LocostUSA.com

While it would be okay to grind down the one rib a bit, you won't know exactly where it needs to be until you've set the driveshaft angles on both ends. At this stage, there is no reason to grind anything. Section the tubing at the back and bottom, the width of the trans and taper cut each end. Lap the cut tube 3 inches on each end with a tube behind the cut tube.

Also need room for the engine and trans to rock from side to side on the mounts and room to pull it out which won't be so easy with a complete car.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

I wouldn't bother moving the engine 3/4" unless you need to. It would hardly effect the CG of the car. If the motor/transmission weigh %25 of the car and you move it one inch, it will move the CG 1/4" inch.

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Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.

If the engine, trans, flywheel,etc weigh about 400 lbs and the car weighs about 1400 lbs, a 0.75 inch shift moves the cg about 4 to 5 inches.

Weight to be shifted over total weight equals cg shift over distance weight is shifted.

Even so, it isn't worth making it hard to work on. Put a full size battery in the back if you must. Remember the famed originals had the drivetrain at least a foot or so further forward than the locosts being built today.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Unless I'm misreading, isn't that backwards?

I'm going from memory on this one but if the engine was 50% of the weight of the vehicle and you moved it 1" then the CG should move 50% of 1" right?

_________________
-Andrew
Build Log
Youtube

I'm going by this:
http://www.faa.gov/regulations_policies ... 083-1a.pdf

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Weight. Arm. Moment
1400. 50" 70000
-400lbs. 25" -10000 old engine position
400lbs. 26" 10400 engine moved aft. 1"
1400lbs. 70400

70400 ÷ 1400= 50.28"
I show it only moved about a quarter inch for one inch engine moving aft.

I can't duplicate how I came up with that number. The formula is correct though.

Yet another reason to give yourself plenty of space. It's just not worth it.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

I'm welding up a batch of engine and transmission mounts.

I have a couple things of note on the mount. Prepwork will make for better welds really strength because I seen some bird crap strained through a screen hold like no other. Second it is better if possible to spin the nut verse the bolt. Something like 80% of a dry torque spec is overcoming friction and there is added friction torquing a bolt over a nut. A wet or oiled torque spec is IIRC like 30% to 50% overcoming friction. I would probably over do it on a motor and trans mount but that is just me.

Can you give some more specifics on prepping and welds?

I'm happy for feedback on how to improve.

My stuff is often kinda ugly, but I'm pretty happy with penetration and porosity if I grind it clean.

Right.Right.Right.

So in brief, it probably isn't worth moving the engine an inch to fine tune CG, -particularly- if moving the engine is going to make it (or anything else) hard(er) to work on.

_________________
Locost builder and adventurer, and founder (but no longer owner) of Kinetic Vehicles

You want to have bare metal in the area you are welding. Knocking off any grime and mill scale will greatly improve your welds. Debur the cut ends also.

Yup, unless you are stick welding with 6010 or 6011 rods (which I doubt) most everything you weld should be really clean. MIG welding likes clean metal. TIG welding will insist upon clean metal. Do a good job of cleaning the materials up, and you will (should) be rewarded with better looking and stronger welds.

Cleaning may include wiping it down with a solvent (don't use chlorinated brake cleaner --> research phosgene) such as denatured alcohol, acetone, or lacquer thinner. You can also mechanically clean it. I'd hit the surfaces with a grinder with a flap wheel myself, but sandpaper or files will also work.

Another part of prep is to properly bevel the joints. In thin material like is often in use on a locost, there really isn't enough material thickness to need or want to do beveling. But get into thicker material (over 1/8" to 3/16") and you really should be doing something.

JustDreamin