Author Topic: DIY Fully Articulating Boom Arm you can make to use with Festool products  (Read 5450 times)

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Offline martin felder

  • Posts: 103
Boom Arm Version 1 in Randy's shop



That boom arm had a flexible extension cord and air hose, with the air hose now replaced by a plug it.  No sag.  Moves well.  Seems to be functioning perfectly.  However, version 2 will have a few minor changes with Randy thinking of ways to make beneficial tweaks.  For example 1 inch more space on each arm to allow a slightly longer flex hose which may allow cheaper hose to work as well, a bit more distance between the upper and lower pipes to allow more room for the hose and hose clamps etc. 

I now have all of the parts needed to try seeing if I can substitute the aluminum top and bottom plates and use 1 inch thick maple along with the wider thrust bearings to see if we can have the same functionality with easier-faster construction.

Seems to not be a question of it we can make the boom arm or not and have it work well, but if we can make a few changes to make it better, easier to make, and for even less cost.  Plans to follow after that.

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Offline jdm5

  • Posts: 106
This looks great!  Looking forward to seeing the plans!!!

Thanks so much!
Drank the green Kool-Aid...gave up counting long ago.

Offline ChuckM

  • Posts: 1840
Looks pretty good. Please also provide plywood thickness and tube size if possible fro reference.

Offline martin felder

  • Posts: 103
OK.  Made the articulating section out of wood.   Took very little time.  It ended up looking like this and worked perfectly.

For this, I had the 2 gears and 2 inch OD angled thrust bearings x 4 (links previously posted), two 3/8 hex bolts that were 12 inches long (Ace Hardware), some M10 hex bolts, some fender washers, and some lock nuts for the M10 hex, a couple of aluminum tubes (any narrow pipe will do), some 1 inch maple and some 3/4 plywood. 

So.... first thing was to cut some 1 inch maple - 5.5 x 9 inches x 2 pieces and cut the corners at 45 degrees.  That has nothing do to with function but looks nicer.  If you want it to look even nicer you would do a 3/16 or 1/4 roundover and sand.  I made no effort to make them perfectly identical.  As you can see, if you were to put the gears on top, they would fit

With the gears sitting on top of 1 of the maple pieces mark the center, and drill a hole around 1/4 inch deep with a 2 inch Forstner bit.

Then, keeping the wood clamped to the drill press table, change the bit to a 25/64 or 13/32 bit and drill the hole all the way through.  The center indentation from the Forstner bit is a nice way to know the center also.  This will allow a 10mm bolt to go through.  25/64 is adequate, but you can go 13/32 if too snug. 

This is key.  After you drill the first hole, Take one of the gears and place it as shown and use a drill bit or a 10mm bolt to keep it in place.  Then place the other gear next to is so it meshes.  Then, use a 24/64 or 13/32 brad point bit and insert it through the center bore hole in the gear, and tap it to mark the center.   Then drill the 1/4 inch hole with the Forstner, then drill the other hole through in the center.  If you were to then place bolts through both holes, the gears will mech.   Essentially, you are using the gears to mark the distance between them rather than a ruler. 

Now, on the left you see the 2 Forstner holes and the 10mm or so holes in the middle which are the prefect spacing for the gears to mesh, but we need to duplicate that on the other piece.  So, we put 1 on top of the other, and then use the brad point bit to mark the center.  On the picture on the right, the black arrows show the indentations.   For that piece, you drill the Forstner 2 inch diameter holes and the center holes.

Now, take 4 pieces of 1 inch thick maple 14 inches long and 3 inches wide and mark the center 1 1/2 inches before the end for each piece.  Drill the hole in that marking with the 25/64 or 13/32 bit and round the corners.  The center marking does not have to be perfect.

Now, drill 2 holes for the 3/8 long bolts as shown. Once you do that, then pub the 2 pieces on top of each other and do that same tap with the brad point to mark the corresponding location on the other piece and drill.  Then you assemble as shown on the right.  For this prototype, I used some 3/4 plywood for the arms 6 inches tall and 3 inches wide.  The 4 pieces of 1 inch thick maple were screwed to the arms.  For the undersurface of the top 2 of these, I drilled a hole in the gear and screwed it to the maple with a bolt running through so the gears would be centered. 

For the assembly, on the top, you have the top plate and the bottom plate with the 2 inch OD bearings seated into the wood (courtesy of the hole with the Forstner bit).  Under these plates, you have the extension pieces of maple connected to the boom arms with the gears under the top extensions.  Through the holes you have the 10mm bolts and washers and lock nuts.

I clamped it to the bench and tested it.  Worked perfectly.  I added 20 lb barbell plates to the end.  No deflection.  I lifted it up 7 ft and dropped it on the floor, no damage.  I swiveled it side to side and it never moved on its own but no resistance either.  No wobble or sag.

