russbost
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| posted on 4/2/19 at 02:23 PM |
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Shortening steering arms
I've had a customer ask me if it's feasible to shorten the steering arms to speed up the steering response - bit like fitting a
"fast rack" which isn't an option in this case
Obviously it's going to affect Ackerman slightly, tho' I doubt that would cause problems. Just trying to get my head around what else it
might affect & wondered if anyone had actually done it & with what results?
Is there any simple way of working out how much length change will produce what ratio of lock to lock change (we'd need to use different length
rack spacers to keep lock at same turning circle as current) or is it a case of having to do the basic geometry calcs
Any info & educated comment welcome!
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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steve m
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| posted on 4/2/19 at 02:35 PM |
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It will mean heavier input will need to be applied, as it will have less leverage
a quick rack would be the way to go, and not play with an already perfect ratio on the uprights
Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at
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nick205
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| posted on 4/2/19 at 02:37 PM |
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If you're asking about shortening the track rods then how would this speed up the steering?
It wouldn't alter the gear ratio between the rack and pinion of the rack so I can't see how it changes the speed of steering. If
I'm misunderstanding the question please correct me.
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russbost
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| posted on 4/2/19 at 02:49 PM |
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nick205, no, not the track rods, the steering arms, (the section that joins the track rod end to the actual hub) they are our own in laser cut mild
steel, so no problem in cutting/welding.
Re heavier input surely that would be the same with a quick rack as in both cases you are changing the ratio between input & output?
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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nick205
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| posted on 4/2/19 at 03:44 PM |
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quote:
Originally posted by russbost
nick205, no, not the track rods, the steering arms, (the section that joins the track rod end to the actual hub) they are our own in laser cut mild
steel, so no problem in cutting/welding.
Re heavier input surely that would be the same with a quick rack as in both cases you are changing the ratio between input & output?
Thanks - now I understand what you're referring to and the thought process.
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rusty nuts
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| posted on 4/2/19 at 05:01 PM |
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Might be better to make or use shorter arms from a different vehicle? Shortening the present arms is likely to involve welding which was and probably
still is,an MOT failure unless it is part of the manufacturing process ,if the vehicle in question is a road vehicle Would it be possible to use a
smaller steering wheel?
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russbost
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| posted on 4/2/19 at 05:38 PM |
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As we manufacture the arms in the first place, I can't see how it could ever be an MoT fail, as we would simply have "manufactured"
shorter arms - having now thought a little more on this I realise I can maintain Ackerman by locating the track rod end tapers on the same
"Ackerman line" back to the centre of rear axle as we used originally.
So far as I can see/think without having any easy way of modelling it it shouldn't affect bump steer & all other caster/camber/KPI angles
will be maintained - just trying to make sure I'm not missing something glaringly obvious. It will change the angle in the longitudinal plane of
the steering rack by a degree or two, but I'm not seeing anything that would make that a problem
Going for a smaller steering wheel would make the steering feel heavier & would increase the gearing in terms of angular input, but wouldn't
affect the no. of turns in going from full lock to full lock, which is what the customer's aim is
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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Dingz
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| posted on 5/2/19 at 08:43 AM |
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I guess the ratio change wii be the same as the reduction in the arm length from the ball joit centre to the king pin? Centre. Ie reduce the arm10% =
10% more effort required and 10% more movement.
Phoned the local ramblers club today, but the bloke who answered just
went on and on.
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Bluemoon
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| posted on 5/2/19 at 08:43 AM |
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Some uprights have removable arms is this something you can do? Would allow adjustments latter to satisfy customer?
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JAG
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| posted on 5/2/19 at 08:45 AM |
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Yeah - higher steering wheel torques required
Also; potential for steering judder increases as you shorten the input arm on the Knuckles. Wheel input loads have a greater output when measured at
the Track Rod End location on the Knuckle and can overcome the Driver under some circumstances - leading to Steering Wheel vibrations also known as
Steering Judder.
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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Camber Dave
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| posted on 5/2/19 at 08:54 AM |
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The 'included angle' between the steering arm and track rod does affect the ackerman angle.
Rule of thumb
Front rack - Move forward reduces Ackerman (increase included angle)
Move closer to axle C/L increases Ackerman (reduced included angle)
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russbost
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| posted on 5/2/19 at 02:20 PM |
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Camber Dave, are you sure about that, surely if you move the track rod end location point along the ackermann line between pivot point, TRE &
centre of axle the ackermann will remain the same. I guess there could be a fractional change due to the changed angle of the track rod, but that
would be very minor, or am I missing something?
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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Camber Dave
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| posted on 5/2/19 at 03:35 PM |
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Hi Russ
I first encountered it on a car I was setting up. It had measurable ackerman but steering arms were cranked to align with the kingpin width.
I did a drawing in plan to understand where it came from.
Conventionally the rack is placed to give straight track rods. This typically gives steering angles of 20 & 23/24 deg.
