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Sep 06, 2010, 09:30 AM
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Build Log

1:87 (HO Guage) Mercedes Coach to RC

Hi all, I've been getting back into micro cars since Shin directed me to the members micro rides thread where I saw a 1:87 Horse box converted to RC, this really inspired me to build my own, after a short search on eBay I found, bid and won.....

Mercedes 303 coach

I thought this would be a nice and easy first build, so far it is.

This has a nice flat space under the seats, I'll convert it without seats at first, I'll add them in once I'm a little more experienced. The plan is to mount the constant rotaion modified servo behind the rear wheels, the radio and battery in the middle and the steering servo infront of the front wheels if there is room for it there, if not it will have to go in the middle.

Late on saturday night I had a go at fitting gears and motor from a PicooZ heli, It worked out well.

I also tried the PCB, just as a temp test bed, it wheel spins and spins out (there is no steering yet, this will be the hardest part for me to do) it's way over scale speed, some where around 340Mph mark, I may gear it down but as I am building it for fun rather than true scale use it's good for me.

I have found all the small radio gear and 2 servos, I'm waiting for them to come from china so today I tested it with full size servo PCB as an ESC and full size RX, Luckily the RX is happy on a single 3.7V LiPo, It's working really well, even if for now it is only forwards and reverse 1ch setup, photos and video in the next post.

Untill then here is a link to the photo gallery


Love peace and chicken grease!
Last edited by djdavies83; Sep 08, 2010 at 08:20 AM. Reason: 1st image nolonger laoding, replaced with another
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Sep 07, 2010, 07:04 AM
Hey djdavies83,

nice build. i got your message from youtube. my opinion with your drive gear is to use a worm gear from a cheap toy train or use a servo. if you need help, don't hesitate to ask.

in my video, you can see that i was using the original plastic wheels. but i made a rubber wheels to improve the grip. its really easy to make using a rotary tool.(dremel) I'll make a video of it if i have the time.

good luck with your build and keep it up. I'm excited to see it finished.

keep posting your progress..
Sep 07, 2010, 08:30 PM
We can rebuild it!
djdavies83's Avatar
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Hi Ian, that was a pretty fast reply, Thanks for the kind words of encouragement, here is where my thoughts are with this project.....

My first plan was to use a contstant rotaion hacked servo just as you did, I have two micro servos coming from china for this. I just couldn't wait to get started so I threw the Heli gears and motor in there and wired it to the PCB of a servo from a 1/10 car. I have looked at alot of photos of the worm gear method, mostly on 4x4 and even 6x6 wheel drive German mikro trucks, Mikro is German for micro, I got a lot more results when searching for mikro rather than micro. Sadly as I want to fit the seats back in there would be no space for a worm gear, I may still use the gears as well as the PCB from a micro servo that is on it's way.

I'm guessing the blue plastic of your steering is from left over micro servo casing?
I was planning on building mine from brass rod and pipe soldered into shape but I think I may have to cheat a little on this and use parts from a cheap mirco car, the little bloacks have their own axle pins and and pegs that the link bar and the upper and lower plates (the blue parts in your model) fit over, Ill have to built my own plates and link bar as the coach is narrower than the car I'm taking them off.

Servo pacement is a little bit of an issue for me, as I want to keep the seats I can not mount servo as you have done, next best option is laying flat on on it's side and breadthwise to the chassis but, I think it may be too long to fit.
What I think I will have to do is lay it on it's side and lengthwise to the chassis, with servo horn pointing up this would give the link rod a forwards and backwards movement, just before the link bar I would have to use a small "L" shapped bar with a pivot in it's corner to convert the forwards and backwards movement into a side to side that could then move the steering link bar.
An Idea I had in work tonight may prove the best, thing is, at this scale I think it would be very experimental......
A heavy duty piece of fishing gutt threaded through the inner insulation from some "2.5mm Twin and earth" cable to act like a pull/push rod like you see in model planes, the big old balsa and nitro ones that is. One end of the inner (fishing gutt) to the link bar and the other to the servo horn and the outter (insulation) held to the chassis. Like I say, very experimental at this scale but worth a try even if only for the fun of trying.

I have damaged the front slightly I may try a little plasitc filler and paint over it, I would like to have a go at lighing the seating area, a bear LED would be way too much so I may try some fiber optics or fishing gutt fed from an LED and ran along the ceiling to look like flourescent tubes, I may also go with some along the floor at the edge of the gangway and paint spots over it to look light the LED strips you have it the floor to help you walk in the dark.

Hopefully my servos will arrive this week and I will have found my iPhone after my 2 year old grabbed it and put it somewhere before I woke up on monday morningthen I'll be able to post some new pictures and video of "where I'm at" with this "Mikro Mercedes" coach.
Sep 09, 2010, 06:28 AM
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Ok, panic over and iPhone found, just done a quick edit and upload of the gears being run with a PicooZ Tx/Rx setup.

