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Tech Information => Steering - Suspension - Rear End => Topic started by: Skip Pipes on December 18, 2017, 09:03:12 PM



Title: Lakester Front Suspension
Post by: Skip Pipes on December 18, 2017, 09:03:12 PM
Iím targeting building a 280/290 mph car and I know Sethís Hammond latest Lakester is usually stable at speed. Sethís car he has a unique front suspension that I like. Additionally DLRA363 has a similar front suspension, picture attached.  Iím sure there are many ways to get the job done but Iíd like to see if anyone can contribute pictures of successful designs.

Skip Pipes


Title: Re: Lakester Front Suspension
Post by: Stainless1 on December 18, 2017, 10:02:19 PM
Timely for me to Skip... I'm sure you don't need a pic of our VW based front end... I am also looking to do something different.... mostly because the crash destroyed the VW parts. 
I am watching for pics with ya....  :cheers: 


Title: Re: Lakester Front Suspension
Post by: Sumner on December 19, 2017, 10:15:45 AM
(http://purplesagetradingpost.com/sumner/bvilleother/Suspension-1.jpg)

I have a few pictures of different types of suspension here...

http://purplesagetradingpost.com/sumner/bvilleother/bville%20other%20index.html

Sumner


Title: Re: Lakester Front Suspension
Post by: Rex Schimmer on December 19, 2017, 05:10:35 PM
Skip.
I think that the suspension on the Aussie lakester is a great way to go. It keeps the suspension parts mostly out of the wind and also it would be fairly easy to add wing shaped fairing around the axle, steering and suspension, which if you are planning to go 290 will be important. I have attached a pic of the front suspension on my son and myself's small lakester. Our challenge was to get every thing inside the body, not completely successful, had to make a couple of blisters to cover one of the links, but Duke has a plan to fix that for this year. Our body dia is 25 inches but where the suspension is it is only 13 inch dia. at the front and 18 inch dia. where the shocks mount. We ended up with a lot of parts but it works pretty well.  You do need a strong front axle, ours is a 1.50 x .125 wall 4130 inter tube and a 1.75 x .125 wall outer tube, 4130 material. Our front wheel loads are pretty light at 200 lbs/wheel.

Looking forward to watching your lakester build, I know it will be interesting and inovative. You planning to run your roadster engine?


Rex


Title: Re: Lakester Front Suspension
Post by: strmlr555 on December 19, 2017, 07:44:32 PM
I wonder if torsion bar suspension would be the ticket , i have an older silver crown sprint car with torsion and it is pretty nimble for the big alc injected small block 410 c.i.,
it is much better @IRP than the stallard chassis (traditional coil over type setup.) that usually wants to stand on the right rear after 5 or so laps.


Title: Re: Lakester Front Suspension
Post by: Skip Pipes on December 20, 2017, 01:49:51 AM
Sumner
Iíve spent many hours on your fine site combing technical inspiration.

Rex
Yep, using the Roadster Engine Combination.

strmir555
I know torsion bar cars as I spent 10 years wheeling dirt/pavement Midgets. Two home-built (parallel rear/cross torsion front, it was my design and a clone Bultler 4 coil) as well as an Edmunds lightweight dirt car.


Title: Re: Lakester Front Suspension
Post by: NathanStewart on December 22, 2017, 10:13:54 AM
Don't be coy.  We're shooting for 300.  :-D :wink:


Title: Re: Lakester Front Suspension
Post by: Rex Schimmer on December 22, 2017, 02:24:22 PM
Skip,
As I remember you are planning to run a flat bottom car, much easier to fab, so if you run suspension you will need to make sure that you run some good bump rubbers to keep the car off of the ground. I would think that you would want the front suspension stiffer than the rear and the rear should be somewhat soft to provide lots of compliance and traction. The good part of a flat bottom car is the ability to have some pretty good ground effects for down force. Some rake on the chassis, and a diffuser at the rear should provide some great down force without the drag penalty of wings. I know you are thinking about all of this in your design. With they hp of your engine combo 300 should be attainable but you will really need to pay attention to the aero.

Rex


Title: Re: Lakester Front Suspension
Post by: Skip Pipes on December 24, 2017, 01:33:20 PM
Hi Rex

Well you know me I canít help myself. The design has advanced to try and get as much aero as feasible. Parts and tubing have arrived, so watch for a build thread.