In your case shortening the steering arms will mean the arm/track rod angle will slightly more than 90 deg
When the rack moves the angular displacement of the uprights will be different than before.
When I got a later edition of Allan Staniforth's 'Bible' it was all explained in a revised Chapter 4.
He had the same experience, and modified his Megapin with success.
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Angel Acevedo
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| posted on 5/2/19 at 03:50 PM |
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Yes it can be done.
Things to consider.
New hole center is in line with the line that joins the old hole center to the King Pin Axis.
Shorter arm means more effort.
Lock to Lock will be less turns for the same amount of turning radius.
Or same lock to lock turns will yield shorter turning radius.
Ackerman may remain the same provided you shift steering rack back the same amount that the holes have been moved back (Front Steer) or forward (Rear
Steer)
Change in ackerman may be so minute that may not be worth it to go through the hassle.
All this is based upon my understanding of books I´ve read but have no Hands On experience, I hpe this may help you make up your mind.
AA
Beware of what you wish.. for it may come true....
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russbost
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| posted on 5/2/19 at 06:26 PM |
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Many thanks guys, that's clarified a no. of issues that were giving me some concern, I can now explain to the customer & at the end of the
day, it's his choice, he will have to accept that we are going into uncharted territory at his own risk!
I will do some basic drawings to see what looks sensible in terms of amount to move
Will try & remember to report back with results!
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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SPYDER
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| posted on 5/2/19 at 08:35 PM |
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If you maintain Ackerman you will be moving the hole outwards a small amount ie. toward the back of the disc.
Keep an eye on the clearance betwixt disc and TRE.
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owelly
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| posted on 6/2/19 at 12:18 PM |
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I was swapping steering arms on my buggy to try to sort the geo out....12mm difference in length had a huge impact on the ackerman. Any slight turn of
the steering had the hubs all over the place!!
http://www.ppcmag.co.uk
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russbost
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| posted on 6/2/19 at 01:10 PM |
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Owelly - that would suggest the new arms were not only shorter or longer, but had the TRE taper in a different place laterally, thus making major
changes to the Ackermann
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
|
NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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CNHSS1
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| posted on 7/2/19 at 05:58 PM |
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Shortening of arms is a common thing in the drift scene (moving ball joint closer to axle line) and you may need to add or move, the steering limit
stops to stop the inside tyre going over centre and jamming on lock or touching brake lines etc.
Some uprights (chevette and manta) have a bump in the upright casting as well as a stop in the rack, but not all cars do, so beware when mixing
components (like we do!)
As has been said small changes can have big consequences so slowly slowly catchy monkey... 
Good look.and like to see the pro
Ject as it progresses 
"Racing is life, everything else, before or after, is just waiting"---Steve McQueen
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Andy S
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| posted on 8/2/19 at 02:20 PM |
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quote:
Originally posted by russbost
Owelly - that would suggest the new arms were not only shorter or longer, but had the TRE taper in a different place laterally, thus making major
changes to the Ackermann
It's the angle of the steering arms in plan view that is the issue - as mentioned above - it is like moving the rack forward and changing the
angle of the track rods in relation to the rack C/L and the steering arm pivot. It is not in the static centre condition that there is any change or
possibly for that matter in bump and droop but in the actual steering of the car. There can be significant changes in the angular positions between
the inner and outer pivots on the rack that effect the resultant angles of each wheel in relation to one another that does not follow the form of
Ackerman in maintaining the inner and outer wheel angles in the relationship required.
Moving the pivot location on the steering arms and then moving the rack back so that the existing alignment is retained would maintain that balance
but there may also be requirement to raise or lower the rack as well to ensure correct alignment in bump and droop due to the outer pivot location
moving either in or outboard in relation to the original inner rack pivot location.
Which is why a faster rack is typically the preferred option
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Mr Whippy
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| posted on 8/2/19 at 06:01 PM |
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This thread is quite funny
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russbost
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| posted on 8/2/19 at 06:04 PM |
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Mr Whippy, I think you need to get out more!
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
|
NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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russbost
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| posted on 30/4/19 at 12:39 PM |
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Just thought I would give an update on this.
Ok, so I moved the TRE taper location back down the Ackermann line by around 12mm (I say "around" because I was locating the TRE position
by a location already part of the laser cut steering arms as that seemed a lot more accurate than attempting to measure from a hole centre to a new
"floating" position). This increased the angle on the track rods (there is already a slight angle from the rack mounting to standard TRE
position) by a couple of degrees.
The result - it increased the gearing on the rack from 3 & 1/8 turns lock to lock to 2 & 1/2 turns - exactly the result wanted by the
customer. No noticeable difference in general road handling & performance. I did feel that it may possibly have made the car somewhat more
susceptible to feedback thro' the steering on very bumpy roads, tho' obviously that's a highly subjective thing with no way easily
of objectively measuring it. Steering didn't feel noticeably heavier (front of the car is very light anyway).
Hope this has been helpful & informative!
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
|
NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
|
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