Headlamp on Helmet - Project in Progress

[Bolster]

I wear this Petzl helmet in attics and crawlspaces; saves my noggin from nails, concrete, dirt, and head bumps. Have always just slung a headlamp around it, but have been dreaming of a more secure mounting. So finally started. Was challenging to drill two holes in the helmet exactly 1" apart, and centered. (Also, this invalidates the warranty.) Glad that's done. No turning back now.

Now for cutting the mount. This was also tricky. Had to estimate the diameter of the helmet on the front part (effective diameter changes depending where on the helmet you are). Then also had to machine in a diagonal at the same time, since the helmet curves back. Here I've jury-rigged a rotary table with an extension and an auxiliary vise. The block of aluminum has been tilted to exactly 14 degrees, and the radius of the cut is 4". Slow going as the setup is not very rigid.

And here's the little b*st*rd after slotting and tapping. The slot is to lighten it a bit. It's .8 oz total. So much work for such a small piece. The outrigger holes are 1.4" apart and are for mounting a future light. Haven't decided which, or how many.

After stone-washing and a coat of clear lacquer, now mounted to the helmet. Nice tight fit, very secure. Reasonably low profile at 1/2 inch protrusion. Have run screws into the light-mount holes temporarily. The inner two holes are for the screws that mount the bracket from the inside of the helmet. Those screw heads are low profile, with washers to spread the load, and are underneath padding.

Now that I've got permanently mounted threaded holes, I need to choose a light. Am considering the H60w's that are in the mail. Don't know whether I'll mount one or two. I kinda like the idea of two, for redundancy sake. (Note that the headlamp strap mounts are back in place and still functional if I want to add a light that way, too.) What do you think, one light or two? Open to suggestions.

To be continued...

 

[Microa]

Neat and solid, well done. Will you consider one XML with 3 levels driver and remote Li-ion battery pack at the rear?

 

[bnemmie]

Nice. I know cavers and rock climbers use something similar to that with a universal slot system certain lights designed for that purpose have. This seems even more secure then that. Well done.

 

[Bolster]

Neat and solid, well done. Will you consider one XML with 3 levels driver and remote Li-ion battery pack at the rear?

That sounds great, but one issue I have in crawlspace work, is I'm often resting my head in the dirt while looking up at the floorboards. Which means the sides and back need to be clear. I only have the front of the helmet to work with; even mounting to the top of the helmet would snag on studs as I crawl around. Think of crawlspace work like constant tight-quarters caving, but without the possibility of getting lost.

But if I were actually caving? Heck yeah, I'd make a second mount for the back of the helmet for the battery pack.

 

[goose2283]

Wow... Beautiful work!

 

[Bolster]

So I need some help thinking this through. The clamp for the actual light (assuming an H60 for the time being) can be done two ways. First, you can make a cylindrical hole for the light to nestle in. You need to get that hole within a couple thousandths, which is doable. When you apply the clamp pressure, it is very evenly applied over the broadest possible area. This clamp I made for an H50 to a tripod is that sort, with very close tolerances and even clamping pressure over the widest possible area (for a given size):

But there is a downside to this method: it primarily fits one diameter well, no diameters larger, and with a two-point contact for diameters slightly smaller (not ideal). For example, this clamp for the H50 (.645) will not fit the H501 since the H501 is a slightly larger diameter (.650). Yep, 5 thousandths of an inch means no fit, since I made it to a tight tolerance. (The tolerance is so tight that just the lower half of the clamp alone will hold the light.) If I'd made it for the larger H501, I could clamp the smaller H50 in it, but clamping pressure would be primarily at two points.

So the problem with a hole that precisely fits a particular light is: pretty much that light only can be used, and lights of somewhat less diameter can also be fit if you're willing to clamp it at two points.

An alternate system is to borrow a concept from the V-block, used in machining to hold round parts.

A V-block contacts a cylinder on two points (if just one is being used), and if you made a clamp consisting of two v-blocks, one top and one bottom, you'd essentially have contact on 4 points, around the light every 90 degrees. The disadvantage here is that you'd have 4 "hot spots" rather than one even and widely distributed clamping pressure around a cylinder. Also this would be somewhat bulkier, to accommodate various sizes. But the advantage is that you could fit different sized lights (within the range of capacity of the V-blocks). I could probably switch out a variety of lights within the AA to the 18650 range if I went with this system. Ie, I'd not have to throw away my clamp when a new light comes along.

What do you think? Can you see any major trouble with the V-block system, as long as I'm not using crushing pressure to tighten down the lights? (Which you would not want anyway; they need to rotate or slip a little along the axis for vertical beam adjustment).

I'm also contemplating some sort of "padding," either a rubbery substance adhered to the clamp block (the hard way), or possibly a couple of winds of electrical tape or a couple of o-rings around the body of the light itself (the easy way).

