LocostUSA.com

Learning how to build Lotus Seven replicas...together!
It is currently May 30, 2020, 7:31 am

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 47 posts ]  Go to page Previous  1, 2, 3, 4  Next
Author Message
PostPosted: May 27, 2015, 8:16 pm 
Offline
The voice of reason
User avatar

Joined: January 10, 2008, 4:47 pm
Posts: 7653
Location: Massachusetts
Well maybe I was grumpy this morning and didn't realize it. I'll try to explain my thoughts on this. Mind you I'm not certain about these things but it would seem worth it to try and measure things like this I think. I should be able to do some of that with my frame one of these days, so I'll try to get around to that and see how easy it is to do in the real world. My hope is that using a dial gage you could measure deflections with pretty small forces and not have to seriously anchor the frame to the floor.

Anyway, using Wright's picture above with the highlighting - I think the area highlighted in green/yellow is fine. That area is well triangulated and would basically function as a steel beam with a height of something like 12 inches. It's complicated a bit because there are bends in the rails, but basically it's a beam with two flanges and a web formed by those diagonals. This changes at the main roll bar hoop.

I can't see how the sub frame is attached, so I was sort of discounting that as a part of the structure. It's possible to bolt things together strongly, but I think there are a lot of ways to fall short too.

If the connection allows for play or a loss of strength - then you are depending on the strength of the upper rail tube right behind the roll bar. It will have all the weight of the car in bending. The rear roll bar supports go to the top of the bar and the forward ones go the the middle of the sides, so this is also being asked to bend, along with the upper rail.

These issues would go away if the rear braces for the roll bar joined at the height of the forward braces. Then you would have a beam from the front suspension to the rear suspension that was always more than 12" tall, just with a bit of a jog behind the roll bar.

I think this car would also benefit from something that would make an inner hoop for the dash.

All that said, maybe it is strong enough...

_________________
Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


Top
 Profile  
Reply with quote  
PostPosted: May 28, 2015, 1:54 am 
Offline
User avatar

Joined: April 26, 2008, 6:06 pm
Posts: 3058
Location: Under the weather. (Seattle)
As often happens when people post pics of of their incomplete build progress on this site, it's all too easy to comment based on the assumption that what you're seeing is already the finalized product. I would recommend reading up on the car here, as also linked in the previous thread about this car, before jumping to too many conclusions. While I certainly would not have followed the same path as them for a lot of the design decisions, the floating rear strut mount on the prototype chassis is actually a rather interesting idea for development purposes. Once that portion of the frame is welded from chassis tubing, any shortcomings with the rear chassis and rollbar strength could be easily addressed. It sounds like they already have a considerable number of improvements planned for their future cars:

Image

_________________
-Justin

Also follow my build on blogspot, tumblr, or instagram and twitter (GarageOdyssey)


Top
 Profile  
Reply with quote  
PostPosted: July 10, 2015, 10:18 am 
Offline

Joined: February 9, 2015, 6:31 pm
Posts: 19
Hey everybody,

Sorry for being late to the party. I'm Adam Doyle and my dad and I are the ones behind the DF Goblin.

Merim123 pointed out in his first post that we had planned to ship kits June 1. As with any project, we hit unforeseen delays and altered the schedule. We are currently still working on tooling up to make the kits.

The design has changed dramatically even compared to the rendering that Driven5 offered. I'd like to explain some of the changes and share some recent photos to show you how the car is turning out.

The car that we are building now, Prototype 2, is a Track Goblin. This means that it has a roll cage and mounts for aftermarket seats and race harnesses. Not all Goblins will have the upper halo and front down tubes, but other than that, the frame is the same.

The biggest change we've made was moving the fuel cell to a safer, more central location behind the seats. This dramatically decreases the chance of the tank being punctured in the event of a crash and allowed us to expand the capacity from just over 8 gallons to 11 gallons. This new spot has also allowed us to reuse the donor car's filler neck and cap. Here's a photo that shows the new tank mocked up in the new location (we are still bouncing between mounting techniques):

Image

In the photo you can also see that we decided to add a door bar around shoulder height. This bar will be in each Goblin regardless of it being a Track or City chassis. Adding this tube improves intrusion protection and will definitely make the chassis stiffer. The only downside is that the car will be slightly hard to get into, but we shot for a height similar to other exocars.

