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Rather than Bellcranks, multiple coilover mounts?
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Author:  CodySimonson [ February 2, 2018, 10:29 pm ]
Post subject:  Rather than Bellcranks, multiple coilover mounts?

So I've pretty much decided Bellcranks won't work well with the coilovers I'm choosing so I was thinking, what if I had 3 different upper coilover mount points to adjust effective spring rate.

Has anyone tried this and did it work ok?

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Author:  davew [ February 3, 2018, 9:06 am ]
Post subject:  Re: Rather than Bellcranks, multiple coilover mounts?

Search Velocette. They used a slotted arch design on the rear shock attachment as a way of adjust shock and spring load. You could probably modify a dirt track rear trailing arm multi-hole bracket with the hole already in a radius pattern to fit your needs. Dave W

Author:  horizenjob [ February 4, 2018, 12:25 pm ]
Post subject:  Re: Rather than Bellcranks, multiple coilover mounts?

Sure it should work and give you a benefit of a strong mount. I think it comes down to what you choose for angles. In your picture the wheel is at full droop, what will the axle be at full bump? My formula car has the front shocks a bit more than 45 degrees, If I remember correctly.

You would probably be just fine with the stiffer setting though. If they are really too stiff I don't know if you can get enough difference to solve that problem.

Author:  geek49203 [ February 4, 2018, 3:54 pm ]
Post subject:  Re: Rather than Bellcranks, multiple coilover mounts?

davew wrote:
Search Velocette. They used a slotted arch design on the rear shock attachment as a way of adjust shock and spring load. You could probably modify a dirt track rear trailing arm multi-hole bracket with the hole already in a radius pattern to fit your needs. Dave W


and I've got a spare set of those I'd let go really cheap. Used 'em for my own front mounts of the rear trailing arms.

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Author:  Driven5 [ February 6, 2018, 3:18 pm ]
Post subject:  Re: Rather than Bellcranks, multiple coilover mounts?

Bellcranks and multiple coilover mounts don't inherently do all of the same things. So what problem are you actually trying to solve with this?

Author:  Bent Wrench [ February 7, 2018, 5:06 pm ]
Post subject:  Re: Rather than Bellcranks, multiple coilover mounts?

In that drawing Cody posted the shock is laid over at too much angle.

In practice you want the shock as close to perpendicular to the motion as possible. Some angle is good as you don't want body roll to put the shock motion over center.

Otherwise shock damping and spring rate is compromised.

With the shocks angled so severely, travel will be reduced and higher damping rates will be needed.
In other words the wheel will have a mechanical advantage over the shock so stiffer shock damping will be needed.
A similar effect will be in place for the spring rates since the wheel moves farther than the spring is compressed.
Another effect that comes into play is the rate increases as the angle decreases to perpendicular.
The spring rate at the wheel increases as the suspension is compressed, so the higher rate spring needed to support the chassis at that angle the wheel rate increases as it is compressed.
In shock damping related considerations extremely stiff shock damping will be needed and the shock will have less control over small movements.

The rising rate motion ratio is used in cars with lots of aero downforce to limit suspension travel at higher loads.
If you are following the progress of the Pink Panther MG, You will note that he has removed the bellcrank setup he had in the front.

Many dirt car setups will separate the shock from the spring so they can do a linear spring rate and a progressive shock rate using angles

Author:  davew [ February 8, 2018, 8:10 am ]
Post subject:  Re: Rather than Bellcranks, multiple coilover mounts?

I think that the original design concept was to be able to change the shock angle so you could increase/decrease the spring rate and damping. Not the best functional design but a lot easier to fab then a bell-crank suspension. Dave W

Author:  horizenjob [ February 8, 2018, 1:54 pm ]
Post subject:  Re: Rather than Bellcranks, multiple coilover mounts?

Quote:
In that drawing Cody posted the shock is laid over at too much angle.


People keep hammering on this subject of coilover angle and I think it's made out to be more of a concern than it should be. Yes it has the effects mentioned, but that just isn't the whole picture. I think the engineer's expression "Perfect is the enemy of good enough!" applies here. I think the angle on my antique 1978 Formula Ford is at least 45 and probably 50 degrees. My car qualified on the front row for the national championships the year it was made and the other cars at front were the same model. People moved to setups with bell cranks and pushrods and lots o'bearings because of aero reasons. The other benefits were nice to have, but aero is why people spent the money and effort.

The great majority of builders on this site would be better served by accepting a compromise on shock angle as opposed to the effort to go to an inboard setup. Let's look at some drawbacks... They can take a lot of effort to design well, most that I see introduce plenty of their own compromises. If your setup accumulates maybe 1/16" of deflection in the mounts - that could be half the stiffness of a well designed frame. That 1/16" of deflection would be spread around all 4 corners and is not an easy standard to meet. It will cost more by adding several more bearings per corner and a radius rod. Often the shocks are located higher up raising your CG and also are not not in a good airflow, so they will run much hotter.

