frankly i'm not sure if this is the right place for this post. the hamb forum confuses the heck outta me about what belongs where bla bla... maybe i'm a little dim. that out of the way: i'm building a t bucket more or less in the 60s-style and i am using a (transverse) leaf spring. it's a little involved as to why but the way i am mocking things up is with the spring with no load/body weight as mounted in the perch and it's my understanding the shackles should be about horizontal in this arrangement. but i have found nothing on what the pinion angle should be set at in this situation. i want 3 degrees up when it's all resting on the pavement; i understand there won't be much travel from unloaded to compressed but i don't know if i should set it at 4, 5, 6 degrees or what. it may be obvious i'm no old hat at this.
The pinion angle should be the same as the transmission output shaft angle. For example, if the transmission is 3 degrees down, the pinion should be 3 degrees up. Some fine tuning will be necessary as you get further along in your build.
100 threads. https://www.jalopyjournal.com/forum/search/901842347/?q=pinion+angle&o=relevance&c[***le_only]=1 AI answer https://www.google.com/search?q=pro...bjfzHHY-1zsgEoN1qdfM5wwInF7748s_Wn624&csuir=1 Hot Rod mag https://www.hotrod.com/how-to/pinion-angle-change The Driveshaft Shop https://driveshaftshop.com/driveshaft-angle-calibration/
https://eztbucket.com/shop/ols/products/rear-spring-hanger https://eztbucket.com/shop/ols/products/rear-spring-perch https://www.amazon.com/dp/B092R4919K/?tag=atomicindus08-20
You will only be able to have a "best guess" at this early stage. I strongly recommend that everything is only tack welded during the process. I would bet my left nut that you will have to modify and adjust as you go, and probably not just once.
Just to clarify this a bit....... What you said should be at ride height on the finished/loaded vehicle.
it's just now occurring to me you are likely right on. i would just like to get it in the ballpark so i'm not breaking tacks more than i have to.
that's my goal. the intake has a 3 degree angle at the carb pad so the engine needs to be that much back for the carb to be level. so, as i said the pinion will need to be 3 up. i'd just like to get in the ballpark because i know there is no universal number for what i'm looking for.
all good stuff no doubt. i have a level (a few actually) and brackets, and i know (or think i know) how and were to set the pinion angle. that's not my issue as far as i know.
It's become a mental roadblock for you. I get it, but you are overthinking it. What if it's off 2-5 degrees from optimum? You will probably run it or tweak it a bit. What if it's 10? You may have to do a bit more work. That probably means filing out the hole in the frame bracket for the radius rod and welding up the other edge. Or worse, weld up the hole and drill a new one. If the bracket is tacked, break the tacks and space it down or grind it to move the hole up. The bracket is not stressed much until power is applied. I took geometry in jr and high, but I'd rely on asking online to determine the angles and change over a 100 inch wheelbase with a pinion height of X and an engine angle of Y and still not believe it until the thing was in front of me and I could measure. Also as we have discussed, when is that magic 3 degrees measured? Empty and dry or with a full tank and two people? The pinion will only sink (not change angle) the amount the tire sags under the weight, but the back of the car will drop, changing the engine/trans angle. Best guess and fit stuff up. Otherwise, buy the frame plans and follow directions or buy a built frame and live with what you've got or fix it after it's ***embled same as your home built frame.
I would set it up at the desired 3 degrees but just make sure your radius rods have enough adjustment to make necessary degree changes... after all, that is how you set/adjust castor on the front axle
Okay, let's say the back of the trans is angled down 3 degrees and is at the same height as the pinion from the ground. (Most Ts have rake, so this is just a hypothetical case). You have a 36 inch long arm connected to the axle, which will change the pinion if moved up or down. How much? AI answer Useful Rule of Thumb For small changes like this, you can use the 1-in-60 rule often utilized in machining and fabrication. This rule states that a 1-inch rise over a 60-inch length creates an angle of roughly 1 degree. For a 36 inch bar For a 1-degree angle, the tip will be offset by just under 5/8 inch (0.625" is exactly 5/8, making 0.60" a very close approximation). For a 2-degree angle, the tip will be offset by 1 3/16 inches (1.20 inches).
interesting and i never heard of that rule before. ia is cancer as far as i'm concerned but this leads me down a rabbit hole i look forward to. thanks!
hey all i really appreciate everyone's comments. while i'm no newbie to cars actual building is way new and a bunch of this i just have to wrap my head around and understand. plus, the saying "you don't know what you don't know" rings in my head. bear in mind like anyone i don't want to do more work than needed and i don't want to ruin parts i don't have to; i don't have much fab skills or money. that said i understand mistakes are how you learn.
i looked for this my self and the only thing that came up for me were references to aviation. i have a couple of friends who fly so i should ask them.
a bit of an update: i'm taking another stab at doing it the more conventional way as it seems the more reliable way to get that pinion where it needs to be. meaning i'll be compressing the spring on the ch***is at approximately full weight then offering up the axle. as you can see from the picture working on the ground/dirt even after making great pains to make it level is a challenge to work from. made harder with the means i have of shimming things to get not only level but the height i need. jack stands work in many cases but i l also need more broad surfaces and that's where the blocks come in. anyway, i was out there yesterday and may be having success. took a long time to do it chasing around the mystery why the spring seemed longer laterally and vertically on one side and then changing when i play around with things. did a lot of talking to my self! i was so sure everything on the work surface was level and even side to side... clearly not but the trick was to find out how (i checked my work surface more times than i can count) so starting over from scratch was a good thing afterall.
btw this is an old photo not the current situ. you will note that the eye clearly sees the left side is higher than the rear. ch***is is dead on level. however, for some reason i could not discover this from my measuring... for some reason! also, it's not so easy to simply stand back and look at it; this picture was taken through the bunch of trees directly (like 5 feet) behind.
