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Author Topic: UK Lakester build G/GL  (Read 101722 times)

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Offline kiwi belly tank

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Re: UK Lakester build G/GL
« Reply #135 on: October 29, 2018, 10:30:58 AM »
Overkill's not a problem, especially in the front. You'll likely need a location to add ballast in the future.
  Sid.

Offline Lemming Motors

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Re: UK Lakester build G/GL
« Reply #136 on: October 29, 2018, 10:34:13 AM »
Hey Sid
Ballast is easy - eat more pies, drink more ale.  :cheers:
A Bonneville Lakester please barman.
Certainly sir; a lick of salt, a sip of gas and a twist of Lemming. More Lemming sir?
Just a squeeze.

A Squeeze of Lemming it is sir.

Offline tauruck

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Re: UK Lakester build G/GL
« Reply #137 on: October 29, 2018, 11:57:01 AM »
You can't deny that you're loving this and you're being consumed!!!!!!.
Sodium addiction. :-D :-D :-D :-D

Offline Rex Schimmer

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Re: UK Lakester build G/GL
« Reply #138 on: October 29, 2018, 09:09:22 PM »
As my materials instructor , HP Davis, always said "When in doubt, make it stout"! Looking good.

Rex
Rex

Not much matters and the rest doesn't matter at all.

Offline Lemming Motors

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Re: UK Lakester build G/GL
« Reply #139 on: November 05, 2018, 07:55:02 AM »
A steering question.

On the Seth Hammond lakester the steering rack (appears) to be attached to the tube axle and by crude isometric calculation has a track at the front around 48". The rack appears to be about 12" wide from rose joint to rose joint. In that configuration the rack will go up and down with the axle and there will be zero bump steer. In the case where the steering column is long and at a shallow angle it will travel through a very shallow arc. which appears to be case in the Hammond configuration.

I am mounting my axle relatively close to the steering wheel (i.e. under my legs) and so the column would go through a very steep angle. Too steep for practical purposes with the rack travelling with the axle.  One option is to take it through a 90 degree steering bevel box and have the rack's pinion mounted vertically with a sliding spline between it and the bevel box.

Opinions please - is there a risk to the steering relying on a vertical sliding spline not to bind and would I be better rigidly mounting the rack to the chassis, having no movement in the column and sucking up the bump steer (if any)? I am assuming no more than 1 to 1.5" of wheel travel in bump. A wide track would give less bump steer?
A Bonneville Lakester please barman.
Certainly sir; a lick of salt, a sip of gas and a twist of Lemming. More Lemming sir?
Just a squeeze.

A Squeeze of Lemming it is sir.

Offline Stainless1

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Re: UK Lakester build G/GL
« Reply #140 on: November 05, 2018, 10:25:21 AM »
We eliminated our bump steer with a rack mounted to the axle.  We use a center load rack which allows longer tie rods.  Nothing says your rack has to be mounted vertical or horizontal... find the optimal angle.  Do not use a sliding spline, it will bind... use a D or double D... those are used on collapsible steering columns in a lot of cars, available parts and aftermarket pieces are found on Ebay.  Use as many u-joints as required.
Or don't use a rack if you can't find the angle... You can still mount an arm type steering box with a long shaft on the axle.... keep tie-rods as level as possible.  Either way, you need a slider on the steering column. 
We also use a steering quickener... 2:1 but mounted in reverse so it is a steering slower.  Round-e-round cars use them to turn faster, they work both ways.
Stainless
Red Hat 228.039, 2001, 65ci, MSA Bockscar Lakester with a little N20 
MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.

Offline kiwi belly tank

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Re: UK Lakester build G/GL
« Reply #141 on: November 06, 2018, 12:42:55 PM »
Mounting a rack to the chassis with a live axle is a horrible decision, as is having a sliding coupler on an axle mounted rack with a vertical pinion. A rack n pinion is also too fast & will need to be slowed down to lessen the sensitivity. mounting to the axle also adds un-sprung weight to the front end.
Drag link steering works fine on a lakester if it's all on the same plain, even with a center mounted steering box. My tank is this way, street legal with softer suspension, 5" of travel & see's the occasional 200+mph pass on US Hwy 30 & drives like a pi$$ed off Cadillac.
What are the deciding factors on having the front end so far back in the chassis that you're sitting on it?
  Sid. 

Offline Lemming Motors

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Re: UK Lakester build G/GL
« Reply #142 on: November 07, 2018, 05:19:52 AM »
Thanks Sid, Stainless

Confession time; during the chassis mock-up phase I moved the 'dash' hoop forward a couple of times to facilitate getting in and out (knee clearance).
I  fixed the position of the pedals (now adjustable for shorter legs which complicates things slightly) but I completely failed to push the axle point forward by the same amount as the dash hoop, or, put another way, the required steering column angle got steeper. Why cant I move it forward? There is a lovely cross brace under the floor and in the original drawings the axle was under that with the 'rack' a few inches behind meaning that the column could go through the floor just behind the intersection of those tubes - it made sense at the time.  :roll: I can move the axle forward a few inches from the planned location and using double UJs can probably do a nice steering column to a chassis mounted steering box (source please).

