to ensure the elements are nice and perpendicular to the boom. I also don’t like drilling my tubular elements. For a start it weakens them and also adds a place for inaccuracies to creep in.

So this was my design for the element mount:
element mount design

A snug fit onto the 20mm square boom and a friction fit for the elements. It was printed on its side so that the layers of the 3D print went around the element as printing as shown it may break off half of the tube pushing the elements in.

The are secured from below as seen here with an M3 bolt screwing into a captive hex recess in the mount:
element mount fixing

I don’t like droopy dipoles on my yagis so I printed a dipole box to house the 50ohm choke that has integral clamps outside the box and also extra support inside the box:
3D printed dipole box

I wanted the dipole box to also align on the boom but did not want to print it with supports as they are messy to clean up after so I used a simple locating spacer with 2 matching fixing holes in the dipole box. The 3rd hole in the spacer is a sighting hole that matches up with the scribed line on the boom for the dipole. This was also used as a drilling jig:
dipole box spacer + drill jig

I used the dipole box spacer/jig to drill all the element fixing holes exactly centre of the boom and on the scribed line and assembly went to plan. I didn’t take photos inside the dipole box on this build but the following image is from a previous build of a 50ohm choke fed DK7ZB design. I hadn’t added the extra internal dipole supports here but I did print the choke former and re-used the design in this build.
dipole box wiring

Before final fitting of the elements I added a coax support guide. I usually use LMR400 as my feeder which is great but not super flexible and I like to take strain relief off the dipole box and N socket. This slips over the boom and supports the coax and also helps you align the N plus so you don’t cross thread it:
coax support guideHere is an end on view showing the coax support perfectly concentric with the N socket and with a radius to match LMR400. When the feeder is fitted I then use a velcro cable strap, the ones with a slide through buckle you can tighten onto:
coax support end viewSo finally we have the finished dual band yagi ready for testing. The boom to mast clamp is another G1YBB design for maximum flexibility and minimal RF footprint when looking along the boom. The guy ring is also G1YBB designed and seen on this link:
dual band yagi up for testing
And how does it look on the antenna analyser? I like making antennas and try to make them precisely because I do NOT like fiddling and adjusting much (wire stuff is OK) so my methodology is to try and follow the design with high level of accuracy and hope results match the design.

144MHz SWR plot:
Dual band yagi 144MHz SWR plot
432MHz SWR plot:
Dual band yagi 432MHz SWR plot
Both are a little high in band especially 2m but the SWR curves are so flat it’s very usable on both. I ended up feeding this yagi in the attic with RG58 as it is easier to route so with the losses in that the radio sees no reflected power as it is mostly used in loss I imagine. However I have made QSOs using this antenna in the loft, fed with RG58 on 23cms using 10W from the IC-9700. I can’t imagine much of that 10W getting to the antenna and what does reach the antenna has to pass through the roof but QSOs have still been made several times.

The YBB Washer

So many commercial and home brew constructors use Stauff type clamps for attaching yagi elements to the boom but I have until now avoided these because I hate the huge bolt holes that are typically at least 6.5mm in diameter which is sloppy even on a grossly overkill M6 bolt. Of course these clamps were not designed for making antennas but are extremely useful as they come in pretty much every tube diameter there is. So after many builds avoiding these clamps I decided to come up with a way to use them that would satisfy my exacting standards. One night instead of being able to sleep I came up with the YBB washer.

Stauff clamp example

Usually instead I have been making my own elements mounts in some way or other but I am building some HF beams and it’s just convenient to use off the shelf Stauff clamps so I decided I needed to do something about this issue. I recently assembled a commercial beam that had a tapped boom so next to no slop bolt to boom but you could move the element side to side about ±6 inches or more at the ends of a 50MHz element. I had to use a square to mount them:

squaring the elements

So I set about as usual pondering (usually when I should be sleeping!) over how I could stop all the hideous play. Another good thing for me about the Stauff clamps is that they provide 3D CAD models for free download so I was able to download some and do some thinking. I prefer to use much smaller bolts like M4 for my antennas which is more than strong enough in a good design. My 2m and 70cms elements are held on with 2x M3 bolts which is also more than strong enough.

The recess in each half for the bolt head according to the 3D model is 12mm diameter, so I decided that a simple solution would be 2 delrin or similar washers 12mm round with a 4mm bore fitted to the half nearest the boom/mounting plate. They are not needed in the top half because the top clamp will self centre onto the element tube:

The YBB washer design

That would do it I decided. I have a very small lathe and I checked I can easily buy rod in 12mm diameter.

G1YBB baby lathe

Next step was to get some Stauff clamps ordered to ensure they matched the 3D models I had. On measuring the bolt head recess they were actually more like 12.4mm (at the top anyway), probably due to needing slight draught for injection moulding. Hmm. Next size rod size was 14mm. I do have the lathe, but I’d rather not turn down enough rod to make dozens of washers. I wanted to just drill and part off. I decided to check the supplier notes on tolerances. Some good news there! as most of these materials are very often turned down, the tolerance was stated as +0.2 to +0.7mm. Good stuff. Let’s get some in. I ended up ordering acetal for its low absorption quality and as it was very cheap!

Once it arrived I did a test fit and the bar fitted a couple of mm deep into the bolt head recess then started getting tight, that draught taper I imagine. Ideal. So it was off to my baby lathe and get to work, first running a 4mm drill up the centre then parting off 5mm lengths:

The YBB washer pair

Next to press them in. I discovered that the 16mm and 12.7mm Stauff clamps had an ever-so-slightly larger bore bolt head recess than the 10mm Stauff did. And coupled with the slight edge burr from parting off (seen in pic above) it would have been impossible to press them in by hand. However, I already have an arbour press that I got for forming bent box section boom supports, so in a couple of seconds they were fitted easily:

pressed in with arbour press

Soon I had a complete set of Stauff clamp pairs with captive washers on one half only:

finished set of clamps pairs

The proof of the pudding is in the eating or something along those lines, so I thought I best test them! The day before I had drilled out the mounting plates for the 2 beams we are making so I clamped one in the drill vice and just fitted two M4 bolts into the holes to see how it worked:

That’ll do, as the Yorkshire based advert says… I am happy now that single clamps on the boom will hold a 50/70MHz element securely and square. And once you get to 2 clamp pairs on a 28MHz element or bigger there should be no play at all.

Many might say that this is all overkill and 1000s of antennas have been made and used very successfully with none of this effort. This is of course true but I like to build ALL my antennas to exacting UHF accuracy including the HF ones. I think attention to detail is worth it and my VHF/UHF contesting results using my home brew antennas makes it worthwhile.