For the front, Iíve noodle over every form of torsion bar suspension and canít seem to get it compatible with the axle fairing. Therefore Iím just going to focus on the Seth Hammond concept and try to design a tuneable version.

Skip


Title: Re: Lakester Front Suspension
Post by: Rex Schimmer on December 24, 2017, 04:17:21 PM
Skip,
Both you and Nathan are pretty stout guys, are you considering a "slimmer" driver, cuts down on the frontal area.

I would bet that my boy, Duke, would drive it, he gets in our little lakester pretty easy. He will have his 200 mph license next year, and maybe a record. (we hope!)

Rex


Title: Re: Lakester Front Suspension
Post by: SPARKY on December 24, 2017, 09:39:24 PM
REX what are you thinking  :-D


Title: Re: Lakester Front Suspension
Post by: Skip Pipes on December 25, 2017, 11:43:16 AM
Rex,
Thatís ballast to get the CP behind the CG.  :-D
Skip


Title: Re: Lakester Front Suspension
Post by: SPARKY on December 25, 2017, 12:33:27 PM
Skip do you have a picture of Seth's frt. susp.?


Title: Re: Lakester Front Suspension
Post by: Rex Schimmer on December 25, 2017, 12:57:53 PM
Skip said: "Thatís ballast to get the CP behind the CG" That is great! Always thinking!!!

Rex


Title: Re: Lakester Front Suspension
Post by: Skip Pipes on December 25, 2017, 01:48:30 PM
Sparky
Itís a photo from Hot Rod Magazine. I'll try and post it.
Skip


Title: Re: Lakester Front Suspension
Post by: SPARKY on December 25, 2017, 01:59:06 PM
Thanks Skip, What do you think the watts linkage brings to the table over a track bar with as little of travel as this is going to have.  I think my slow mind just answered that question---the track bar is going to be so short it is gong to pull the axle, and induce steer; if the steering gear is mounted to the axle?

Also, given you experience with suspensions over the years, how would you compare Seth's suspension to the red car that Sumner posted?


Title: Re: Lakester Front Suspension
Post by: Skip Pipes on December 25, 2017, 07:41:12 PM
Sparky
These are just my opinions.

What I like about Sethís car is the effective spring ratio is acting very near the end of the axle. Therefore itís acting closer to the tire contact patch then a design using springs within the body. So the effective spring rate is closer to 90% which I believe provides better control in roll and lessens the potential for yaw. I experienced pitch/yaw/roll on my roadster until I made changes to the steering rack and moved the spring base outward toward the front axle ends. No more spin stickers.
 
The lessen is; I knew better when I designed the roadster but convinced myself the only thing it would do is pitch. When I changed to a cross spring the car became stable.

Watts Link
The watts link keeps the axle dead center in pitch, which I think is important at 300 mph. The above is why I think Sethís car is so stable at speed.

If we had an awesome, rock hard track than we could likely get away with a lot less wheel control as weíd likely only see pitch.

Skip


Title: Re: Lakester Front Suspension
Post by: Lemming Motors on January 05, 2018, 09:46:54 AM
I am just finalising my design (Gas Lakester) so am a true newbie - spending a lot of time reading forum pages. In terms of Watts linkage etc., given the chassis width restrictions (assuming the components are inboard), has anyone utilised a sliding block set-up - the easiest way to reference this is a search for the Alfa Romeo GTA rear end. Sorry, I cant figure out how to include a snip in a post.

It allows vertical movement but should strictly control lateral movement and single wheel bump is simply the locating 'pin' swivelling in the 'block'. It would be high maintenance (lubrication etc.) in a road car but for a few hundred salty miles a year ....

I'd be interested in why this is a bad idea (or better yet a good idea) as its currently my proposed set-up on a straight front axle.

John





Title: Re: Lakester Front Suspension
Post by: Stainless1 on January 05, 2018, 11:09:37 AM
John, you can copy and past a link from your browser to send us to look at a picture or save picture on your computer, then use the additional options to post it.  Follow the options rules and give it a unique name....
 :cheers:


Title: Re: Lakester Front Suspension
Post by: Seldom Seen Slim on January 05, 2018, 11:29:00 AM
Another workaround is to take a screen shot of (whatever) and then post that.  It almost always works fine for me, and since the file name includes the date -- it's never "already used".


