I'm using a stock rebuilt 31 motor, 39 trans, lowered stock axles/suspension front and rear, skinny tires. I've stepped the rear of the frame to get the car a little lower. While doing that decided, I should box the rear for safety. While doing that decided, to weld the crossmembers in and fully box the frame. I know that all of this is unnecessary considering the lack of power this thing has but, in the end, will only add about 30lbs of extra weight so I feels it's worth it. Anyway, before I finish boxing, I was giving some thought to adding a K member. I guess my question is, with a boxed Model A frame, do I need a K member or the like to "finish" the frame. In other words, regardless of engine choice, does road force warrant it? or will the lack of one, cause cracks to be where the frame once flexed now that it is rigid? I'm probably making this more complicated than it needs to be. I'm interested in opinions anyway. .
I'm in the same boat! Getting ready to "build" (read modify) an A frame for my Tudor. Keeping an eye on this one!
I added a simple K-member to the frame on my Model A Tudor a few years back. A round tube between the rails and a couple of tubing pieces attached near the middle of the first and angled outward toward the front. I needed something to hang the exhaust from anyway... Here is my favorite k-member in a model A frame..
I plan on using my original pedal location. My new master cylinder will probably go on the opposite side mounted on the front of the center crossmember. I'd like to keep from reinventing the wheel. I was thinking something like this. Thoughts? Sorry for the crude sketch.
I'd like more info on that 39 trans bolted to the Banger motor. Then what your doing with Torque Tube being the A won't bolt to a 39 Box and a V-8 rear end is to long for the Model A. The Wizzard
Are you saying the A torque tube won't bolt up? I wasn't aware of that. This is my first time with this stuff. I was going to use Clings V8 trans kit. Allows you to use all of your stock pedals and emergency brake. It's expensive but looks like quality. American made too. I e-mailed them a couple months back and I had the impression, it was bolt in. Meaning, using the torque tube without modification.
A Model A frame is not very rigid; it was designed to flex without damage in ordinary use. A K-member helps keep the frame from racking (i.e. turning into a diamond-shape instead of a rectangle) and helps keep the frame from twisting. Boxing increases the vertical load capacity of the rails and helps prevent frame twisting. As Walls observes, boxing or adding a K-member to an A frame may be counter-productive in that they require other parts of the frame (like where the crossmembers connect to the rails) and suspension to accommodate the stresses that used to be more widely distributed in an A frame. An elaborate K-member and full boxing seems like overkill for the banger, but I'd definitely box the area around the step in the rear of the frame, and use limited boxing if a new crossmember is needed for the '39 trans. And make sure the stock crossmembers and their rivets are undamaged.
Side by side the Model A trans and the 39 trans aren't even close. Although they did use the 4 banger through 1940 but the side mounts went away. The clam shells for A and V-8 are different. Here's a shot of my A-V8 conversion with no Boxing. Boxing is WAY overrated unless your making big horsepower. I'm creeping up on 70 and have been doing this since High School. I have yet to see an A ch***is racked or twisted with a Banger or Flathead V-8. I put boxing right up there with Air Bags, pretty much unnecessary. The Wizzard
Here's something else to think about. If you fully box the frame how are you going to do your bellhousing side mounts? If you leave a void for mount holes you will move all (if there's any) frame flex to that point. What do you think will happen next? The Wizzard
About the clamshells, I'm going to have to check into that. I ***umed it was not an issue. I'll let you know once I find out. I had a roadster that had a 283 -boxed frame but no added X member. The doors would occasionally open on corners and you'd pinch your arms sometimes resting them on top where the door met the body. So, I hear you on the crossmember. I also had a Vicky. It really was a rickety little beast. Stock frame.Squeaks and moans while taking corners and hitting bumps. Maybe some of that was worn suspension? Who knows. I do know, since I stepped the rear, boxing is appropriate in that area. From all that I've read, selective boxing on a frame which is held together with rivets and was designed to flex will put undo stress in areas that it wasn't intended. So for me, complete boxing, is what I've decided to do. I'll inset the plate from center to front crossmember a half inch so it doesn't look so ugly. I still intend to use the stock rear mounts which are rubber mounted. I'll have to cut/ shorten them for the width taken away from the boxing. so the trans will be "floating" like the original one was. I know these types of discussions are usually very subjective. I know I haven't seen any other threads on this website talking about beefing up a frame for a banger motor. Maybe I'm just looking to make extra work for myself
With a banger in there you probably wouldn't ever need it, but since you are boxing the frame anyway it sure won't hurt at all to add a K or X member to stiffen things up a bit. When I did my A frame years ago I knew I couldn't have any twist in it as I am running a gl*** 27 body and gl*** doesn't like to twist at all. So I built in a center crossmember and then added legs to each side. It evidently worked because nothing has ever moved or cracked. Don
Boxing the Model A frame is a good thing. Boxing the frame and adding a k-member will help eliminate frame flex and enable the suspension to do it's job. The elimination of frame flex will also help to keep the doors from coming open when encountering bumps and going around corners. Making the frame rigid will also eliminate cracks due to work hardening of the metal due to flex. Utilizing the existing center crossmember in your k-member design will prolly get you the biggest bang for your buck. I've seen some that have been modified to be a k-member, and others that have been modified to be an x-member. Both work well...
Cling said use the V8 clamshell. No other parts to buy. I'm going to order one hopefully next month. I started rebuilding my transmission a couple months ago. Kinda forgot about it until recently. Been trying to concentrate on my frame.
A boxed frame rail resembles a rectangular tube, in terms of torsion-twist and bending resistance. It is effort that repays in far less body movement, doors that pop open and paint-bodywork preservation.
I decided to build my own frame and use a k-member from SoCal speed shop. . Posted from the TJJ App for iPhone & iPad
Yes, clamshell is only needed adaptation for torque tube. Look at U joint...early A looks like it was made from an Erector set, late A and all V8 use forged parts. Guess which you want... After boxing look at front and rear crossmembers...not much resistance to twisting or racking there, a good argument for a K or X to triangulate things! The K member idea gives you a choice of mounts, A rear mount or one of several V8 types, but sounds like you are keeping the A bellhousing there which eliminates need to buils a belly band or go to '32 type wi$hbone and so simplifies yor life... I would construct new crossmember with extension to tie into the original piece as suggested, and consider buildin it to take a '39 or a '40-48 type pedal ***embly. These can be simply bolted tio the flat vertical part of a K or the K/X left side leg can be built to pick up the late pedal mount completely.
Its easy to add the K or the X now. If you ever decide to drop a more robust power plant into the car, you'll be ready to go.
And as part of that...add in the mounts for the '39 trans (***uming here the "more robust" doesn't mean an L-88...) and just leave out the pads since you are currently using the bellhousing mounts.
One point and one question: If you hit a bump with an unboxed, un-K'd Model A frame, the resulting energy is dissipated in the tire, spring, shock, wishbone, crossmembers, and rails. If you strengthen the rails by boxing and K'ing, that leaves more energy for the other components to dissipate. The result is more stress at the un-reinforced points, particularly where the crossmembers attach to the rails. Question: The stories about doors flying open - how much of that problem attributable to flex in the body as it rolls in response to a curve?
I'm ***uming the flathead and banger aren't a direct swap in a Model A as far as firewall clearance, distance to the radiator, etc.. If I were to make mounts for the 39 trans, they wouldn't be in the right spot for an engine swap anyway. Again, I'm ***uming that. If you or someone knows for certain, or has an idea on that, I'd be interested to hear it.
The Jalopy Journal
