Build Your Own Model "T" Windshield

ahhunnn...pwpwpwp ahhhunnn...pwpwpwp Wha? What? Sorry, I fell asleep, bad physics do that to me...and engineers, wannabe or real...

That same vehicle with the steel framed windshield you have, does it have the original wooden floor? Or the original wooden structural framing? Just curious...

 

You must have been abused by an Engineer at an early age, eh?

 

You've already spent a lot of time and money. The windshield is the wrong area to go cheap. The one you have is an eye sore compared to the rest of the build.

 

I agree that this thing is too tall and needs support rods to keep it halfway rigid. With my luck, I can just see it folding in half and landing on my lap at speed!

Something you might consider is to use that black windsheild glue that is out there now for the newer cars, etc. Some of that stuff in the channel of your frame may offer a bit more support for both the frame and the glass as well.

Personally, I think you'll be fine, but I hesitate with it being that tall. If it were me, I woulld look at possibly building another frame (yeah, I know - quite a bit of hassle) and use a sheet of something like lexan to experiment with and bring the height of the windsheild down to a shorter but effective height.

Otherwise, I applaud the do-it-yourself attitude.

 

i understand about the 400 bucks being a huge factor in your choice. as much as i would like to commend you on your windshield........i can't. sorry but that is a hazard to you and who ever is riding with you.

there are other ways to put the windshield on your T. the alum shower door channel for one, or a length of 7/8" alum round stock with a 3/8" slot cut in it. you have a router. you could do the slot your self and have the pieces tig welded after.

i can buy T frames all day long for 20 to 40 bucks on e-bay with the shipping. i bought a complete one for a '21 for 113 bucks 3 months ago, that was both upper and lower frames, the stanchions, hinges and it ever had the glass in it.

please give some thought to doing something different here.

Ron

 

Keep in mind the head wind factor.

You can end up traveling at highway speeds and have a total windspeed of well over a hundred.

 

i dont think you would end up haveing 2800lbs of force on this windshield, i think air would pile up infront and then cause the NEW wind to go around the sides on the frame, who has a wind tunnel we can test this design? you could also attach the frame to a roof rake of another car and go for a spin down the high at twice the speed limit just for a margin on error, no one wants a face full of glass.

 

I am a person of modest education. So the guys that responded with math calculations and engineering insite were of keen interest to me. Thanks for sharing your knowledge!

Lakeroadster's response was a good illustration. The numbers he used though are hardly appropriate for my Jalopy. Using Lakeroadsters example, let me adjust the numbers to something more in line with the car's use, history and dimensions...

If my T's life so far is any indicator, It has never been on the interstate or farther than 100 miles from home. Add to that my Granny-like driving tendencies and it's underpowered six cylinder motor. 50 MPH seems to me to be a more appropriate speed for calculation purposes.

For the sake of easy calculation, lets assume 50 MPH is 2/3 of 70 MPH. Assuming that, it brings our 2 PSI force down to 1.32 PSI

The actual dimension of the windshield is 39" by 20" - a common size for "T" windshields in most catalogs (neither too large or out of proportion). This equates to a 780 SQ. IN. surface area.

Multiplying the 780 SQ. IN. surface area by the 1.32 PSI results in 1,029.60 LBS of force. This figure is far less than half of the frightening 2,880 LBS of force in the previous calculation.

Call it folly, but I think in light of how my "T" is driven, this will be more than serviceable.

Keep in mind the project is not done yet. It will be secured with better hardware and have the benefit of the support rods when finally completed.

The courtesy, diplomacy and tact of every one responding has been much appreciated. No one has shouted "You Craphead! You're doing something stupid!" Your restraint is admirable! Thank you!

In light of the controversy, perhaps a long term test is in order. I have always prided myself in being a humble & fair-minded person. If I turn out wrong I will gladly post as much. In the mean time, I plan on completing the project and making additional posts thru finish.

I'll post in the future at six month to one year intervals to share how it is holding up.

Wish me luck!

2$ Bill

 

Assuming that your calculationsare right and my gut feeling is that they are low but even if they are then:

Multiplying the 780 SQ. IN. surface area by the 1.32 PSI results in 1,029.60 LBS of force.

Do you think that windshield frame can support a half of a TON?

 

He will learn

 

i would rather get smacked in the head with a piece of steel than to have my head cut off by a piece of glass.
this almost seems like a DARWIN award waiting to happen
or worse yet you could have the windshield come off and kill someone else
it sounds like you are definatly a man of modist education so i will ask you to please not run this setup
for your sake and mine
tk

 

I have to agree with everyone about strength.Owning a T bucket & can tell you that theres a tremendous amount of pressure on the windshield.you HAVE to run rods to the front for one thing( I used 3/8" brake lines with 1/4" inside it, flatten the ends & drilled holes in it & it worked great & was cheap) put them about midway up.Even then i'd be real leery of it.
we where in a friend of mines 30 roadster & the windshield folded back against the steering wheel at about 60 MPH, even at about 10mph we couldn't push it back up.
If you can find a book called"how to build a Tbucket on a budget" he tells ya how to make a windshield frame out of conduit, worked great & he buffed it out like chrome.
One other thing the windsheild looks too high.Try to lower it.Mine is high & its a 2 piece, i always run with the top angled back a little & in the heat i open the bottom.Improves my gas milage by about 20% lol
JimV

 

I had a 27 t roadster with aluminum windshield posts,Polished and purdy. With no supports going forward.I had the top on traveling across Nebraska.I was going 65 mph and a prety good headwind coming at me. One of the posts snapped in the middle and dam near got the top ripped off and a windshield in our face. It was one of those OH SHIT ! moments.We took the top and the windshield off and made the rest of the white knuckle trip to Colorado in the wind. Later I installed supports with no further problems. That is a lot of flat surface your pushing through the wind.