Title: Re: Lakester Front Suspension
Post by: Rex Schimmer on January 05, 2018, 01:36:18 PM
John,
Your "sliding block" idea will work and quite well. I discussed this type of lateral locating device with Mark Ortiz, the suspension expert for Racecar Engineering magazine, and he said that it has been used on sprint cars and midgets and quite successfully. As you have said it all gets down to making the parts so that they will slide vertically and easily. Easy to figure out the roll center and very compact.

Show us what you are doing.

Rex


Title: Re: Lakester Front Suspension
Post by: Sumner on January 05, 2018, 08:34:17 PM
I am just finalising my design (Gas Lakester) so am a true newbie - spending a lot of time reading forum pages. In terms of Watts linkage etc., given the chassis width restrictions (assuming the components are inboard), has anyone utilised a sliding block set-up - the easiest way to reference this is a search for the Alfa Romeo GTA rear end. Sorry, I cant figure out how to include a snip in a post.

It allows vertical movement but should strictly control lateral movement and single wheel bump is simply the locating 'pin' swivelling in the 'block'. It would be high maintenance (lubrication etc.) in a road car but for a few hundred salty miles a year ....

I'd be interested in why this is a bad idea (or better yet a good idea) as its currently my proposed set-up on a straight front axle.

John

(http://classicalfa.com/product_images/y/437/GTA150a__40797_zoom.jpg)

(http://classicalfa.com/product_images/m/375/GTA150__32743_zoom.jpg)
http://www.classicalfa.com/products/GTA150-GTA%7B47%7DGTAm-AUTODELTA-SLIDING-BLOCK-AXLE-LOCATOR.html

I can see how it locates the rear and lets it rise on the block and I'm guessing pivot around it but you still have the springs outboard unless they are inboard activated via levers.  Is that what you plan?  Maybe I just don't understand how it all works,

https://www.google.com/search?q=Alfa+Romeo+GTA+sliding+block+rear+end&tbm=isch&tbs=rimg:CYL96d6VCFiAIjiAGTyWJABapoF9TECTR88UH8nanp6wvxgtZ8pcJ9_1L1SRRkkARIMqeljvNP9wt_1C89vI2hn0kJcyoSCYAZPJYkAFqmET-DsWwjQJJwKhIJgX1MQJNHzxQRaohDzPg_19GgqEgkfydqenrC_1GBF8-TZyI9fWGioSCS1nylwn38vVETZNaY7cvRLpKhIJJFGSQBEgyp4R7Rvkq-CEHksqEgmWO80_13C38LxEQrMSmIfphqSoSCT28jaGfSQlzEafgkzbsLFk3&tbo=u&sa=X&ved=0ahUKEwi4usfNlsLYAhUHvVMKHa11AbIQ9C8IHw&biw=1163&bih=536&dpr=1.65#imgrc=gBk8liQAWqbDKM:

Sumner







Title: Re: Lakester Front Suspension
Post by: awelker on January 06, 2018, 04:26:55 PM
I used a slide block for axle locating on the front of my bellytank.  An aluminum bronze square block rides in the steel front shock support. I don't have a great picture handy but in the first picture you can see the hole in the center of the axle and the vertical slot behind it.  Worked well other than the fact that it was a bit noisy at low speeds, I think the fit could have been a bit tighter but I didn't want to get any binding.  It was simple and compact, and since this was a front suspension redesign it worked in the space I had available.

Andy

(https://farm2.staticflickr.com/1681/26435774082_04e6bb7a8c_z.jpg) (https://flic.kr/p/Gh3fCj)Untitled (https://flic.kr/p/Gh3fCj) by Andrew Welker (https://www.flickr.com/photos/vonwelker/), on Flickr

(https://farm2.staticflickr.com/1528/26528120205_d552ea6cff_z.jpg) (https://flic.kr/p/GqcxUR)Untitled (https://flic.kr/p/GqcxUR) by Andrew Welker (https://www.flickr.com/photos/vonwelker/), on Flickr


Title: Re: Lakester Front Suspension
Post by: Lemming Motors on January 08, 2018, 07:11:24 AM
Thanks Sumner for the snips and Andy for a real world example (sliding block).

