What about engines being cross-members, too?

I saw something one time about engines being used as structual components. Does anyone have any info on this?

 

Sure, early Bugatti cars of the 30's, and the block was Aluminum.
Shouldn't be a problem in compression loads, assuming you have an iron block. Tension and torsion are also present and need a bit of evaluation. Most engineers begin by modeling the frame as a network of "springs" and apply loads...this is related to physics, and the free body diagram method. Key here (for steel) is to not exceed the elastic limit load, (think: tensing an extention spring), also not to exceed a fatigue load where a frame corner (for example) experiences torsion from engine torque and tight road turns at speed.
For tension strength of grey cast iron, see: http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TGJ-4CVX5SN-4&_user=10&_coverDate=11%2F10%2F2004&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=7ac8744e4f9bbc01b49ab572d1347942

 

So it would work? HA HA!

 

Talk to your engineering friends...it is a most complex analysis. And you would need to know the actual "condition" of the engine block in question.

 

Not trying to be picky but the Bugatti crankcases and legs were aluminum, the removable blocks were cast iron. Modern sprint cars use motor plates that are somewhat of a crossmember. Vincent Black shadow motorcycles used the motor crankcase as a stressed member of the frame.

 

Remember that the engines that ARE used as structural members (think Ducati M/C) are designed to be used that way. It DOES make a difference.

I would not use a SBC or SBF as a structural member, if for no other reason than the thin-wall castings not being up to more stress.

But, yes, the concept has been and is being used in many applications, mostly motorcycles (CBX anyone??)

Cosmo

 

I think you may mean the cylinder jug/head were cast iron. The "crossmember" was the lower Aluminum portion if I recall correctly.
I got to restore a 27 roadster recently as part of a team. They were amazing cars, even w/their cable braking systems.

 

A lot of race cars use the engine as an integral part of the chassis. Think F1 and ALMS, not NASCAR.

 

My application is not a true representation of "the engine as a crossmember (stressed member") discussion. From a legitimate engineering perspective, its not in the right place, the engine bolts to a corresponding crossmember, and torsional loading issues are effectively eliminated through the use of a transverse spring. Certainly, my chassis has to deal with torsional loading from engine rotation, but the frame isn't seeing suspension loading at the corners.

My primary objective was to use the engine/transmission as an adjunct compression loading component. Well, that and the fact that I wanted a ridiculous lokking motor mount

 

Yes, the lower sump aluminum casting was in effect two crossmembers, upper crankcase had the crankshaft and the blind bore cast iron cylinder block attached to this, cam box on top of that.

 

DollaBill, You can't just post one photo of that project! Please post some more views.

 

Formula cars, sure, but a more mundane example might be the Model A. As with Dolla's car, transverse springing took out some problems, but effectively the engine's bellhousing was not just a crossmember but the anchor point of the front radius rod, the main locating member of the front suspension.
Model A engine was flexibly mounted in front (after earliest cars), but bellhousing was a near solid mount, isolated only by thin and tightly clamped sheets of rubber. Model A's with the Float-a-Motor conversion have all sorts of problems with overall looseness.

 

almost every proper race car (i.e. not nascar, but sports cars, irl, champ car, f1, etc.) uses the engine as a stressed member, this has been the case since the late sixties, early seventies, this goes for both specialty blocks and production blocks. the key is to make sure your mounts are all triangulated properly, so the frame nor the engine will be able to pivot around the mounts.

 

thanks to everyone. Once again I'm getting far more knowledge than I ever expected. A lot of stuff I didn't that I didn't know, so to speak. Please offer some more is anyone has it. All the arguments so far have been very good, and logical. My idea was a SBC as the engine/crossmember. Cast Iron was my thought. I'd like to hear more about triangulating the mounts. Even stick pictures would be great.

 

I'd also like to see more pictures of this project.

 

Eddie Hill around 1961 used 2 pontiac motors as part of the frame on his dragster. I do not have pics.

 

Not exactly Hotrod but just about any traditional agricultural/industrial tractor uses only the engine between the front axle support and the bellhouse/tranny//rear differential section. To change out a clutch requires "breaking" the tractor in two - separating the rear half from the engine to get at the clutch. The front axle mount/ radiator support is bolted to the front of engine.

'Wonder if any Hotrodders thought about attaching the front axle support right to the engine block like typical tractors do?.

Here's a Ford 8N tractor front engine plate /axle crossmember / radiator support.



If you know what the phrase: "Walking the ring gear" means, you can understand why this can get you killed. If it doesn't go all the way over, letting it drop on the front wheels can snap the axle off or even break the tractor in half at the bell - right where you sit...
Powerband

 

I would think it would transmit a lot of vibrations to the chassis though. Just like if you use solid motor mounts.

 

Old Ford tractors do not even have frames. The engine, trans and rear axle are it!!!!

 

I have a Ducati and can vouch for the engine being a stressed member, but it was designed that way. You can also feel everyting the engine is doing through the rest of the bike. I doubt I would try and use a regular SBC or SBF as a stressed member. Though I would not have a problem pretty solidly mounting it.

 

I was going to post the same thing. Really early Deere one cylinder & two cylinder tractors did the same thing. The engine was an integral part of the chassis. Actually they didn't use crossmembers in the sense we do but the concept is similar.

 

Ford 8N tractor flathead conversion; http://home.att.net/~jmsmith45/funk.htm may spark some additional ideas.

Alex.