2000 replies to this topic

[RexKrazy]

...then cut the flange away w/a hacksaw:



Done!


Here's the modified 1/3g lhs mount (on the left) compared w/an unmodified oem one...also shown is the piece cut out of the flange:


Getting closer!

Cheers!

I would not recomend this mod. I had a mount that was cut like this break on me.....not a fun experience. I put a stock mount in w/ a notch in the timing cover and it is fine. Maybe you could cut the mount if you add some other support to it also (without melting the rubber).

Anyways, nice build though. Just thought I'd share that experience.

[kakabox]

I would not recomend this mod. I had a mount that was cut like this break on me.....not a fun experience. I put a stock mount in w/ a notch in the timing cover and it is fine. Maybe you could cut the mount if you add some other support to it also (without melting the rubber).

Anyways, nice build though. Just thought I'd share that experience.

I'm sorry for your experience. Do you have pics of the broken mount?

Did the internal rubber biscuit fail first? The rubber is the 'fuse' in the mount, at least for the torsional loading (twisting due to eng accel/decel). It will fail long before the steel shell will. I'm surprised you didn't notice the failed rubber section first, or did it fail all at once? Did the mount fail at the modified gusset...from a crack propogating from the mod?

Did you filled the mount w/urethane and/or leave a 'notch' or saw cut in the gusset when you removed it? Perhaps a fatigue crack grew from there. Even then, the stock mount should have enough residual strength (area) left due to the two additional gussets to allow you time to notice a failing mount:

You didn't remove the additional gussets, did you? I'd like to see how you modified the oem mount.

Was the oem mount that you modified in good condition to begin w/? Were all the factory welds intact and not cracked. Was the rubber biscuit intact and not cracked out? Was the bolt that connects the engine to the mount damaged? Were all the mount bolts properly torqued?

I suspect the failure of the mount was due to improper clearancing of the mount and/or using a previously damagaged mount to begin with. IMO, with the mount gusset properly radiused, as I show, there should be no detrimental loss of strength or durability when using a oem rubber bushed mount in good condition.

There may be a fatigue issue w/mounts that have had the gusset improperly clearanced (sharp cuts or notches, left behind from clearancing, not smoothed out or radiused) or have had too much material removed and/or are damaged (cracked welds) to begin with.

[DarkHand]

My guess would be a crack propagating from the modification too, either from a cut that went a bit too far, or even too sharp of an angle in a good cut. Kaka's rounded cut hopefully eliminates any of those issues. This mods been done since the 80's to fit browntops into our cars... Not saying they're failsafe but they've been pretty well time-tested.

Edited by DarkHand, 11 October 2007 - 02:09 PM.

[lxndr]

Just to add my $.02,

Any sharp corners, edges or burs are a breeding ground for stress fractures, the large radius in Kaka's modified mount should eliminate any potential failure.

Also, I can vouch that the rubber will fail first as indicated in this picture:

I was going to just use the engine mount from lxndr's drivetrain I bought; it was already trimmed for a D16...but, I guess he did one too many 6000 RPM clutch dumps...his mount was done!

Kaka' helped me drop this motor in my CRX and neither of us noticed any obvious wear on the modified motor mount shown above before installation.

Edited by lxndr, 11 October 2007 - 02:59 PM.

[kakabox]

My guess would be a crack propagating from the modification too, either from a cut that went a bit too far, or even too sharp of an angle in a good cut. Kaka's rounded cut hopefully eliminates any of those issues. This mods been done since the 80's to fit browntops into our cars... Not saying they're failsafe but they've been pretty well time-tested.

Without seeing the failed mount, or knowing it's service history, I can only guess at the cause of the failure.

I haven't run the numbers (yet), but it's my opinion that the factory mounts are overdesigned for the loads they see w/D16 swaps. If a factory mount is in good condition before modification (rubber biscuit intact, welds solid, no obvious damage to the steel shell), it's my opinion that clearancing it per my build thread instructions will cause no detrimental effects to the ultimate and fatigue strength.

As always, your milage may vary! But as you point out, they have been in service for sometime now. This is the first failure I've every heard of.

