Jump to content
ajh

Lowered spring seats.

Recommended Posts

Anyone have photos of examples of lowering spring top seats on the chassis and how they re-braced things? Working on a RRC LWB chassis that's getting a Series hybrid body for a strictly OHV toy and wondering if that's a reasonable approach.

 

Share this post


Link to post
Share on other sites

 

22 minutes ago, ajh said:

Anyone have photos of examples of lowering spring top seats on the chassis and how they re-braced things? Working on a RRC LWB chassis that's getting a Series hybrid body for a strictly OHV toy and wondering if that's a reasonable approach.

 

I'm not sure what OHV means in this context,. Off Highway Vehicle? If it is then I would try my hardest to talk you out of it and instead get you to raise them and use longer springs instead of lowering them. We normally use OHV as the acronym for Overhead Valve as applied to engines.

Springs have a minimum length that should see your spring seat at least as high as the bottom of the chassis plus the compressed length of your spring, you don't want the spring to become coil bound and for the spring seat to become the bump stop. Remember the axle comes up higher than the bottom of the chassis during articulation. I'd think carefully about lowering the spring seat and what it will achieve. It'll also raise the centre of gravity of the vehicle to no advantage whatsoever and will decrease useful wheel travel as the propshaft will limit droop and you're going to lose bump travel. You'll also lose articulation as the lowered bump height with the same droop at the chassis will compound the loss.

Maybe I'm completely off track of course and totally misunderstood. Maybe a wee bit more explanation for the hard of thinking amongst us.

If you are determined to lower them like for a road only lifted mall crawler you could maybe build some temporary spring spacers and see how you like it first before committing to cutting the chassis.
 

Share this post


Link to post
Share on other sites

If you are lowering the spring seats and need advice on the details of how to reinforce them, then I would suggest you do not have enough knowledge in suspension design to properly change everything else to make it a safe system.  An internet forum is not the place to gain this knowledge, IMO.  

Share this post


Link to post
Share on other sites

Jamie, yes Off Highway Vehicle, legal class of vehicle here for ones like UTVs etc.  I realize I'd need extended bump stops, probably cheaper active ones, but what's the real difference between lowering the chassis end and using axle seat end spacers then?  I was going to do tube wings etc so wondering how people tied things in, I've looked at ones like the Tomcat, and ideally I'd just go coil-over and forget the brackets entirely but this build is 'stuff lying around' more than something with a budget. :) The other points are well taken though.

Red, just because I'm curious what other people have done doesn't mean I can't make something work. 

Edited by ajh

Share this post


Link to post
Share on other sites

Making something work and understanding suspension design and how to design things to safely take the load are different items.  Moving the spring seats is a very simple and basic item.  The point being, if you need to ask about something that basic, you most likely do not have enough knowledge to do more important items safely and you should involve someone that does.

Lowering the spring seats without also changing all of the linkage mounts results is poor suspension geometry.

Share this post


Link to post
Share on other sites

when gigglepin built there D90XX along with Stefans 100", they had lowered spring seats to give them a subtle lift without requiring tall springs, worked well at the time & I know that D90XX is still competing now in ultra4 with the same suspension setup

  • Like 1

Share this post


Link to post
Share on other sites

With everything else in the suspension system changed and very well engineered by people that know what they are doing.

Edited by Red90

Share this post


Link to post
Share on other sites
7 hours ago, ajh said:

but what's the real difference between lowering the chassis end and using axle seat end spacers then?

I'd suggest both are as horrific as each other and have no place on a vehicle with a chance of venturing off highway. I suggested spacers just as an alternative to cutting the chassis and doing irreversible harm. 

If you're using stuff that's lying around and you are confident with your fabrication skills you could build something pretty tasty. A lot depends on your list of ingredients.

Alternatively, look at what you would need to do to turn your project into a low rider with big tyres then put longer softer springs and dampers and you'd be further on the track to having a decent off roader. What wheelbase is your project going to end up and how much rear overhang? Where's the fuel tank and battery going? 

Measure your front radius arms and draw them or mock them up on your workshop wall. Move it through a range of motion and using that explain how you would like it to move and we can probably point you in the direction of that. Getting the front end to work is the first thing and there are a number of tried and tested ways of doing it.but you need to first understand what's happening there to let us better help you. In many ways the back's easier to deal with. Have a wee look at antidive and have a clear picture of what actually happens with radius arms during articulation. What type of terrain will you be driving and do you have any locking differentials?

Why not just run the series landy as is and modify it instead of potentially ruining two vehicles?  Tube frame on the Range Rover?

 

Share this post


Link to post
Share on other sites
6 hours ago, RedLineMike said:

when gigglepin built there D90XX along with Stefans 100", they had lowered spring seats to give them a subtle lift without requiring tall springs, worked well at the time & I know that D90XX is still competing now in ultra4 with the same suspension setup

I wasn't going to post this but seeing as you mentioned it, here is exactly that chassis. Notice the A frame crossmember underneath the chassis and no trailing arm mounts as such. It's not really a Land Rover chassis as much as a very cleverly designed object to look like a land rover chassis. You could equally say they started with the suspension and built the vehicle round about it. It was amazingly light, no wonder they won everything. I've no idea how heavy it got with mud.