I'll attach a sketch I did. My intention is that the springs / shocks will be lever operated though it has only just dawned on me that there must be a short intermediate link between the chassis and the shock lever arm (thinking the Seth Hammond front end) to account for the different arc lengths - I had thought this mechanism might contribute a little to axle control (fore and aft) but not if there is an extra pivot in the system.

I had a wind tunnel guy convince me to go for rounded underbelly to bleed air and not have any ground affect and therefore no 'aero transitions' - unfortunately that means the fuselage tapers towards the ground and so keeping everything inboard (trailing arms, or 4-bars, or hairpin as I've drawn it) is within a relatively narrow space (not the full 24" as Bockscar has it) and that worries me for wheel control with a 44-48" proposed front track.

John



Title: Re: Lakester Front Suspension
Post by: manta22 on January 08, 2018, 10:55:10 AM
John;

You could replace the pin slider with a large ball or roller bearing. This would give lower friction and eliminate the lubrication problems. All you need for sliding track clearance is a few thousandths.

Regards, Neil  Tucson, AZ


Title: Re: Lakester Front Suspension
Post by: Rex Schimmer on January 08, 2018, 03:29:17 PM
John,
Go back to my post on the first page of this thread and look at the way that we are locating the axle, skip all of the monkey motion that we went through to get the shocks inside the body. The axle is located by three arms, the lower ones, that also link the shocks to the axle and the middle one that is located approx 7 inches above the lowers and provides lateral location and also front to back location. It also provides the means to set the axle caster. Our axle is 44 inches between king pins and the front of our car is pretty lite, approx 400 lbs. All of this is located inside a tank that is around 13-15 inches in diameter at the axle area. We have ran this last year at the SCTA meet and even with the rough course we had no handling problems related to the front axle, that we know of at least. If you do go with a four bar or hair pin radius rods I would highly suggest using a three bar set up as it will prevent the inherent binding of a four bar or hair pin set up as they try to twist the axle in situations in which one wheel is raised above the other.

I agree with our aero guy to go with a round section design, much more work but much better aerodynamics. Flat bottom cars are so much more easy to build but not optimum for aero.

Rex


Title: Re: Lakester Front Suspension
Post by: Lemming Motors on January 09, 2018, 04:08:42 AM
Rex
Thank you :cheers:
I had not realised that your Lakester had run (when looking at the pics you included in the thread).
That gives me a lot of confidence to 'sign off' my front end thoughts and start designing some other detail.

I have pretty much finished my waste pipe and duct tape model - I am not sure Tech will sign off on the duct tape though.
It has proved invaluable. e.g. bail out (some changes in the knee area required - mentioned by someone already) and from the original drawings I have also made several changes to the cockpit length. My frontal area is a little large (I've read the threads - no comment needed) but by making a ply firewall and mating the engine to it I cant go much smaller without bulges so it is what it is.

John
 


Title: Re: Lakester Front Suspension
Post by: Sumner on January 09, 2018, 08:06:02 AM
John I like you cage structure. A couple thoughts from a distance, so take them with a grain of salt. 

I'd think about giving yourself a bit more room above the helmet.  Not sure if that helmet meets current specs.  If it doesn't you might find that one that does is a fair bit larger and at this point you don't have any padding on the bar above it either.  Both could soon crowd that area.  I used an older helmet and now will have to raise the cage a bit.

(http://1fatgmc.com/car/misc-pics-1/John%20Lakester-1.jpg)


In the picture above I'm suggesting taking that step out of the floor bottom.  Without it you can slide forward to get you head out easier and then slide your feet and legs back a bit to clear the bar with your knees.  Doing this wouldn't add anything to your frontal area.  Also on our cars the frontal area is the largest cross-section of the car, most likely at your back area or in the engine compartment.  If so making things a little larger up front aren't going to impact the frontal area.

The best on your lakester build,

Sumner


Title: Re: Lakester Front Suspension
Post by: Lemming Motors on January 09, 2018, 08:30:17 AM
Thanks for the comments Sumner. I have spent a lot of work time on your site and its links (hope my boss isn't on this forum).
The stepped seat is actually really comfortable and I have no trouble with exit but, and your point is well made, while that is a new (borrowed motorcycle) helmet it is not necessarily a current Snell one and so I still have to go buy one of those before that roll structure is signed off.

Sorry - my build pic has hijacked this front end thread.