 

I agree with the ebay choice vs the wood due to "a little more on safety" cost and time. your wood working skill are very good though and I was wondering if you do top bows or wood spoke wheels at all?

~J

 

forgot to bring this up, but if you use the wood windshield why don't you cut a groove maybe 3/8" all around the back, make a steel frame out of sq stock or round stock, put it in the groove & cover it with bondo.You can even skim coat the wood with bondo to give it a real smooth look.

 

Thank you for the good laugh, seriously. Yeah, I do have a tendency to go off about engineers, and I know there are some good ones, but I've had too many experiences with the difference between what calculates out and what really happens.

I look at it this way, yes, there is a substantial amount of force exerted upon the windshield at speed. The frame, however, will not see the full brunt of that force, the majority will be spread across the glass. Think of a shelving unit that is rated for 750 pounds, but has a top made out of 3/8" particle board. If I were to exert that force of weight in a concentrated area, the shelve would fail catastrophically. By spreading the weight, hence force, the shelve can withstand it.

The only concession I would make at this point, in terms of the wooden frame, would be that when Mr. Bill D) assembles his forward struts for the windshield, use a metal backing plate behind the frame in that area, then use threaded inserts behind and through the plate to the front of the frame. This will allow the force to be spread over a sufficient area so as to alleviate the immediate impact at the point of connection.

Mr. Bill (sorry, I just can't resist) has gone out of his way to design and implement an idea contrary to popular belief. I, for one, am impressed by his entrepreneurial spirit and commend him for his efforts. If he fails, he has failed successfully, going to that place that all of us strive, being unique in our efforts and fearless in our pursuit.

...and yes, sometimes just because something can be done doesn't mean it should be done. I just don't think this is one of those situations.

But then again, what the heck do I know?

 

Let's be realistic the post mounts in the fiberglass body will fail before the wood frame will, remember they are supported by.............wood. Knowing Bill's use of his T this will serve him well for years to come.

Ron

 

Theres an old boaters trick, you get fiberglas resin & mix it with the normal amout of hardener.The double it with acetone.So now you'll have a "soupy" mix.Get a paint brush & paint the frame with it.It'll just look like its wet.Thia will penetrate the wood & strengthen it alot.Try a small amount on a scrap piece first.
Also i can't agree with Ron the posts are bolted from the side & unbelievably strong.Mine also doesn't even have wood behind it, & its still tuff.
I heard a story once about a guy who wanted to see how fast he could go in his T(had a 2 piece W/S in it) It was said that when he had it up alittle over a Buck he looked at the glass & could see it bending in!!I beleive it..Next time you're doing 50-55 on the highway stick your hand out the window, palm flat & see if you can hold it there.
JimV

 

You are incorrect. The frame does see the entire brunt of the wind load. The glass transfers the load to the wood. This load is then transferred to the supports where they fasten to the body.

Using your analogy of 750 pounds on a shelving unit, yes the shelf itself can have the load spread across it but the 2 sides of the shelving unit see the full loading, thus 375 pounds a piece.

Take Low Lid Dude's first hand experiences to heart and use a sturdy steel windshield frame. This is one area where you do not want to take the trial and error approach.

John

 

Plus it looks like shit. Might as well hang a couple of brass lights out there off of it!

 

I did a little scaling of your height vs windshield height.

You could chop the windshield and look over the top of it.

In roadsters, the bubble of air over the windshield goes up and over and you won't be hit in the face with the full blast of wind.

You may find that a ball cap or similar will get sucked off if you look up, but part of that can be due to side winds.

Airflow doesn't strike the bottom to middle of the windshield head-on either.

If you get a chance to take a ride in a roadster - topless or not - during a rainstorm take note of the water flow on the windshield.
Tells a tale it does.


Along the lines of oak strength vs steel, the Model T windshield frames aren't all that big and hot rodders have been running those successfully for many years.

Right now, besides the strength question the roadsters design lines don't flow well, but would with a shorter windshield.

Chop the windshield, add support rods, wear shades during the day and get a tie-on hat like some of those NZ or OZ river runner hats in Cabela's.

Heck, even the $8. boonie style gardeners hats at True Value work well in roadsters....

 

the windshield itself wont fail.. it is the mounting of the windshield is the problem...the wood will split once the screws and bolts mount..

I too think it is too high.. chopped a bit would look better...