The design concept of having the axle under your ankles / calves was to allow 4 bars etc. to be inside the body work (i.e. under the leggies) and put some weight on the front springs reducing the need for ballast weight for weight distribution. That of course assumes that locating the rad, fuel etc. rearward of the engine will put enough on the rear wheels for traction. 65 - 70% I assume is the target - off topic - coincidentally that's what my '69 Lotus Europa had with a Ford Focus 2 litre on ITBs etc and that left the line like salt off a shovel and handled far better than most moderns.
Vertical pushrods from the front axle are planned to operate rockers in the cockpit activating horizontally mounted coil overs above the legs.

The original plan was to use a 20:1 small rack, mounted on the axle. Since the steering column will now be quite steep it seemed logical to explore a 90 degree steering bevel box (Toyota Hiace, cab over axle HKD model). That creates a need for a vertically sliding column to accommodate bump and rebound. A nylon bushed sliding spline column was sourced but that has received warnings (thank you). I am not sure why double D would be better though?

I was looking at the 20:1 Stiletto rack on axle because I had
1. studied the Seth H Lakester pics and liked it, and
2. assumed that for a steering box in the centre of the vehicle any drag link from a chassis mounted box (i.e. a hot rod style front end) would, at only ~half the track width, be too short, and create bump steer. 

I guess if there is only 1.5" of front wheel travel in bump then a 20" - 25" drag link (with a full width tie rod) might work. I am not sure what steering box is slow enough. My parts sources are limited in the UK - any recommendation for a suitable steering box and Sid, how long are the steering arms and pitman arm on your Lakester - do you have pics of the steering box etc. by any chance?

Lemming John
A Bonneville Lakester please barman.
Certainly sir; a lick of salt, a sip of gas and a twist of Lemming. More Lemming sir?
Just a squeeze.

A Squeeze of Lemming it is sir.

Offline kiwi belly tank

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Re: UK Lakester build G/GL
« Reply #143 on: November 08, 2018, 12:17:11 AM »
My first stop for that kind of stuff is the junkyard. In the tank I used non power box out of a mid 80's Mazda pickup, it worked best for that situation but look at all that old Jap junk. The box I ended up using in the liner is an FJ-60 Landcruiser & it's up side down to get the steering shaft under the diff & above the front tunnel.
I build a new steering arm, cut out a keyhole shape in the end & press in a section of the old splined end & weld it in. Then you can set the length you like to set ratio you like.
Front axle in the tank is a ball joint tube axle from a Jeep & the steering arms are stock length but I tweaked them to correct the Ackerman. Getting the ratio I like is all done at the steering box end. On the salt I like about 12 to 16 degrees total for one turn, anything much faster than that gets a bit too sensitive & can cause over input & on a short car that can mean pointing the wrong way on the salt.
Sitting basically on top of the axle you're not going to have much feel for what the chassis is doing since there won't be any good reference point ahead of you & if you build for 65 to 70% weight on the rear with a bunch of it behind the axle for the salt you will have a car with ducks disease that you probably won't like or worse! The heavy end likes to lead.
  Sid.

Offline Lemming Motors

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Re: UK Lakester build G/GL
« Reply #144 on: November 08, 2018, 06:34:57 AM »
Thanks Sid, I really appreciate the QC.

There will be body work forward of the driver. I race 2 person canoe and in the front seat it is harder to call the steering strokes than in the rear seat as the rear has more craft to align to the direction of travel so I do understand your point - I hope I haven't over done it and I obviously hope it will be driveable - time will tell. I agree with the weight point but surely you need rear axle weight for traction and a rear engine car will have a rear bias no matter what, hence the tail fins and etc. on most but then that creates a steering effect in a cross wind - eek. If the canoe is not trimmed properly (front to back weight) it definitely behaves as is if the pivot point is near the front so the arse swings in a cross wind - something aligned to CoP I assume vs. centre of hydrodynamic balance if that is even a thing.

Philosophically a front engine front wheel drive Lakester or Liner would make sense wrt weight and traction being I the same / right place.

UK breakers wont let you wander around anymore - you go up to a shiny office, order the part and they pick it (elf and safety guv'nor). Its more like a dealers parts department now. I miss NZ style wreckers where you take your box of tools and go rootling around and find something that you had in your head but don't know what make or model it comes from until you find it.