To recover a bit - the step chassis under the legs is intended to accommodate the axle (not aero) meaning it is mounted at a relatively wide part of the chassis allowing adequate body work forward of it to taper to the nose. Moving the axle ahead of the feet would mean adding at least a foot or more to the length and I can't see any advantage - I guess there is no disadvantage for length (except transport from England) and maybe surface area but I doubt my eyeball aero is subtle enough for that to be a factor.

John


Title: Re: Lakester Front Suspension
Post by: Sumner on January 09, 2018, 09:20:59 AM
....To recover a bit - the step chassis under the legs is intended to accommodate the axle....John
That makes sense..didn't realize the axle was in that area.. :-P

Sumner


Title: Re: Lakester Front Suspension
Post by: SPARKY on January 09, 2018, 09:27:29 AM
love the duct tape---To Sum's point do not forget  fire suit thickness it moves one forward as well as up---that was the main reason we had to re do our front cage hoop. It was my second rodeo and we still screwed it up---also --are you using 7 or 9 point harness---it also changes things some.


Title: Re: Lakester Front Suspension
Post by: Lemming Motors on January 09, 2018, 09:59:07 AM
Thanks Sparky
Looks like I will have to get suited and booted before final measurements :oops:

I have Lakester front questions;

1. a number that have been proposed on this thread have the rack attached to the axle - no bump steer - yeah. I assume (?) therefore that the lower (rack end of) the steering column has a splined section to accommodate small changes in length required by the vertical movement of the axle altering the (relative) length of the column? If that is the case can anyone supply a manufacturer or photos of what is acceptable?

2. are spindle mounted non-ferrous front wheels accepted in the 200 and a little bit mph classes?


John


Title: Re: Lakester Front Suspension
Post by: awelker on January 09, 2018, 10:34:36 AM
I used a Woodward MC rack that is mounted to my axle. Rack just has a short spline but they also sell telescoping shafts. Somewhere I have a CAD drawing of my rack if interested.

http://www.woodwardsteering.com/catalog2017.html



Title: Re: Lakester Front Suspension
Post by: Lemming Motors on January 09, 2018, 11:04:11 AM
The Woodward catalogue shows splined yolks which answers my question and has a really good description of how u-joints deliver different shafts speeds at different times as they go through rotation and how double u-joints help that at higher angles and especially how to phase u-joints on a shaft - really interesting. Thanks.
John


Title: Re: Lakester Front Suspension
Post by: Stainless1 on January 09, 2018, 11:31:54 AM
Sliding d shafts can be salvaged from a variety of cars and found on ebay.  John, start a build diary....
Yes spindle mounted aluminum wheels are allowed, but magnesium wheels are not.
It looked like you have a single bar over your helmet, split that into 2 bars and you will gain head space.  Plate over them and you head will be better protected. 
If you can find a center load rack, it will allow longer tie rods... good luck with your build.


Title: Re: Lakester Front Suspension
Post by: SPARKY on January 09, 2018, 04:17:25 PM
To SS1 point  the flat plate added between the two bars--not to stick up above them--really makes it nice to put the flat SFI padding on above and behind the helmet should not lose clearance


Title: Re: Lakester Front Suspension
Post by: Skip Pipes on January 09, 2018, 08:45:07 PM
John,

Your frame/cage mock-up is superb. You should start a thread in Technical Discussions and re-post these pics so we can flush these design concepts. My chassis design is similar so I want to get Sumner's further guidance.

Skip Pipes


Title: Re: Lakester Front Suspension
Post by: NathanStewart on January 11, 2018, 03:29:47 PM
Both you and Nathan are pretty stout guys, are you considering a "slimmer" driver, cuts down on the frontal area.

Luckily for me, even though the engine is an inline 6, the turbo hanging off one side and intake manifold hanging off the other means I fit within those confines very easily. 


Title: Re: Lakester Front Suspension
Post by: NathanStewart on January 11, 2018, 03:33:06 PM
John, Your frame/cage mock-up is superb.

I concur.  I really like the raised floor for better driver ergonomics.  Very formula car-ish.  You don't always have to build things to be stupid simple.  A little design pizzazz goes a long way. 


Title: Re: Lakester Front Suspension
Post by: Lemming Motors on January 12, 2018, 04:12:58 AM
Thanks for the positive comments - I have started a build thread as suggested: UK Lakester Build G/GL.
John