I hope this at least gets you in the ballpark. I've been there where overthinking things can lock you up. @Tim_with_a_T snapped me out of fibergl*** freeze on mine. I was considering a half dozen approaches to something that in the end was just do it. Best I can suggest is set it up level, get the rear axle located properly side to side and perpendicular to centerline and tack both the radius rod and spring mounts in with a slight upward pinion angle. The rear spring won't be holding up much weight and the shackles won't be at that 45, but so long as the tacks can hold the spring and the weight, you should be able to mock up the rest of the car. Just read your latest post. I think that spring is what is causing you all the grief. It partly locates the axle, sets height/supports the weight and also spreads when loaded. They store a lot of energy when compressed to ride height, and that is either by spreading the ends or pushing on the top mount and the ends. The former is not great unless it's really secure, the latter blocks positioning the crossmember properly. If this was coils or coilovers, you just cut a piece of tubing and set things in place. A parallel leaf, the spring pads set pinion angle and the u-bolts will hold things until you are ready to weld. You are trying to set things up with a big wobble in the middle on uneven ground! I think you need to resign yourself to the best guess and tack, then move on, knowing it can't be perfect. Futzing with sandbags and jackstands with shims won't get it exact where you are. I hope that the final weld isn't out in the woods with a generator and a stick box, but if it is, just do the best you can.
Those transverse leafs tend to take a set where one side of the car is higher. YT Paul Shinn, says you can get in and out of a Model A out the p***enger side and it will straighten up after a few times if you have been just one person and climbing in and out of the driver's side. Iron Trap has talked about it too. They set up one car with the full spring pack, then removed leafs to set ride height and comfort. They did have the luxury of the spring, shackles and mounts at the right widths (stock) to work together.
@RodStRace i don't think i was overthinking in this case anyway. although i can get get bogged down in that regard. i simply want to get it right and safe. you did touch on something in the back of my mind which is "i hope my tacks hold!". fwiw i have about 200 lbs. resting where the body will be which i figure will get me close enough. i will be using a stick welder for the tacks, was gonna run a looong extension cord out there but since then i think i'll just bring the rear over to the building; with axles and drums removed it may be less of a pita to hand truck it back and forth. wanna remove the center section but the gasket seal is fightin me and i have other fish to fry. my old man back tells me which battles to fight. i'm more optimistic than i was a week ago. i know i'll get it but my goal is to get the rear brackets before it's too cold to work. my original goal this season was to have a roller so the closer i can get the better.
Generally speaking, and there are many variables here, starting from a bare frame you want to do the following: Check your work surface and note any major variation from level etc. Set up frame on jack stands, level side to side. Set front of frame at approximate ride height using front tire height to estimate centerline height of front axle. Set rear of frame at approximate ride height using rear tire height to estimate centerline height of rear axle. To estimate ride height with suspension loaded on a leaf spring car, dis***emble the spring (carefully - lots of stored energy in the spring pack). Use the main leaf and spacers to simulate the thickness of the remaining leaves you removed. Bolt main leaf to crossmember and square it to frame centerline. Use the leaf spring bolt in each crossmember to triangulate and square the spring. Once you have your main leaf bolted in @ front and rear, you can ***emble the shackles and spring perches etc to approximate the location of your front and rear axles. Now you can center up and square your front and rear axles, by triangulating off the same leaf spring bolt hole to keep your measurements consistent. Be sure to either center the pumpkin or center the pinion (personal preference). Be sure to double check wheelbase side to side after triangulating measurements to locate axle placement. What springs are you using? If using early Ford original, match the dimensions to the axle ***embly they originally came out of. If using Speedway, for example, their high arch rear spring, they have an instruction sheet to estimate spring perch width vs weight over the axle. You also need to be concerned with axle width, if you are going to narrow the axle, make sure you still have room for the spring perches, etc. All of this is a consensus of compromise, just do your best to make it as close to optimal as your packaging and design constraints will allow. After you have all this figured out, you can estimate drivetrain placement. If you don't have an engine and trans to use as mock up, it is a lot more difficult. Best to use mock ups if you can. With frame at estimated ride height and rake, set engine so carburetor pad is level. With carburetor pad level, block oil pan to lock angle. Bolt trans to engine, measure angle at output shaft. Set pinion angle equal to but opposite of trans. For example, if trans is pointed 3* down, pinion goes 3* up. Don't get stuck on "pinion has to be 3*". It's more important to have ride height, ch***is rake, carb leveled, THEN let that dictate pinion angle. In general, this is how you go about it. Tack your stuff, take a bunch of measurements, take pictures to make sure you like it. Adjust as needed.
hey all. i just got back in from my suspension escapades and i can report some success. a breakthrough yesterday and after a bit of a strange setback today i got it sorted. gotta clean the areas to be welded and go from there... after the weekend of rain that is. i'm a bit tired and gotta get me some dinner but wanted to thank y'all for your perspective. pretty sure i just jinxed myself.
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