I am targeting something around 140" wheelbase with a 240" body (a bit less if its to fit in a 20' shipping container in one piece.)
I don't think my driving position will be much different to a trad. belly tank in terms of line of sight and there will be a lot of body work behind me trying to keep it straight (well, that's the hope).

I did find a 2:1 steering quickener online per Stainless' comment - never heard of them before then literally tripped over one on a site the next day. Serendipity. Shame it has a different spline and diameter to every rack and box on their site - surely that should be an industry standard, its nuts.

Interesting comment about Ackerman - I note that Stiletto (and probably Strange) spindles have none. I assume that dragsters and Lakesters go in straight lines and so wheel slip at manoeuvring speeds is not worth accounting for - I assume you have accounted for it for the road use, not the salt?
A Bonneville Lakester please barman.
Certainly sir; a lick of salt, a sip of gas and a twist of Lemming. More Lemming sir?
Just a squeeze.

A Squeeze of Lemming it is sir.

Offline manta22

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Re: UK Lakester build G/GL
« Reply #145 on: November 08, 2018, 09:49:31 AM »
Lemming;

Ackerman is useful on a race car for pushing the car around in the pits. In a straight line it does nothing at all but in a tight turn it keeps the tires from scrubbing.


Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline Lemming Motors

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Re: UK Lakester build G/GL
« Reply #146 on: November 08, 2018, 10:09:51 AM »
Thanks Neil

It wont need to be in the pits - start line, finish line, start line and repeat  :-D

Seriously though - noted.

Lemming John
A Bonneville Lakester please barman.
Certainly sir; a lick of salt, a sip of gas and a twist of Lemming. More Lemming sir?
Just a squeeze.

A Squeeze of Lemming it is sir.

Offline Stainless1

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Re: UK Lakester build G/GL
« Reply #147 on: November 08, 2018, 10:41:31 AM »
Our lakester was 51 rear and the lower gears could overpower the tires.... generally had slip equal to tire growth but have calculated 4-5% at times based on Trap speed and rpm with our small rear tires... but generally less than 1% with our Landspeed Goodyears.   The back of the drivers head was about at the CoG.
We had and will again have a 140 inch WB and an almost 20 ft car.
I would rethink layout to have the axle in front of your feet.
Any amount of bump steer on the salt these days is too much at 220 MPH.  Yes if you chassis mount your bell crank steering at the same height as your axle you will limit bump with long arms.... but mounting a rack on the axle far outweighs the problems created by unsprung weight.... Just my personal opinion....
I would not put a vertical slider in steering... another opinion, but like I said, you can find an angle to mount it.
I don't know what sliding splines you were planning, but the salt is not very forgiving and finds its way into everything.  We have used D shafts for about 30 years, as collapsible long shaft and as a slider for our steering rack mounted on the axle.  
As far as having all the same spline count on everything... it gets hard to do... and not really necessary.  Steering U joints can be purchased with their splines and shafts.... you are custom making everything anyway so matching all of that does not matter.  While having quick steering helps prevent the 20 point turn around, the slowest and smallest amount of steering is what you want at 200 MPH and up... I can guarantee you will never steer out of a spin with a special construction landspeed car... aero, CoG, CoP and your parachute will be the deciding factors in what happens.
 :cheers:
Stainless
Red Hat 228.039, 2001, 65ci, MSA Bockscar Lakester with a little N20 
MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.

Offline manta22

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Re: UK Lakester build G/GL
« Reply #148 on: November 08, 2018, 03:54:23 PM »
Stainless;

Your figure of 4-5% tire growth is similar to what my friend John Horsman told me- he allowed 4% for Le Mans & Spa, both high speed tracks. Those were not LSR tires, of course, but their Porsche 917s were running speeds of 240 mph.


Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline kiwi belly tank

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Re: UK Lakester build G/GL
« Reply #149 on: November 08, 2018, 05:06:20 PM »
You assume wrong John! I'm of the opinion that ALL front end geometry is more important on the salt due to there being a lot less traction for you to get response from.
Most people here on the forum know that Neil & I have a totally different opinion on the importance of Ackerman but it certainly doesn't mysteriously arrive at 45 degrees of wheel angle in the pits. It's progressive from 0 degrees & definitely as important as scrub radius, camber, caster & toe, especially if you start chasing it around on the salt.
Talk to lakester guys to get a better idea of what is undesirable.
Comparing canoes, Lotus Europa's & lakesters is like comparing apples & hand grenades & cheese graters.
Yes you need weight on the rear drive tires for traction but not to the detriment of balance. Understand the relevance of CP & CG, especially how they are more important on the salt than blacktop.
If you need to fit in a 20ft container, make the nose or tail or both removable. My liner is 40ft long but the last 10ft comes off for transport.
I'd hate to see you build a lemon & drag it over here only to be disappointed or get hurt.
  Sid.