2000 VD Engine Mount cracking

[Will Velkoff]

I have a 2000 VD F1600 and have had two occasions where the engine mount tube has cracked. I was wondering if any other racers out there using the HPD chassis kit has experienced this, and if any successful upgrades have been implemented.

My initial plan is to remake the engine mount tube structure out of thicker walled tubing. If anyone else is interested in one I could get a batch made together, let me know.

Thanks!

[EACIII]

If you take the corners slower Will you will put less load on them

Ed

[HazelNut]

the tubes behind the fuel cell? The ones that come together in a triangle union with a big threaded bung and studs for the upper engine mounts? I had this issue on a pinto 99 a long time ago. We added some gusset plates and additional tubes and crap like that to shore it up, but at the end of the day it seems like the most likely culprit was that the engine was improperly shimmed by the previous owner. Once I remeasured everything with the chassis/engine on a surface plate and made new shims it never had a cracking issue again.

Paul Reiffle also used to ad in additional upper mounts to work with a cast valve cover he had as well.

Quality isn't great but found some ancient pictures from back in those days

[DaveW]

...My initial plan is to remake the engine mount tube structure out of thicker walled tubing. If anyone else is interested in one I could get a batch made together, let me know...

Just looking at that piece, there are huge stress concentrations with all those welded attachment bosses sticking out. You may be better off adding gussets, etc. to get rid of the small radius inside corners where cracks start. Just making it out of thicker material may help, but, IMO, that's not the root cause of the problem.

[cjsmith]

As Dave mentioned, that design is asking a lot of some hollow tubing. Attached is how my 97 VD upper engine mount is designed. Mine has a 1/8" steel plate with 2 bosses to attache to the engine. A 1/4" aluminum truss plate to attach to ether end of the frame rails. I've had no issues with my support.

[EACIII]

I lot of FC cars tie into a cast rocker cover. The Bowman has special plates for that. But don't think that is legal in FF. If I recall it says something like "the rocker cover can only be used as a cover" So if you used it as an engine mount it would be in violation of the rule. Unless they have changed that over the years. Have not spent a night reading the FF rules in a few years.

[problemchild]

If it keeps cracking, as pointed out, there probably is an alignment issue, and some preload involved. While identifying and fixing the alignment issue is the ultimate goal, you then have two opposite directions to decide between. Either making the mount stronger, or making the mount have more adjustment when being installed, and/or more flex when on track (as on Chris's car). Unfortunately, not a lot of space to work with.

[Will Velkoff]

Thanks for the input. I have done a thorough job to make sure alignment is not the issue. Everything slips together nicely so I know I'm not preloading anything. The mount is made of surprisingly thin walled tubing, and like Dave W mentioned there are a lot of stress concentrations with the various tubing pieces welded to the main tube.

My plan is to remake it with thicker tube, and also add a section of plate for where the bolts go to the engine. Right now its just tubing welded to the main tube. Then fill in remaining free real estate with gusset plates. The other two pieces that stick off with the threaded holes are not used for anything so I can eliminate those as well to get rid of some unnecessary stress concentrations.

I'll post some pictures when it's done.

[DaveW]

Sounds like a good approach. Hopefully that'll get rid of the cracking.

[DaveW]

...My plan is to remake it with thicker tube, and also add a section of plate for where the bolts go to the engine. Right now its just tubing welded to the main tube. Then fill in remaining free real estate with gusset plates...

A suggestion, which you may already be planning: Make the gussets out of square or U-shaped tubing and align them so the legs of the U's are near parallel to the sides of the main and any other tubes they will attach to. This will keep the gussets from "oil-canning" the tubes. I.e., the gusset legs should weld tangentially to the tubes they're attached to.

[Messenger Racing]

I have just bought a kit for a second conversion - it has the same bracket as my original car (same as seen in these pics). I have seen one example of an aluminum billett mount that was very nicely built. When asked the person told me it was from their orignal kit - anybody else seen or know of a source for the aluminum mount?