 

[Microa]

Do you think to put flexible plastic sheets between the light and the clamp of method 1 is acceptable although the adjustable range is not big. Many cycling lights mounting to the handle bar use this method.

 

[tedh]

Sure, V-blocks should work. Two possible problems I can see -

1. As long as you don't apply crushing pressure, you're fine. But I worry about the person you loan the headlamp to, who just happily cranks down with the Allen wrench and dents (or worse) the light. As long as you know you're never going to loan it out, I think it's fine.

2. I would think the metal-to-metal contact requires a fair amount of pressure to keep the light from rotating. I'm not sure how much of a pressure "gap" there is between "enough to keep the light from moving" and "uh oh, I dented it". Seems to me you'd be wise to put a thin sheet of something in there to spread the pressure a little bit, and also to give you some friction so you don't have to whale away on the screws to keep it from moving around.

As another thought, what could you do to attach a hose clamp (or two) to the aluminum block? The hose clamp would spread the force around the round body of the lamp. It would look terrible, of course. Perhaps there is a more elegant hose clamp like mechanism?

Ted

 

[Bolster]

I would think the metal-to-metal contact requires a fair amount of pressure to keep the light from rotating. I'm not sure how much of a pressure "gap" there is between "enough to keep the light from moving" and "uh oh, I dented it". Seems to me you'd be wise to put a thin sheet of something in there to spread the pressure a little bit, and also to give you some friction so you don't have to whale away on the screws to keep it from moving around.

Thanks for thinking this through. No loaning so I'm good there. Made of aluminum so a v-block would be relatively soft. What do you think of encircling the light with a couple of o-rings before v-clamping? Hose clamp is very practical but I can't do it for esthetic reasons!

 

[Microa]

I'm also contemplating some sort of "padding," either a rubbery substance adhered to the clamp block (the hard way), or possibly a couple of winds of electrical tape or a couple of o-rings around the body of the light itself (the easy way).

Sorry, I omitted this statement.

That sounds great, but one issue I have in crawlspace work, is I'm often resting my head in the dirt while looking up at the floorboards. Which means the sides and back need to be clear. I only have the front of the helmet to work with; even mounting to the top of the helmet would snag on studs as I crawl around. Think of crawlspace work like constant tight-quarters caving, but without the possibility of getting lost.

The failure of the battery sometimes without any alert. Two lights are better than one.

 

[Bolster]

I tried the v-block solution on paper .... ugh ... it's a no-go. Takes up too much real-estate, looks clunky, would be heavy.

Back to the drawing board. I'm now experimenting with "shoe" designs, where you have a very simple mounting system with custom "shoes" for a particular light diameter. So far, I can get this design much more compact, lightweight, and it also appears to reduce the amount of machining necessary.

 

[Glock27]

I would really like an H50/H501 mount for a hard hat.
Could you machine them out of derlin?
O-rings sound great to keep from marring or squishing the tube.

G27

 

[Bolster]

So the latest design I call the "shoe rack" design. A vertical rack (actually two, a T-rack to the fore and a straight one aft), to which will be affixed "shoes" (or cradles) to hold the lights. Here's to scale for two H501s, because I don't have dimensions for the H60s yet. The lights would mount behind the main (front) vertical rack, keeping them close to the helmet and not protruding overly much. The shoes would be semi circular cradles to the precise size of a particular light's diameter, made of some sort of plastic material, but don't know what sort yet. This would allow for a "delicate but firm" grip on the lights. Picking the plastic will be important, because I think that epoxying the shoes in place is the best solution, and the plastic would need to be "epoxyable," none of the slick or oily plastics could be used. On the backside of the two lights (and four shoes) would be the second (smaller) rack, another vertical, held to the front rack by the two screws between the lights. Basically a flashlight sandwich, if you will. If the shoes are slightly inset into the racks, then there'd be very limited possibility that an epoxy failure would drop the lights, as the shoes would be locked into place.

This design has the advantage of compactness, and not needing a lot of metal around the base of the bottom light (which would hold the lights further away from the helmet). Also has the advantage that the front vertical "T-rack" will help protect the lights somewhat against unintended collisions. Lights are tucked in near the helmet (although the high one would be hanging out there farther). Have considered a back-bent rack but dismissed it due to machining complexity. Will likely add a "bumper" to the back rack, so the bumper hits the helmet before the racks have to bend backward. Rigidity of this setup is unknown, but planning the front and back racks out of .250 aluminum, that's pretty sturdy. Loose screws mid-rack would be catastrophic, would drop both lights. Am considering a 3-screw rack-attach solution (above, between, & below the lights) but that would make for a larger, bulkier mount.

To change diameters of cradles, you'd simply machine away the plastic shoes and the epoxy holding them, and epoxy in new shoes. So, an update every year or two would not be such a huge job. And some leeway of flashlight diameters would be permitted. Also, making a shorter T-rack would allow a lower profile single-light mount. You could change from a 2 to 1 light solution by replacing the rack.

@Glock - have not worked with Delrin. I'm not an experienced machinist (or designer, which is why I'm asking for criticism of my plans before I start machining). I don't know why you couldn't machine out of Delrin; threaded attachments would be my first question.

 

[kevinm]

Delrin threads pretty well, so that wouldn't be a problem.

The design above looks good. I'd move it down a bit, simply because I think your upper light is going to catch stuff, move the lights closer together, and move the bottom one closer to the horizontal piece.

Rather than o-rings, have you considered automotive hose? It's tough, would give you a clean look, would grip well with a little pressure, and wouldn't move as much as o-rings.

Here's a totally different idea: Why not use the block you have and mount one above and one below? Use one half of the clamp in post 6 for the top, one half for the bottom. With the bit of hose, it would be secure. You could even make a wider one that would cover the body except for the head and tailcap, giving you maximum hold and allowing you to change batteries without removing them from the mount.

Kevin

 

[Glock27]

I don't see a need for a double mount. Your nice slim minimal cool looking mount is turning into a monster. ;-) IMHO.

G27

 

[CarpentryHero]

Zebralight has some XML angle lights coming out, you may now need a double light.
Though if I were able, I'd build both set ups and have it swappable :naughty:
It gets dark early in the spring and fall here

 

[Bolster]

@ Glock: Appreciate the honest evaluation, and yes, at least a minimum of esthetics are important to me. Yeah, I'm concerned about monsterization, too. It looks bigger on paper, than in my head. LOL. And the mockup is with smaller H501s, not the larger H60s! So it would get larger yet. To your point, one H60w should provide plenty of light and runtime, 91 lumen for 4 hours or 37 for 10 hours. I have been considering both a single and double mount, but maybe I tackle the single mount first. A single mount would require a different setup, much more like the tripod clamp I did above. Downside would be, no redundancy. Just last night I had a Zebralight wink out with no warning (they're supposed to flash a few times at low battery!).

@ Kevin: Good idea re hose for aV block design, and that's two concerns logged about the height of the top light now. Moving closer together gets tricky, you can't see the slope of the helmet from the side but there's not a lot of room to slide further down. Also you need room for tapped holes, etc. Had considered the above/below-the-mount-block design, and laid it aside as it drops the light below the brim. Also considered a top/back and lower/forward design, but didn't pursue it as it puts weight forward, and allows the forward light to cast a shadow from the rear light.

Delrin threads, sure, but do the threads hold or strip? Esp. for the small threads required for small attachments? Machinists have concerns about aluminum threads holding, at least they're metal. I always make sure that my threaded aluminum attachments are plenty thick to allow at least a half dozen threads.

 

[tedh]

I'm still thinking the hose-clamp method has some merits. it's very low profile, for example. This system http://www.topeak.com/products/Xtras/BarXtender uses a stainless steel strap to attach to a bike handlebar. I wonder if a similar approach would work. You'd need a way to tension the strap around the light, and against some sort of block (probably padded). But in return you get a very low profile attachment method.

Might be worth a trip to the local bike store to see how they attach stuff to bicycles? Lights, handlebar bags, and so on.

Ted

 

[Bolster]

The H60w's arrived today. Forget about putting two of them on a helmet! They're huge (comparatively...to AAs). Definitely back to a single H60, if an H60 at all.

 

[ahorton]

I know you already have plans for this but one thing keeps niggling at me every time I look at this thread.

Why not grab a bigger bit of aluminium and build the whole light into it? You'd lose the angle adjustment, but you could probably get it pretty close to what you want and you're using pure flood anyway.

I'm imagining a block of aluminium approx 85x40x30.
20mm bore down the length to accept an 18650.
Threaded on the end to accept a screw-in plug.
Give one face a beautiful curve to fit against the helmet (like what you've already done). Angle it so that the opposite (front) face is perpendicular to the angle you want the beam.
Give the opposite (front) face a 20mm diameter hole (10mm deep) to accept an XP-G on MCPCB.
Add a step to allow gluing a 25mm diameter, 3mm thick polycarbonate lens.
Add another hole for a switch where ever you like it.
A 17mm driver should fit in the hole with the 18650.
Smooth off all the corners

You'd end up with something that looks like a brick that got pushed into the helmet.
Very, very solid.
Nothing to snag on.

Very few places for water to get it (silicone up the lens, add an o-ring to the 18650 plug and if you really want, you can use a magnetic switch)

This was what I thought of as soon as I saw this thread.



You could make it more compact by putting the LED and switch above or below the 18650. Make the cavities for the LED and switch overlap with the 18650's so that you can pass a wire between.