So far so good.  Again, this is just a preliminary report. I will provide way better detailed plans with more info on exactly how to attach the gears and assemble.  I think the aluminum is the best, but for those who want something more simple, and even less expensive, this seems to be an option that is super easy to make.
« Last Edit: June 07, 2020, 12:36 AM by martin felder »

Offline martin felder

  • Posts: 103
Oh... a couple of people are interested in making a YouTube video going over the instructions step-by-step. 

Offline Svar

  • Posts: 2148
If you want to simplify the design, you can replace gears with straps or cables as shown below (red). Straps attached only at the ends and transition from one curve to another. This principle is widely used for symmetric rotation from children's toys (Jacob's ladder) to industry.



« Last Edit: June 07, 2020, 03:39 AM by Svar »

Offline martin felder

  • Posts: 103
Thanks Svar,

If you have a link to a particular product for straps you recommend as a nice durable option, I can try it.  That would be as easy as unscrewing and removing the gears and adding the straps to see how well it works.  As far as design, I believe it is simple very simple to build with clear detailed instructions and a materials list now that the bugs are worked out.  The gears are just meshed together, and that guides where you drill the holes on the top and bottom plates. That correct spacing is all that is needed to insure the gears work when secured to the boom arm and the center section is assembled.  However, the if straps have identical functionality, and are less expensive, that sounds good!  I already have the gears and it already works, but as I said, I want to see just how easily it can be made at a low cost without compromising functionality and durability.  Therefore, happy to experiment so others can save $ if it works.

Offline Banana

  • Posts: 48
Perhaps a discarded fan belt picked up from a repair shop would suffice to test with?  The composition / lack of stretch / strength / ability to drill through for fastening etc. should exhibit the properties of a similar premium product. 

Offline casper

  • Posts: 19
A great build and good thinking but I am curious why the gears are used? Also did you consider Timken Taper bearings which are adiustable to some extent and having long rollers give more bearing surface area. The one big factor that may be a problem for some is they are not sealed at all. I have built one boom and it was a total failure though it was one piece with no articulation but you have given me ideas on version two. 

Offline Rchild

  • Posts: 5
The gears prevent the extended boom arm from over traveling and keeps them parallel to each other when rotating.

Offline Svar

  • Posts: 2148
A great build and good thinking but I am curious why the gears are used?
So it bends symmetrically. There are 3 sections to accommodate 360 motion. Gears prevent it from bending into Z-shape.

Offline Svar

  • Posts: 2148
Thanks Svar,
If you have a link to a particular product for straps you recommend as a nice durable option, I can try it.
I have nothing specific in mind. Just seemed like another alternative where you could use stuff lying around. As already mentioned drive belt could work well. Also, one strap could go on the lower hinge, the opposite on the upper hinge.

Offline casper

  • Posts: 19
Two observations, you can buy Unbrako bolts that are ground to size and fit with far less clearance in the bearings. Secondly, it occurs to me that if the gear was on top it would be under tension and not compression and this may result in less friction within the gear teeth and the tooth mesh could be adjustable if it was necessary. The mesh clearance could be done after the arm was fully assembled as well. I saw reference to another thread but can't seem to find it.
« Last Edit: June 08, 2020, 12:44 AM by casper »

Offline Bob D.

  • Posts: 1687
Maybe use bicycle chain for the straps. Strong, flexible, and readily available.
« Last Edit: June 08, 2020, 08:27 PM by Bob D. »
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It's a table saw, do you know where your fingers are?

Offline Cheese

  • Posts: 7511
Two observations,
1. you can buy Unbrako bolts that are ground to size and fit with far less clearance in the bearings.
2. it occurs to me that if the gear was on top it would be under tension and not compression and this may result in less friction within the gear teeth and the tooth mesh could be adjustable if it was necessary. The mesh clearance could be done after the arm was fully assembled as well. I saw reference to another thread but can't seem to find it.

You're referring to shoulder bolts, that was also one of my previous thoughts for the retention of the bearings.



I agree, any slight sagging of the arm will release pressure on the gears if they are mounted on the top of the arm. If mounted on the bottom, the gears could get jammed up.

Offline Michael Kellough

  • Posts: 4820
I like the straps idea Svar illustrated. Almost anything should work from nylon to neoprene. I’d go with neoprene because if you assemble the joints so the strips are slightly compressed that will also take care of the need to dampen movement.

Offline martin felder

  • Posts: 103
For the shoulder bolts, not sure if that applies to this design (wood version) but I could be mistaken.  On the bearings, I wanted them to be sandwiched between the top plate and the arms on top, and between the bottom plate and the arms on the bottom.  I wanted wide diameter bearings.  I found the 2 inch OD but the center bore was well over what would be used as a bolt.  So, I figured with the Forstner bit, that would seat the bearings, and the hole in the middle would allow the bolt to go through.  If it was not for the gear having a 10mm bore, I could have used 3/8 or 1/2 inch bolts. If a certain shoulder bolt is a good choice, I could try it out if given a link.  I think what helps keep the gears from being compressed or separated is the fact that there is support on top and bottom with a good amount of distance in between.  The bottom line is that what I have now is easy to make and is working perfectly and holding up so far.  I do not know how well it will hold up in 2 years until 2 years from now no matter what I do, but I am trying to stress it, and it is passing.