I work with wood alot and know its limits..that is why I run hide steel structure inside all the wood bodies and doors..every little bit helps

wood

 

I'd agree that without at least support rods it's an accident waiting to happen-even at a mere 50 MOH. It's way too tall and throws the car out of proportion.
I realize $$$ is a problem, but your $400 quote is a catalog price. Buy a used T windshield frame-or make one from tubing. You'll be into a metal frame for less than $100. You may even be able to have the current winshield cut down to fit the new metal frame.
If $$$ is an issue, sell something that your not using to finance it or brown bag it to work; $10 day X a month or so and there's your windshield $$$.

 

All of us work with steel. We weld it, bent it, shape it, drill it, rivet it, ect... Becuase we are all so familiar with steel we get the mistaken notion that using anything else is inferior. Steel is great stuff to be certain, but, wood is still a very viable construction material.

LOW LID DUDE related a story about metal windshield posts snapped off, nearly ripped off the top and almost got a windshield in the face. That horror story was the result of metal failing. Time, vibration & fatigue caused that metal to fail. The natural property of wood is a good defense against that problem re-occuring.

Consider this:
Even yet today, with improved metallurgy and chemists creating wonder composite materials, wood still is one of the preferred building materials for aerobatic aircraft... Aircraft that are subjected to far greater stresses than common aircraft.

Wood components of these aircraft are far more than just bulkheads, fuselage ribs and wing spars. Remember that even the propellers are sometimes wood. Think of the temperature extremes, weather/moisture, stress/force, vibration and fatigue that these aircraft endure. These examples are a strong testament to the capability of wood!

Wood is used because it is lightweight, strong, flexes under stress without failing and unlike steel it is not vulnerable to vibration or fatigue. Another plus is that wood is commonly available and easy to work with.

The natural properties of wood make it an excellent choice for a windshield frame.

I went thru airframe school and have worked with wood and canvas aircraft in the past. No doubt this background gives me a higher confidence in wood than other HAMB Brethren.

Truly guys, wood is good stuff! Don't nominate me for a DARWIN award yet! A wood framed windshield is not the death trap you may imagine.

 

i think you need to chop some off the top.. 3 0r 4 inches.

it might hold for a while, think you might try to impregnate it with the resin...

 

The cast aluminum 26-27 T Windshield posts sold for many many years were the simplest of castings and made by one vendor for at least 30 years. Same vendor made the cast aluminum short 17-22 T posts, tall 23-25 T posts, 28-29 Model A roadster posts, 30-31 Std and Dlx posts only and 32 posts and stanchions.
We sold 100s of sets of these every year with no reports of failures and no returns other than mismatched pairs.
I would point out that these early repops of 17-22 and 23-25 T posts all had the back ear(missing on most replacement posts these days) which has an essential 3rd mounting hole for rear support to prevent fore-aft racking.

Original 17-22 T posts are forged steel and have many variations in the shape of the lower paddle section of the posts.
Original 23-25 and 26-27 posts are stamped steel.

 

needs chopped, or a duvall style windshield like some of the cars in the first few posts in this this thread...

 

Original 17-25 T and 28-31 A roadster windshield frames are made of welded steel tubing with an integral glass slot. The corners are fusion welded.
There are cast steel inserts with threaded holes(for hinge mounts and post mounts on 17-22 frames and pivot studs i the 23-25 and 26-27) in them which slide into the tubing. These inserts give extra rigidity to the frame uprights and a solid mount to the pivots so the frames can be adjusted for air flow.

Original frames even if rotten are worth buying cheaply for the original steel inserts.

Original windshield frames, painted or plated, of all early Fords corrode from the inside out.

The new reproduction steel frames are made from steel tubing as original but the corners are not fusion welded.

You should be advised that original frames, even if they appear sound, may not be sound. The corner fusion welds are the weak spot.

I was ripping down the freeway on the way home when the upper left corner of my 23 windshield frame let go. Fortunately it did not fly back in my face but twisted and the glass cracked and laid back into my chest as I incredibly skillfully pulled to the side of the road in traffic so I could enjoy my cardiac arrest in peace.
I removed the glass from the frame and laid it on the floor. and pulled the frame back into shape and duct-tape it in place at the top of the post. My car uses full height original 23-25 stamped steel windshield posts.
When I got home and had a rare alcoholic beverage, I went out to see what had happened. The corner weld did not fail but the steel immediately abutting the weld on the top crossbar of the frame was thin, thin, thin. I rewelded the corner with my oxy/acetylene rig and had new glass cut the next day.
I ordered a new windshield frame the next day, used the original frame inserts and was on the road again in short order.

 

The profession of structural engineering has been characterized as "the art of molding materials we do not wholly understand into shapes we cannot precisely analyze, so as to withstand forces we cannot really assess, in such a way that the public does not really suspect the extent of our ignorance." Dr. A.R. Dykes.

 

I know this thread is about the windshield but please give some more details on the car. I see it is a glass body. Did you build it? What is that engine? A Ford 6 cyl maybe? Is it a low buck car and if so what did it take to build it.
I find the car to be very cool and normally a T is not my thing. Love the wheels and tires. What about a rear view picture? THANKS , Mark