[RexKrazy]

it was modified very much like the one you have done. I didn't do it, and I don' t remember for sure. but i believe they had basically just hacked the conflicting gusset right off. I don't think it really created a stress riser for crack propagation, I think it just dramatically decreased the torsional stiffness and the steel fatigued.

the rubber did not fail, nor did the shell, just the support bracket. it basically just ripped the bracket off of the shell. Leaving a significant piece of the gusset on there with a nice radius on the corner like you did will certainly be much better than mine was.

is there room to add another gusset on the underside?

Edited by RexKrazy, 11 October 2007 - 03:46 PM.

[kakabox]

it was modified very much like the one you have done. I didn't do it, and I don' t remember for sure. but i believe they had basically just hacked the conflicting gusset right off. I don't think it really created a stress riser for crack propagation, I think it just dramatically decreased the torsional stiffness and the steel fatigued.

the rubber did not fail, nor did the shell, just the support bracket. it basically just ripped the bracket off of the shell. Leaving a significant piece of the gusset on there with a nice radius on the corner like you did will certainly be much better than mine was.

is there room to add another gusset on the underside?

Steel (or any other metal that I know of) cannot "fatigue" w/o a stress riser present and a crack/s formed. Structures fail in fatigue due to cyclic loading causing existing stress risers to form cracks which then propagate over time until the stress due to loading exceeds the strength of the remaining section area. How quickly this happens is due to many parameters, the main ones being how big a stress concentration (Kt) there is, the magnitude and frequency of cyclic loads and the material...but fatigue failure always involves a stress riser (and crack) of some kind. Even if you can't see one w/the naked eye, they are there, hence, for fatigue life, surface finish and corner radii are very important.

I can't really see a torsional failure w/o the rubber failing first. That would mean either the torsional stiffness of the rubber exceeded what was left of the steel bracket (after the hack job), in other words, the load twisted the steel bracket instead of the rubber insert. Or the mounting bolt bottomed out in the shell...like the screwdriver in this pic:

...and twisted the shell off. I just can't see it physically possible for the mount bolt to deflect that much, unless there was something else going on besides the alterted mount. Like maybe a failed or disconnected rear center mount, or cracked/damaged welds on the mount. Or maybe loose mounting bolts...?

I would think a "dramatic" loss of torsional stiffness in the steel support bracket would of been noticable and able to be felt. Look at the pic above again...that's a torsional load applied to the mount. Are you saying that the remaining steel bracket's torsional stiffness was less than the rubber? If that was the case, I would think you would be able see and feel that long before you experienced mount failure.

There appears to be room on the underside to weld on another gusset. However, careless welding of a gusset might create other issues. Like melting the rubber insert and/or causing a heat affected zone that could be a stress riser too.

IMO, an additional gusset is not needed if the mount is clearanced "properly".

[kakabox]

Battery Relocation, Rev. A.

After relocating the Kakabox's battery to behind the passenger seat (what passenger seat? !)...you guys gave some excellent suggestions, like adding a fuse to the positive cable and running a negative cable to the engine.

The car seemed to run perfect the way I wired the battery...however, I considered the feedback I got and did a little more research.

I found an article I cut out of a car mag a couple of years ago about car wiring, specifically about grounds. The article is by Ron Francis ( http://www.ronfrancis.com/ ). He wrote that 80-90% of the "tech help" calls to his shop about automobile electrical issues are caused by bad or incomplete grounds. He wrote this article of grounding tips and facts to educate people in hopes of reducing the number of calls.

The number one re-occurring theme of the article is that... "the primary ground connection for the battery is the engine block using a copper cable. It's ok to use the frame (chassis), but only as a back-up grounding system."

Ok, so what did I do? I grounded the battery to the chassis. Seems to work just fine, however, I found the following quotes from Ron interesting and enlightening:

"...copper is the best conductor used in an automobile, ...100% conductivity. Steel is far worse, at only 12 to 16% percent conductivity when compared to copper!"
"You can never have enough grounds"
"Any wiring job will last one to two years before the bad grounds take over."

Well, that last quote got me thinking and I decided to stop being lazy and stubborn and revise the wiring.