On these straps, if someone give me a link to a specific product, I am happy to buy it and try it. 

Offline Svar

  • Posts: 2148
Deep groove ball bearings are more appropriate here than thrust bearings. The load on them is mostly radial (through leverage of the arm) rather than axial (downward weight of the arm). Having said that, either one is overkill and will work fine.

Offline Michael Kellough

  • Posts: 4820
Changing my mind about using simple neoprene, reinforced flat belting would be better.

The McMaster page

Smaller width belts are the same cost. If you need two 3/8” belts you could buy one at 3/4” and rip it in two. You order by circumference so just get one belt a couple inches longer than the radius X2 for each side of the knuckle and then cut the belt in two equal parts. That’s two belts, or one that’s twice as long and cut it into four equal lengths.

Also, rather than reworking the spacing of the holes in the parts to try and compress the belting (to get some resistance to motion so the arm stays were you park it) and following Svar’s comments about any kind of (low friction) ball bearing being overkill, you could simplify drilling and reduce cost by using bronze bushings or steel sleeves. A little friction is good and the arm gives you plenty of leverage to easily overcome it.

McMaster page of 1/2” bore press fit drill bushings

I’d use ordinary nominal 1/2” bolts with these (usually a little smaller than the nominal size). Precision shoulder bolts will require precise drilling and pressing on bushings.

Another option is bronze bearings. Use ordinary bolts with these too.

McMaster page for DRY bronze bearings for 1/2” shaft

These won’t stain the wood. I’d use the largest od bearings so there is less wedge force on the wood. I’m a little nervous about the change to wood. If the wood holding a bearing splits the arm could fall? You could make it safe by running a bolt side to side through the wood.

Offline Rchild

  • Posts: 5
The way I have the bearing on the boom arm I made, seems to work perfectly.  I drilled and reamed out a hole to fit the 26mm bearing and pressed the bearing in..that bearing is NOT coming out at all unless driven out. With the boom arm that MartinFelder is making, the bearing is seated in the slot he drilled using the forestner bit.  It's not moving either and it works very well for what he is doing.  As for using straps instead of gears, what is to keep the strap from slipping off the rounded plate when rotated (since that plate is only 5/16" thick aluminum or..3/4" lumber if that's what is used) when slack on the strap is present? Perhaps some sort of "Lip" on the top and bottom plates?  The gear really does work well in keeping the arms aligned and was not hard to secure onto the plates. 

Offline Michael Kellough

  • Posts: 4820
Glad to hear it’s working well as is. What I posted might be better suited for another forum where the economy version is desired.

Offline Rchild

  • Posts: 5
What you posted is great..it gives more alternative ways to make this boom arm..all ideas are welcomed and encouraged.. I don't know everything..I can only attest to what I did for my boom arm..but I would love to hear better and easier ideas

Hei,

Very interesting development!

How about if you replace the gears with pieces of bicycle chain?
- fixed from both ends, and if falling down you could add nails or similar that gets on the slots in the chain.

BR. Simo

Offline martin felder

  • Posts: 103
As an update, the first boom arm was mounted to the bracket with a 6 inch long  3/4 diameter hole drilled through wood.  That worked out great.  On the next boom arm, it was not plumb.  The drill bit used was not long enough to go all the way through with 1 pass from 1 direction.  I figured that could be a problem for others.

So, modification using flange bushings



With this, you can use Forstner bits to drill accurately a short distance into the wood from both directions and have a larger hole in between so the rod is secured top and bottom.

Anyhow, getting close to final plans.  The boom arm works, but wanting to get a few things dialed in for upgrades that will make construction easier.

Offline martin felder

  • Posts: 103
Picture of the current mounting bracket



Picture of the boom arm mounted



In the picture of the mounted boom arm, it was taken as I was passing the power cords (1 plug-it and 1 standard).  It is fully functional with the wood version of the center pivot point.  Some day I will swap it out for an aluminum version.  It works and it is great having a working articulating boom arm in my shop.

My plan was to post a detailed guide at this point.  However, a couple of things I want to first upgrade.  On the mounting bracket, there is just a little bit of sag.  That would be remedies by shimming out the bottom bolts, but still a bit of sag when to the side.  That is not present on my friend Randy's boom arm and I am wanting something just right if I am going to suggest it to others.

Another imperfection is there is just a slight twist of the first section of the boom arm with the second arm off to the side, and I am thinking the first arm could be made a bit beefier, with care being taken not to add too much weight.  Along with that, I could have the first arm be a bit taller at the area of the mounting bracket to have a longer rod as was mentioned.

I would be curious if someone has a link to what may be a better option for a mounting bracket.