I'm sure some of you can guess at the next major thing we changed. With the fuel cell where the radiator used to be, we opted to put a 3 core aluminum radiator up at the front of the car where a radiator should be. This makes the car slightly more involved for the customer to assemble, but it will allow the car to run cooler, especially when the engine starts getting upgraded. The hood of the car will be a two piece design similar to a Lotus 7. The rear section will be the same as our current nose but approximately in line with the middle of the control arms we will cut it and continue forward with a second nose piece that has a large air opening.

We've also started fabricating the new front suspension. It has better geometry than the first prototype including shorter upper control arms for improved camber curves and the shock is mounted further outboard and is stood up more to increase it's effectiveness.

With the fuel cell removed from the front, we had enough room to fit the donor brake booster. We aren't sure if it will make the brakes too touchy, but it is easy to remove if so. We've also reused the donor electric power steering on this prototype. It too can be removed if it doesn't feel right for the car.

Here's a shot of the front:

Image

The lower radiator mount is incomplete in the photo. It will be fully fleshed out soon. You can see that the lower frame rail is open. We are going to run rubber hose through the lower frame rails to transfer the coolant between the front and rear. The rubber hose is a nice fit inside of the tube so we aren't concerned about chafing.

Here is a side view from several weeks ago that shows how the frame looks with a seat in it:
Image

You can see the aluminum fixture up front that bolts to the frame jig to align the front control arm and shock mounting points. There are also aluminum arms that extend back from this fixture to located the dash bar and accessories.

I hope I answered all of the questions in the thread. If not, or if you have more questions, let me know.


Top
 Profile  
Reply with quote  
PostPosted: July 10, 2015, 10:35 am 
Offline
Toyotaphobe
User avatar

Joined: April 5, 2008, 2:25 am
Posts: 4837
Location: Fort Worth, Texas
But have you actually driven it hard on a track or autocross course?

You were reluctant to do that initially. So I'm wondering how you know the suspension is set up right.

_________________
mobilito ergo sum
I drive therefore I am

I can explain it to you,
but I can't understand it for you.


Top
 Profile  
Reply with quote  
PostPosted: July 10, 2015, 10:45 am 
Offline

Joined: February 9, 2015, 6:31 pm
Posts: 19
It's pretty obvious looking back on the first prototype that the geometry was not good. We feel that racing it around an autocross wouldn't show us much about it. What the front suspension needed was a complete redesign starting with the mounting points of the control arms.

That is where the second prototype comes in. This one will allow for some worthwhile testing and will give us something to improve upon. It will see an autocross as soon as possible (even before body panels).


Top
 Profile  
Reply with quote  
PostPosted: July 10, 2015, 11:10 am 
Offline
User avatar

Joined: April 26, 2008, 6:06 pm
Posts: 3058
Location: Under the weather. (Seattle)
I think you're definitely going in the right direction with P2. :cheers:

_________________
-Justin

Also follow my build on blogspot, tumblr, or instagram and twitter (GarageOdyssey)


Top
 Profile  
Reply with quote  
PostPosted: July 10, 2015, 7:51 pm 
Offline
User avatar

Joined: December 7, 2012, 8:28 am
Posts: 1411
Location: Sarasota
P2 is looking much better.

For a track car though I still think you should go with rear double 'A' arm like the front. It makes adjustments so much easier. If you wanted to you could keep the lower control arm and just make the uppers. It would probably make your design simpler and better looking too.

Also go with adjustable coil overs at least an an option. Gaz shocks are under $1000 a set and very customizable to get what you want. Then with all that weight on the rear you should have an amazingly capable track car.

_________________
2015 & 2016 EMod Florida State Autocross Champion
2013 & 2014 DSP Florida State Autocross Champion

Scrap Metal Build Log viewtopic.php?f=35&t=14558


Top
 Profile  
Reply with quote  
PostPosted: July 12, 2015, 12:22 am 
Offline
User avatar

Joined: June 8, 2010, 8:02 pm
Posts: 619
Location: White Rock, BC, Canada
Hey Adam,

Firstly, good job! I don't think enough people have said that. It's easy to be critical of people who are looking to manufacture and forget they too are learning as they go. Building cars is hard, and I like what you guys are doing. The second prototype is looking much better.

The cobalt is a great donor. Cheap and plentiful and the powertrain is solid. I am planning on stuffing one in my daily driver Yaris (if you have a CAD file of the ecotech/trans I would love to have one). Please keep doing what you are doing, and sharing the process. I think you guys are going the right direction, and bet you will have a well sorted car very quickly.

If you opt to cater to the racing crowd, I'd only suggest to make sure drivers can adjust the balance to their driving style and how rough their surface is. Hobby racers will overlook a lot if they can make the car fun to drive at their home track/pad :mrgreen:

Cheers.

_________________
Build log: viewtopic.php?t=9291


Top
 Profile  
Reply with quote  
PostPosted: July 13, 2015, 11:31 am 
Offline

Joined: February 9, 2015, 6:31 pm
Posts: 19
Thanks for the comments.

In reply to wrightcomputing:

We have looked into adding an option to change the rear suspension and will probably try it out in the future. With the low price target we are shooting for, adding control arms, rod ends, shocks, springs, mounts and other hardware would substantially increase the cost of the car. On top of that, it would be slightly more difficult for our customers to assemble, which goes against our goal of making the car easy and quick to build.

As far as looks go, we've received as many comments about how cool the exposed suspension looks as we have comments disliking it. I like it, but I understand that some prefer a cleaner look.

C10CoryM wrote:
I'd only suggest to make sure drivers can adjust the balance to their driving style and how rough their surface is.
Can you elaborate on this please?

Over the weekend we mounted the fuel cell with straps, mounted the fuse block and ECU in the rear, started on the front bulkhead that separates the radiator from the passenger compartment and built up the front suspension. Here is a pic of the front suspension including the CNC machined aluminum steering knuckle (cut from 3/4 inch plate), control arms and shock:

Image

We considered using ball joints at the end of the control arms but ended up going with chrome-moly rod ends. They have a 5/8 inch hole through the ball and 3/4 - 16 threaded studs. The hardware shown is for mock up and will be replaced with the nylon locking variety during final assembly.


Top
 Profile  
Reply with quote  
PostPosted: July 13, 2015, 4:11 pm 
Offline
User avatar

Joined: June 8, 2010, 8:02 pm
Posts: 619
Location: White Rock, BC, Canada
adoyle88 wrote:
C10CoryM wrote:
I'd only suggest to make sure drivers can adjust the balance to their driving style and how rough their surface is.
Can you elaborate on this please?


Primarily adjustable swaybars and shocks. For driving style (especially at autoX) everyone wants a different amount of rotation/oversteer. Adjustable swaybars will be enough to allow people to tweak to suit their wants. For surface, people race on everything from dead smooth pads, to potholed runways. Being able to adjust your shocks and change springs can make the difference between hating an event, or having a blast.

I understand (and appreciate) you guys are shooting for the simple, low-dollar market. I think it makes sense. Just if you opt to cater to racers they need a little more options than the guy who just wants to cruise and try some twisty roads.

Couple of other things you may be totally aware of:
-if your kit is able to use the Cobalt wiring harness uncut, I would advertise the heck out of that. A lot of people get scared of electrical and if you can make it plug and play (even if you had to loop excess wire etc), I'd bet more people would buy. Especially for the market you are shooting for. May not be viable though.
-doesn't appear to be much triangulation around the front suspension so far. Now that your fuel tank is elsewhere, can you tie the front coilover mounts and upper ctrl arm mounts together better?
-are the spacers on the heim joints (upper/lower balljoints) large enough to act as safety washers? Heims in single-shear should have a washer to prevent them popping off if they fail.

Cheers.

_________________
Build log: viewtopic.php?t=9291


Top
 Profile  
Reply with quote  
PostPosted: July 13, 2015, 6:02 pm 
Offline

Joined: February 9, 2015, 6:31 pm
Posts: 19
Those are all things we will shoot to include for the race oriented owners. We are already providing single adjustable shocks on the front with 10 inch springs that can be purchased at any rate you could ever want. We are shooting for a 2.2hz natural frequency on the front with a 275 pound spring but the end user could put whatever works for their venue.

At the rear on P2 we are using Koni cut-a-strut single adjustable inserts. We think this will get us in the ballpark for most courses. Going with the fancier control arm setup that wrightcomputing brought up would definitely allow for easier tuning on the rear but we are going to see how composed the car can be made with the Koni inserts.

With the struts on the rear of the car, the sway bar connects just as it did on the stock car. Aftermarket adjustable sway bar endlinks are available but we might make our own in the future. It is pretty open at the front to attach a swaybar and we can make it adjustable just like the rear.

We do use almost the entire donor electrical system. There are several wires that can simply be cut and removed. The only things that have to be done to the wiring harness are extending some wires. We have found a source for the OEM plugs so we plan to make our own extension cords so that our customers don't have to solder any wires. We will definitely be advertising this when I get time to update the website.

X braces, support hoops and gussets are ides we've bounced between in that space where the tank used to be. Sometimes we like to give some time to think about what to do. The frame is pretty tight there (16 inches between upper frame rails) so it shouldn't take much to keep it rigid. We will keep this in mind as we develop the radiator lower mount.

The spacers on the heim joints do not have safety washers yet but they definitely need them. The spacers and bolts would slip right through if there was a failure right now.

Thank you for the discussions. Reading through suggestions/questions and writing out our own ideas really helps us flesh it all out.


Top
 Profile  
Reply with quote  
PostPosted: July 13, 2015, 6:23 pm 
Offline
User avatar

Joined: December 7, 2012, 8:28 am
Posts: 1411
Location: Sarasota
adoyle88 wrote:
Thanks for the comments.
Image

These uprights are a thing of beauty. I am just about to make my own, here are a few things you could do with it for adjustability.

If you add shims to the bolts on the steering arm you can have adjustable ackerman angle. Multiple mounting holes for the ball joint will adjust the speed of the steering. Doing that will increase the total movement of the wheel though so make sure there is enough clearance.

You can also shim the upper and lower control arm mounts to adjust the king pin angle.

If you rotate the hub, you can use 2 of the bolts to mount the steering arm. Then the are 2 less bolts in the upright. (this would mean slightly redesigning the upright but might be worth it and save cash in the long run on hardware). Maybe you could lower the steering arm to the bottom 2 hub bolts and mount the steering arm ball joints from the top.

Having the adjustability will be good for you guys to get the car dialed in too.

Having upgrades is good for marketing. Then your base kit is $20K but most people will spend closer to $30K after they have all the options. Obviously prices are just examples.

_________________
2015 & 2016 EMod Florida State Autocross Champion
2013 & 2014 DSP Florida State Autocross Champion

Scrap Metal Build Log viewtopic.php?f=35&t=14558


Top
 Profile  
Reply with quote  
PostPosted: July 14, 2015, 11:02 am 
Offline

Joined: April 8, 2012, 7:05 pm
Posts: 128
Location: Warrens WI
Have you guys thought about selling sets of those uprights? I would think you could sell them fairly fairly cheep if you are going to be setting everything up for production for the kit anyway. It looks like it would be simple for you to make the 3/4'' plate and non drilled blocks for the ball-joints (I say non drilled so the buyer can use the ball-joints that they want) Then all the buyer would need to do is buy the wheel hub and make the steering arm for there application.


Top
 Profile  
Reply with quote  
PostPosted: July 15, 2015, 8:33 am 
Offline

Joined: February 9, 2015, 6:31 pm
Posts: 19
Thanks for the suggestions wright. We could definitely make the front very adjustable with those changes.

The hub we use is from the rear of the Cobalt donor and comes with studs that are pressed into it. Those are what you see holding it to our upright. On the first prototype we pushed two of the studs out to replace them with longer bolts to mount the steering arm. The OEM studs were very tight and nearly impossible to remove. Since our customers would have to do this in their home garage, we've decided to leave the stock studs and mount the steering arm separately to make things easier.

pwreimann wrote:
Have you guys thought about selling sets of those uprights?
We hadn't thought about that until now. Maybe we can start producing all kinds of parts for the Locost community once we are up and running. We have received a few requests for fenders and mounts as well.

Yesterday we were able to lift Goblin P2 off of the chassis jig and put it down on its tires (205/55 16 front and 255/50 16 rear). We've got a few more mounts and frame components to finish but we expect to got from roller to driver in less than a month.

Image

Image


Top
 Profile  
Reply with quote  
PostPosted: July 15, 2015, 11:59 am 
Offline
User avatar

Joined: June 8, 2010, 8:02 pm
Posts: 619
Location: White Rock, BC, Canada
Mmmm. R888s.

May want to consider using a spherical bushing for the cobalt lower ctrl arm bushing. I think you will see some serious oversteer on corner exit (and trail-braking?) if you keep the rubber. They can be bought, but I'd guess you guys can fab something cheaper.

Cheers.

_________________
Build log: viewtopic.php?t=9291


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 47 posts ]  Go to page Previous  1, 2, 3, 4  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
POWERED_BY