Copying the spring seats from this would be an option but I'd still say not to on a standard chassis and suspension.

IMG_7387.jpg

Share this post


Link to post
Share on other sites

that's not the D90XX chassis,

that's Ryan Jenkins cheese grater,  different car

Edited by RedLineMike

Share this post


Link to post
Share on other sites

It's worth looking to Iceland for inspiration if you're wanting to lower the mounts on the chassis, it's what they tend to do for their big tyre conversions.

Share this post


Link to post
Share on other sites

Thanks for the input; the main reason I was looking at it was because the donor I'm using has some bits I'd like to repair and to do so I'd have to cut the mounts anyway. Since it's a trail only rig I have more freedom than I would if it needed to be on-road as well, and I'm already working on a stock height D2 chassis based Tomcat, so this is more or less just spare parts coming together. There isn't a 'Series' to restore, just a Series bulkhead, no RRC to build on, just the good parts of the LWB chassis, etc. :)

Share this post


Link to post
Share on other sites

Also, thanks for that photo, I've often wondered why more people don't die flare the chassis to save weight. That is my end goal once the Tomcat is done, build a second from scratch including the chassis and lighten it as much as possible in the process. Ideally all alloy, but that's probably far-fetched at this point due to resources. Over here there isn't a very big community of people doing builds of anything much beyond rebuilds so there is seldom much to go look at for ideas, and when there is it is generally a 20h drive away, so having various things pointed out that I haven't come across is really helpful just for expanding ideas.

 

Share this post


Link to post
Share on other sites
On 11/20/2018 at 3:04 AM, Red90 said:

If you are lowering the spring seats and need advice on the details of how to reinforce them, then I would suggest you do not have enough knowledge in suspension design to properly change everything else to make it a safe system.  An internet forum is not the place to gain this knowledge, IMO.  

Without sounding silly about it, it is as good a place as any other to learn.... it is where I started learning, and still learn, Long travel beam axle suspension has been by passed by main stream suspension makers and major sports groups so there are no modern books on the subject, (most of my books are based on stuff from the single seat home built sports car of the 50-60's) there isn't even a universally recognized pattern for people to follow........ over the 15+ yrs I've been playing with beam axle suspension I've watched and participated in changing scores (AS/AD, roll center heights, instant center heights etc)...... Lol and my latest build challenges past and current thinking on the subject 

Forums are the only place you can easily get up to date information on the subject...... 

Given the reference to tomcats I'm assuming this is to have some performance .... then in my opinion this is a better option than HD lifted springs, move the seats on the chassis down and stay with the original soft spring..... depending on how hard you plan on hitting things and how big you want to go lol

As for the engineering side of things notice how the spring seat has sides that go down the sides to tie to the bottom of the chassis.... I would wrap them around the bottom and on the top weld some plate to the top of the seat and carry it to the top of the chassis..... you want to transfer your load from the spring to both top and bottom of the chassis so there is no point load on the chassis wall that can tear out or punch in due to the twisting load applied to the spring seat 

Forget about alloy for a chassis lol there is a very good reason why you don't see it in offroad chassis's it is due to the fatigue issue of alloy.... basically every little bump no matter how small is counted towards the lifespan of the material before it cracks, steel on the other hand has a threshold bumps under this don't count this makes steel last 

As for dimple die'd chassis rails lol you know how much work is in that! and the gain isn't really lol Now there are areas you won't do this too, areas like around the spring seats, suspension mounts, engine mounts etc so at best you are taking a couple of kg out of it (a better weight saving would be to not galv it lol) so at the start of the race your 2 kg lighter but every time you hit the mud this drops and after a while you have that much mud in there you are carrying more than you saved. I used to be involved in speedway (dirt flat track) the top guys used to spray baby oil on the undersides of there cars to stop the clay sticking to help them win.... if your going to go to the trouble of fabricating a whole chassis space frame it a way better gain than an old ladder chassis 

 

Share this post


Link to post
Share on other sites
On ‎11‎/‎21‎/‎2018 at 2:01 PM, ajh said:

Also, thanks for that photo, I've often wondered why more people don't die flare the chassis to save weight. That is my end goal once the Tomcat is done, build a second from scratch including the chassis and lighten it as much as possible in the process. Ideally all alloy, but that's probably far-fetched at this point due to resources. Over here there isn't a very big community of people doing builds of anything much beyond rebuilds so there is seldom much to go look at for ideas, and when there is it is generally a 20h drive away, so having various things pointed out that I haven't come across is really helpful just for expanding ideas.

 

im aware that those "cheese Grater" chassis have a reputation for cracking, given the work involved to build them im on the fence if they are worth it

 

Share this post


Link to post
Share on other sites
On 11/25/2018 at 3:36 PM, RedLineMike said:

im aware that those "cheese Grater" chassis have a reputation for cracking, given the work involved to build them im on the fence if they are worth it

 

Indeed, when poorly placed or incorrectly flared they're not great. My plan was to actually do just the sides then probably put something over the holes and leave the top and bottom intact, but that also assumes the chassis is a basic one. Once you have an integrated safety cell/cage as well the rigidity goes way, way, up and the flex dynamics change entirely. Still, need to finish the first D2 Tomcat before I can look at making one lighter. :)

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy