My RWD solid axle front engine Escort MK2 build

[Frederik]

Small update! I made a new front beam, the aluminum one was not far forward enough to bolt the skid plate to it, so I made one out of steel. It looks much nicer too, but quite heavier than the alu one, so I drilled some speed holes in it Might drill more on the part facing down to remove some more weight.

 

 

 

 

Now that I think of it I should have tried to do dimple holes to add strenght! Not sure how I would do that though I have never experimented with that.

 

 

I also cut the mock up steering cables at the servo to start and think of how I'll run these to the back where I want the servo. I think I will make them go through the firewall as low as possible (like the one on the right in that engine bay pic, just above frame rail), and run them near the door sills.

 

 

 

This is where I want the servo, with the servo arm poking up through the floor. It will have the two cables attached to the same servo horn hole, one coming from each door sill. Hopefully the added curves in the cable to get there do not induce too much steering slop or friction.  

 

I'll have to think of a way to keep the servo clean (probably a rubber balloon?) given where it is. I don't pan to go through water but certainly some dirt!

 

I wanted to do more but got interrupted. At least I can now put the body on and have the steering bolted, without a big clamp up front lol!

[Oh How Original]

On a note of the rolling over, to be fair you're using slicks on tarmac, it's going to have lots more grip than some knobblies and gravel (assuming it's going to be run like a rally car?) so grip roll won't be an issue at all

[Frederik]

Very true! It will want to slide around and not roll over, which will be wayyyyy more exciting  I want to have as much steering lock as possible (in order to control the slides the best I can!) so I will use a hole slightly farther on the servo arm.. Hopefully I will not overstress the steering servo, it is a fairly fast but not all that torquey servo I think. It is a Hitec HS-5625MG, I used this servo model to steer my Kyosho MP6 1/8 nitro 4wd buggy, so I guess it will steer this little 2WD with tiny wheels no problem!

Edited June 21, 2016 by Frederik

[Oh How Original]

I think your aim for the servo is going to be as fast as possible rather than torque, so hopefully the Hitec will be enough, having not checked the specs lol.

[Frederik]

Yes speed will help save it quickly when the locked rear axle makes it snap oversteer!  I am not a servo spec expert as I never remember what spec value is fast, torquey etc.. But this one is supposed to be a faster one, and the fact I use a fairly long servo arm will make it even quicker, so I think it should be pretty good! And it is strong, based on the fact I use the same model servo on the 8th scale buggy steering, so it will likely not break from trying to extract too much speed out of it

 

Here are the specs:

 

 

Specifications

Motor Type:	3 Pole Ferrite
Bearing Type:	Dual Ball Bearing
Speed (4.8V/6.0V):	0.17 / 0.14
Torque oz./in. (4.8V/6.0V):	110 / 131
Torque kg./cm. (4.8V/6.0V):	7.9 / 9.4
Size in Inches:	1.59 x 0.77 x 1.48
Size in Millimeters:	40.39 x 19.56 x 37.59
Weight ounces:	2.11
Weight grams:	59.82

 

[twisty]

Super work,keep going

[Frederik]

On 24/07/2016 at 16:29, twisty said:

Super work,keep going

 

Thanks twisty! Sorry for not updating recently, been busy with moving house, all for good since I'll have a bigger RC place in the new garage, just need to finish some more work on the house. This has to be one of the slowest longest build ever lol Well the big Subaru on the wall is even longer but it does not quite count since I have not touched it in like 5 years haha

 

[Frederik]

I have a small tiny wee update! I was able to make use of the new hobby space a bit tonight. No huge progress but I started to work on replacing the tiny steering cables I used for testing with actual length, desolder the cables, but then I could not find where I put the solder flux when moving... 

 

So I moved on to other things I have been pushing for a while and proceeded to replace the little m2 screws and bolts holding the chassis rails to floor with larger M3, threaded in the chassis rails. Don't need bolts anymore, and the button heads are inside the car, so they are flusher inside, and I ground the other end flush under the chassis. Nicer!

 

 

 

Then I found the flux paste so I was able to resume working on the steering. I cut the yellow sheat to correct lenght, and made mounts for the steering servo. Here is where I am at now, with the button head screws on the floor instead of bulky bolts and nuts, and ready to do the thingy that will tie the cables to servo horn. That might be tomorrow night

 

 

[Frederik]

Last night I continued the steering in the rear (lol strange to say!) I made two blocks, with one small hole halfway through, size of the sheat, and another tiny hole going through just the size of the cable. This acts as a sheat stopper, so I had the cables arranged like this:

Then I prepared the soldering of the cable to a metal plate I can attach to the servo horn. I did not expect what happened next, maybe you can figure by looking how it is before soldering

.....

The metal plate soldered to the floor... lol  I ground the hole larger to make a bit more room.

My problem at the moment is the cable moves horizontally and the servo arm moves as a radius so it moves up and down throughout the travel... The cables won't flex to follow this so I need to find a way to have the servo horn.

[Frederik]

Made a vid in the garage, it is painted plywood so it slips wayy to much... kind of hard to have the suspension work when there is no grip. It is quite a handful to drive lol especially since the place is not all that big, can't get much speed before hit something lol

Oh and the bumpers are not there anymore since I hit something and they fell all three lol they were held with a dot of hot glue each so.. yeah

 

 

 

I did another vid this morning, slow motion of the suspension when dropping the car on the table from a few inches. Probably need to replace the pistons in the rear shocks for a bit more damping, and also the rear axle linkage touches the steering servo so it kind of bottoms out weirdly, but otherwise pretty good!

 

 

Edited November 27, 2016 by Frederik

[bieomax]

Would it help if the wires werent soldered in situ but more of a loop (thinking like them circuler/ring electrical connectors which have holes in) on the end of each side and then a bolt/pin on the center plate which they are attached.

so when the plate moves off centre due to the servo movement the cables will have an axis to move on.





Sent from my HTC One M8s using Tapatalk

[Frederik]

Thanks bieomax for the idea, yes it would help cancel the vertical movement, but I think I overestimated that problem and it now seems pretty good even with the wires as is. Most important is to set it up so it is at perfect height when completely turned to either side, because when centered there is more wire lenght to soak in the height difference so it is not an issue. Soldered is kind of a hassle because it is not possible to undo anything easily, but it prevents slack from adding up and it saves a bit of space too.

Edited November 27, 2016 by Frederik

[Tamiyacowboy]

one ball joint on the steering bar the wire is solder to. one ball joint on the servo arm and a linkage rod.
ball joint link will travel i somewhat a horizontal motion and not a sweeping circular like the servo arm .

 

so we have a ball joint on the servo arm like a standard linakge rod setup. and a ball joint on the steering cable clamp. as the servo swings left and right the angluar motion is more horizontal due to the ball joints beaing able to rotate in the cups  . it keeps the steering cables in a somewhat more horizontal travel and still gives the push me pull me on the cables.

the weight balance is perfect as seen in the drifts the chassis is holding, its got chassis roll but the weight distro is just perfect , counter correct the drift and the chassis pulls out like it should 

[Frederik]

On 28/11/2016 at 13:13, Tamiyacowboy said:

one ball joint on the steering bar the wire is solder to. one ball joint on the servo arm and a linkage rod.
ball joint link will travel i somewhat a horizontal motion and not a sweeping circular like the servo arm .

 

so we have a ball joint on the servo arm like a standard linakge rod setup. and a ball joint on the steering cable clamp. as the servo swings left and right the angluar motion is more horizontal due to the ball joints beaing able to rotate in the cups  . it keeps the steering cables in a somewhat more horizontal travel and still gives the push me pull me on the cables.

the weight balance is perfect as seen in the drifts the chassis is holding, its got chassis roll but the weight distro is just perfect , counter correct the drift and the chassis pulls out like it should 

 

Hey TamiyaCowboy! Sorry for the late reply. I tried to make a link with the same idea you suggested, except it was a simple link with two holes and bolts instead of ball joints. The problem was with the link lenght I wanted to have (in order to have the servo hidden underneath) the link was so short that it did not cancel the vertical movement all that much. As soon as the servo would rotate, the link would become angled quite a bit and not very effective because it would push and pull the cable attachment down and up instead of left right.

 

So I ended up with direct attachment to the servo horn. The cables can take it and it seems to work well. I tried it a couple more times, had a few screws coming loose lol The car is not all that ready to drive since I did not tighten everything up really. 