I don't think anyone should feel bad or that they did not do a good job because they have coilovers externally mounted in the traditional manner. If you publish plans for our car, like Kurt, there is an added incentive because the effort he put into it is spread over the copies make of his design. I looked at this for awhile on Car9 and just opted not to do it. If you want shocks that are not out in the breeze, I strongly recommend buying bodywork from Jack McCornack!

edit: Just to be clear, I did not qualify for the National Championships! :rofl:

Author:  Driven5 [ February 8, 2018, 2:49 pm ]
Post subject:  Re: Rather than Bellcranks, multiple coilover mounts?

davew wrote:
I think that the original design concept was to be able to change the shock angle so you could increase/decrease the spring rate and damping.
That might be what the posted design concept is intended to accomplish, but that's not what a bellcrank design inherently does...Hence my confusion about the motivation behind equating two. And while I don't know enough dimensions to run any math on it, I am also somewhat skeptical of how much benefit/value this multi-mount design will ultimately provide.


horizenjob wrote:
Quote:
In that drawing Cody posted the shock is laid over at too much angle.

People keep hammering on this subject of coilover angle and I think it's made out to be more of a concern than it should be. Yes it has the effects mentioned, but that just isn't the whole picture. I think the engineer's expression "Perfect is the enemy of good enough!" applies here. I think the angle on my antique 1978 Formula Ford is at least 45 and probably 50 degrees. My car qualified on the front row for the national championships the year it was made and the other cars at front were the same model. People moved to setups with bell cranks and pushrods and lots o'bearings because of aero reasons. The other benefits were nice to have, but aero is why people spent the money and effort.
Just like bellcrank vs traditional mounts has nothing to do with fixed vs adjustable motion ratios, bellcrank vs traditional mounts also have nothing to do with rising rate vs falling rate. Stating that the coilover is at "too much of an angle" does not actually promote bellcranks over traditional mounts, as there is no reason that the traditional mounts can't also be positioned to put the coilovers at a more effective angle. I believe some builds here have even put some effort into doing so, to at least some degree or another.

Author:  KB58 [ February 8, 2018, 2:51 pm ]
Post subject:  Re: Rather than Bellcranks, multiple coilover mounts?

Agree with horizonjob and in my book I lay out the pluses and minuses of both approaches. I made Midlana #1 with a bell-crank setup because I know people think it's sexy and it'll help sell more books. I do note however, that if I was making just one car for myself with no plans, I'd probably go with outboard just for the simplicity. The book covers both setups and allows builders to choose. That said, at least one builder has come to the realization that going outboard is going to result in spring rates so high that he had some trouble finding suitable units.

Author:  nick47 [ February 9, 2018, 9:18 pm ]
Post subject:  Re: Rather than Bellcranks, multiple coilover mounts?

I made my shock mounts adjustable so I could change the angle if I wanted. 45K miles later, I've never changed the angle.

Author:  GonzoRacer [ February 19, 2018, 10:24 am ]
Post subject:  Re: Rather than Bellcranks, multiple coilover mounts?

nick47 wrote:
I made my shock mounts adjustable so I could change the angle if I wanted. 45K miles later, I've never changed the angle.
I made my shock mounts breakable so that I could change the angle when one of them broke... :BH:

:cheers:
JDK

Author:  carguy123 [ February 19, 2018, 12:54 pm ]
Post subject:  Re: Rather than Bellcranks, multiple coilover mounts?

GonzoRacer wrote:
I made my shock mounts breakable so that I could change the angle when one of them broke... :BH:

:cheers:
JDK


Now we know what happened to the engine too. :oops:

Smart thinking, now you can go tell the Missus that you just HAVE to have that super de dooper new engine.

Author:  GonzoRacer [ February 19, 2018, 4:39 pm ]
Post subject:  Re: Rather than Bellcranks, multiple coilover mounts?

carguy123 wrote:
Now we know what happened to the engine too. :oops:

Smart thinking, now you can go tell the Missus that you just HAVE to have that super de dooper new engine.
Nope, done used that one for the last engine. I'm gonna have to go with the "Act of God" defense this time... :mrgreen:

Author:  carguy123 [ February 19, 2018, 6:15 pm ]
Post subject:  Re: Rather than Bellcranks, multiple coilover mounts?

GonzoRacer wrote:
carguy123 wrote:
Now we know what happened to the engine too. :oops:

Smart thinking, now you can go tell the Missus that you just HAVE to have that super de dooper new engine.
Nope, done used that one for the last engine. I'm gonna have to go with the "Act of God" defense this time... :mrgreen:


You know, I'll bet this group can come up with a very creative way to help you out.

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