So, along with running a 2 gage copper cable to the engine, or, in this case, to the OEM battery ground point on the transaxle, I put a fuse in the positive battery cable (and I didn't have to alter my existing pos cable run!). FWIW, the ~9' run of #2 negative cable added 2.5 lbs. to the car.

Ok, I'll shut up now, and let the pics do the talking!










Cheers!

[RexKrazy]

Steel (or any other metal that I know of) cannot "fatigue" w/o a stress riser present and a crack/s formed. Structures fail in fatigue due to cyclic loading causing existing stress risers to form cracks which then propagate over time until the stress due to loading exceeds the strength of the remaining section area. How quickly this happens is due to many parameters, the main ones being how big a stress concentration (Kt) there is, the magnitude and frequency of cyclic loads and the material...but fatigue failure always involves a stress riser (and crack) of some kind. Even if you can't see one w/the naked eye, they are there, hence, for fatigue life, surface finish and corner radii are very important.

I can't really see a torsional failure w/o the rubber failing first. That would mean either the torsional stiffness of the rubber exceeded what was left of the steel bracket (after the hack job), in other words, the load twisted the steel bracket instead of the rubber insert. Or the mounting bolt bottomed out in the shell...like the screwdriver in this pic:

...and twisted the shell off. I just can't see it physically possible for the mount bolt to deflect that much, unless there was something else going on besides the alterted mount. Like maybe a failed or disconnected rear center mount, or cracked/damaged welds on the mount. Or maybe loose mounting bolts...?

I would think a "dramatic" loss of torsional stiffness in the steel support bracket would of been noticable and able to be felt. Look at the pic above again...that's a torsional load applied to the mount. Are you saying that the remaining steel bracket's torsional stiffness was less than the rubber? If that was the case, I would think you would be able see and feel that long before you experienced mount failure.

There appears to be room on the underside to weld on another gusset. However, careless welding of a gusset might create other issues. Like melting the rubber insert and/or causing a heat affected zone that could be a stress riser too.

IMO, an additional gusset is not needed if the mount is clearanced "properly".

I was worried you'd say that. I was just trying to say that the process of cutting the gusset did not produce a stress riser, because the gusset isn't even attached at the point of failure...hope that's somewhat clear.

[koshir]

Battery Relocation – Rev. A.
After relocating the Kakabox’s battery to behind the passenger seat (what passenger seat? !)...you guys gave some excellent suggestions, like adding a fuse to the positive cable and running a negative cable to the engine.

Now it's perfect !!!
I'm glad you did that cuase before it was good but not 100% perfect !
One way now that you have ground on engine is that you conect all those ground on engine with wire if you didn't do that already, in that case all engine is directlly wired to battery that is the best thing you can do !
Once again great build...this is trully inspiration if my crx will go at least 50% in your way I'll be more than happy with it !

take care

[Screech]

That looks great.

[dkyk25]

wow!
i'm speechless. it is one thing to do a kickass work on your car, but totally another to document it for others to benefit.
i know it's a great hassle taking pics while working but you did an awsome job to capture what's important.

without a question, this build and you are one of the most valuable asset to this community.
great work and thanks for showing it to us!

[kakabox]

Last AX of the Season Pics:

http://autocrossplus..._246418#photo_s
http://autocrossplus..._246520#photo_s
http://autocrossplus..._246623#photo_s
http://autocrossplus...ctice/img_23176
http://autocrossplus...g_23188#photo_s
http://autocrossplus..._231910#photo_s
http://autocrossplus...ctice/img_24022

I have been very pleased w/the performance of the Kakabox this season. The car has proven to be faster than I thought it would be...it's still faster than the driver (me). More seat time next year will correct that!

This winter's Kakabox projects include (I'll post per usual as I complete them):
Chassis mounted tubular adjustable rear stabar (similar to jsgprod's design)
TEIN suspension installation...? (if it comes this winter...?)
Installation of firstgencrx's cc plates along w/revised Kakabox stb

Cheers!

[Maine_Honda_Racer]

Sounds like some good plans. I wonder if you ever plan to take this on a more than just the local auto-cross club level........it certainly seems like you have the skills and prepartion for it.

[zakats]

ooh me too ^^ can I use my escort wagon??

...but I want kaka to build another car for us all to marvel at!