 

Weight balance is even better now, with the 2S saddle pack battery, one cell placed on each side of the driveshaft tunnel. And the front back distribution is about 50%, which is what those car have, approximately. I think I will wash the floor a bit to remove the dust which I think is why the car slips so much. The first few drifts were easier to manage when tires were still clean, but dust built up and it starts slipping like crazy! lol

[Frederik]

I did not do much progress lately, but I do take it out from time to time for a spin (I think that's the right word lol!)

 

I accidentally went over an angled cardboard and was surprised how easy it climbed right up! So I did it a few more times on a video

 

 

 

Edited January 28, 2017 by Frederik

[Noj]

French Canadian??

 

Seems to go very well....Much more to do before completion?

[Frederik]

16 hours ago, Noj said:

French Canadian??

 

Seems to go very well....Much more to do before completion?

 

Yes french Canadian  How did you know, is it my profile info, or my two little boys playing and speaking french in the last vid? I did not listen to the sound when I edited the vid, I just cut the video where I wanted so I'm not sure if I talk or if they talk during the vid lol!

 

There is quite a good checklist before completion! Thanks for asking, that will help me put on the table what needs to be done! Here is what I think of :

 

- Find something to cover the front wheels holes in the floor and firewall. Needs something just the right rounded shape, best would be tin can so I can solder it, or worse case I can use some plastic and jb-weld it in there.

- Re-do the passenger side strut, make it same as other side (machine the bearing holes better, no slack)

- Fix the driveshaft (it is too short, I made an add-on piece but need to attach it permanently (currently duct tape)

- Do a better version of the lower 4-link mounting points at the chassis, the little pieces hang too low and I need to find a better way

- Finish the front, the thing holding the lights is held with magnets, make actual brackets

- Route the steering cables somehow so they are not everywhere like currently (might do a roll cage and run the cables along it, but I need to figure out a way of soldering a roll cage, I don't have what is needed to braze, I just use solder)

- Solder the 4-link boxes to the floor instead of having them bolted (I'm afraid of melting the surrounding solders though..)

- Make a cross brace at the front of the 4-link boxes

- Find a way to prevent the top struts pillow ball from moving around inside of their metal holders

- Powdercoat all chassis parts in white

- Paint the body, attach the working headlight correctly to the body, attach the bumpers, wing and auxiliary lights up front.

 

Things I've have in mind for a while might decide to do sooner or later:

 

- Modify how the rear shocks attach to have them poke through the floor a bit, so they don't hang that low under the car. As they are now chances are I'll hit a rock and rip them off... I'll also be able to have more travel that way. I would have liked to have them outside of the frame rails like 1:1 but I made the frame rails a bit too wide.

- Make the front brakes functional. Currently only have rear brakes (ESC). I have the calipers and discs ready (from an 8th scale bike), I need to make them work with the front struts. Not much space is available, especially with my favorite wheels (the m-chassis mini wheels). I'll need to use the larger 4-spoke wheels if I want to do that.

- Install the servo potentiometer at the front, attached directly to the steering rack, so the slop in the cabling system is eliminated. The steering works good now but there is some memory steer (if you turn left, then go straight, it keeps pointing slightly to the left and vice versa).

 

There is more to do but this is what I am thinking of at the moment

Edited January 30, 2017 by Frederik

[Noj]

Only a weekend's work then.....

 

As is often the case, the kids were to blame.....There was a distinct 'Papa' that gave the game away, bless 'em. 

[Frederik]

On 2017-01-30 at 13:12, Noj said:

Only a weekend's work then.....

 

As is often the case, the kids were to blame.....There was a distinct 'Papa' that gave the game away, bless 'em. 

 

Hahaha yes I guess Papa gave the name pretty good

 

 

I got the car to my office where we have a precision scale and it now weigh in at 4.3 lbs, functional with battery and all. Also there are larger areas of carpet at the office, more grip and speed which is scary with this car since it currently has pretty soft suspension and higher CG!

Also removed the oil from the front struts as it was way too thick, makes more sense now but slightly bouncy lol will have to find lighter oil. Made a small vid too, tried to follow the car with the iPhone while at the same time driving the car... I am getting pretty good at driving it but with the camera the skillz dropped significantly lol !

 

 

Now I am thinking of doing a roll cage but unsure how. I have brake line and a bender, but only have stuff for soldering, no brazing. Might give it a go since it is not going to be abused like a rock crawler, should hold pretty good. Searched for some reference pictures to have ideas:

Edited February 18, 2017 by Frederik

[bieomax]

Ive had a bit of a go with brass tube from b&q and standard solder, and as long as you use a seperate flux paste it was pretty strong.



Sent from my HTC One M8s using Tapatalk

[Frederik]

Thanks, good to know, where do you typically find brass tubing in that size? Edit: just re-read and saw you said b&q, I looked it up, did not realize it was a place Might try that out instead of regular auto brake line. 

 

Edit 2: just ordered a bunch of 4mm brass line (I googled that and the diameter for roll cages tube is 38mm, so in tenth scale would be around 4mm!). Ordered 10 tubes of 300mm x 4mm (3mm internal) and one of 3mm (2mm internal) so I can put a piece inside in case I need to make a tube longer. Think is I ordered on ebay from china so it'll take likely weeks to arrive...

Edited February 19, 2017 by Frederik

[bieomax]

I look forward to seeing how you get on with it.

I want to make a crawler/rock racer sort of thing with mine but finding the time to even start designing is a struggle at the moment.

Have you some brass sheet too? Mine you only one of them frames have some infill bits.

Sent from my HTC One M8s using Tapatalk

[Frederik]

No I have no brass sheet, only steel sheets like the floor. I would like to do the inner rear fenders with some sheet, under the rear side windows area. And in all the reference pics above you can't see the trunk from the inside, maybe I'll try to replicate that too.

 

Not sure where I would find brass sheet? I'm in Quebec, Canada, and can't order on that site mentioned above. Wondering if brass sheet is much lighter than the steel I use for the floor which comes from thin air ducts? I used this:

 

[Frederik]

The other night I noticed quite a few type of cans (brake cleaner, compressed air can) have their top area shoulders really rounded, it looks like it would be the perfect radius, and it is steel, so I think I got my solution for those front wheels holes in the firewall, just need to empty a can, cut it and solder it in! No pics of that yet though, it is just at the idea stage for now.

Last night I made a significant change in direction, in steering direction that is I took a servo and put it in front of the motor and it looked as if it could somewhat fit with a linkage going under the motor. With the cable steering having quite a bit of memory steer (does not return to center exactly) and lots of force and speed loss in friction moving the whole thing, I thought it was worth it to try.

The servo is reeeeally close to the inside of the hood, like half a millimeter. Same goes for the distance between motor and the end of the chassis. Pure luck that it fits It is easier to drive since I am able to use 100% of the available steering rack travel, whereas the cables were not able to pull all the way to the ends. Also quicker steering and more precise, I think it will be worth it, and I won't have to tuck those cables around inside the car (and I could not make tight turns with them too..) It is uglier, but I like the added driveability. Someone suggested I should fit a low profile servo so it does not poke as high and I could hide it with a radiator. Might happen at a later time.

 

So all in all pretty happy I made the move, even with all the hours invested in doing the cable setup.. The steering linkage is just a piece of autobody sheetmetal cut to shape with two small holes for M2 bolts. The thing is getting pretty complicated to pull apart now though lol Motor, steering mechanism and servo all crammed in the same spot.

 

Quick vid showing the new setup:

 

 

Also when it was still working with the cables, I did not document it but experimented with relocating the potentiometer from the servo up front, so the servo sees the steering rack position instead of the servo position at the back. I was hoping this would eliminate all the memory steer. I made a test with a cheap servo (to avoid hacking a 100$ servo for that lol!), it kind of worked but the servo was so weak it could not even move the steering rack by itself so I dropped the idea, not wanted to sacrifice a high torque servo.

 

It was quite interesting though, found a neat way of rigging the pot to the front steering rack, drilled a hole in the pot shaft, put a very small tube inside it, and a small wire that is allowed to slide inside the tube, so it can transfer the lateral movement to the pot without binding.

 

BTW in that video the high torque servo is still using its internal pot, I was just testing the pot mounting.

 

 

 

Edited March 31, 2017 by Frederik

[bieomax]

Keep up the great work Frederik, i really enjoy seeing what your doing on this build.

So are you keeping the servo up front ? If so could half of it be hidden with a bonnet/hood slam panel and the other half dressed up as if its the radiator?

Sent from my HTC One M8s using Tapatalk