1:87 TTTT Coach build log (0 min 52 sec)

As you can see at the end of the video the plastic wheels don't do a great job if keeping it in a straight line at speed, I'll try the rubbery feeling spay on plaster a try, If that fails I'll be asking Iancesar for more info on how he made rubber wheels for his Politzia horsebox.

Coach next to 27 Mhz Tx

Temp 27Mhz setup, waiting for micro RX and servos (no steering yet)
Last edited by djdavies83; Sep 09, 2010 at 10:26 AM. Reason: add images
Sep 10, 2010, 03:36 AM
We can rebuild it!
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Did a little experimenting with reusing (cheating with) steering parts from a old, cheep little 1.2V NiCd/NiMh car I bough for £2 a year or so back, wish I bought about 3 or 4 for that price. 

The coach is narrower than this little car and it also needs a better turning radius so it will need it's own plates and link bar made up, I used some thin plastic pretend credit card to help me find just the right size and spacing for my parts. 

This little experiment showed me that in order to the the wheels the same distance apart I would need to make the plate holes 13mm apart, 12mm was to small and 14mm was to big so, well, you do the math.

I reall want to get stuck in, make the real plates and link bar and get them mounted but, untll my servos arrive I won't know where I will mount the steering servo and if I start removing plastic I may remove too much and either make it really difficult for myself or kill the whole project so I guess I'll have to wait.  
Sep 10, 2010, 04:16 AM
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Current 27mhz setup.
1:87 Coach build log 27mhz tests (2 min 10 sec)
Sep 27, 2010, 12:45 PM
We can rebuild it!
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Steering into trouble.

Well, micro servos arrived early last week, thing is even at about 22mm they are way too big to fit infront of the front wheels, or behind them, or anywhere else for that matter.

If I were to try and fit one in the same way as ianceasar did on his horse box I think that with how much lower the floor pan is on my coach ground clearance would be an issue, I would also have to forget about refitting the seats and having the passenger compartment clear.

I made a cardboard mock up of an even smaller servo I found on eBay. 

Even though it's a fair bit smaller and the output spindle would be almost dead center It would still be a little too big for the front but I may get away with mounting it sideways behind the front wheels but to be able to mount it there I would have to make some clever link rod or pull pull fishing gutt system. 

Before I found the smaller servo I bought a pair of these tiny linear servos,

I'm not sure if one of these will be small enough to infront of the wheels but it should be a good size to fit behind the wheels and under the seats moulding, I'm going to connect it to the steering rack with something flexible, that way if the servo has a greater throw than travel of my steering rack the connector will flex and eliminate the chance of damage.

Progress on the steering plates and rack to come on the next post.   
Oct 06, 2010, 09:05 PM
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The micro aileron linear servos I ordered from eBay user Abeyerr arrived on Saturday, they really are tiny!

Here's one on a 10 pence piece/American 1/4 Dollar

Thing is, on route from china the inner plastic tray that they were shipped in got a little crushed at one end...

Typically, out of the pair it's the one that fits the best that got damaged, I contacted Abeyerr who instantly offered to send a replacement free of charge, of course I'll be waiting about 10 working days for it but as I have a damaged one I can build my steering rack to the correct size and shape, then simply swap out for the working servo when it arrives.
In the mean time here are some photos while I get on with building the rack.

Once I trim off the little lugs closest the to wheels and cut the horn down to it's lowest hole, the block where the horn slides back and fore in will fit behind the steps.  

I'll need to trim away section of plastic under the driver, he will end up sitting over the motor that moves the servo horn. 

The lugs I mentioned above can just be seen in this photo, I bought this picture hanging set because the metal is brass and it only cost £1 so I'll be making the rack out of these and using a turbo flame cigarette lighter (also from a £1 shop) as a blow torch to "weld" the pieces togeter with solder, This idea performed well when I tested it.

At this point you may be thinking I'm a pound shop junkie, you would be right!
Oct 10, 2010, 06:45 AM
We can rebuild it!
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Linear servo on 1:87 RC coach (0 min 33 sec)

Just a quick one showing a 1.5g micro linear servo in place on the 1:87 coach I'm converting to RC, these servos are usualy sold as a pair of left and right and used for aileron control of sub-micro indoor planes, I got them from Abeyerr on eBay, just under £7 Inc free postage, they came in less then 10 working days but the right servo, the one that's not in the coach was damaged in transit, i contacted Abeyerr who instantly offered to ship a free replacement, I would have just used the left servo bur as it's a mirror image of the right it will not fit as well.
Oct 11, 2010, 09:57 AM
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Steering is racking my brains

So tired in work yesterday, I was up till 5:30am after a series of trial and error attempts at building the steering rack, I finaly got some solid work done, my earlier idea that the steering block pivots should be 13mm apart was off by 2mm, they should have been 15mm, here's a photo run down of late saturday nights progress....

This is a failed attempt to drill two holes dead centre of this brass picture hanger, the paper next to it is the start of a template, I made it by folding it on it's X and Y axis to get it's size, shape and hole spacing perfectly symmetrical, the four wholes are 1.5mm, the outer two are 2mm for the block pivots and the one in the middle is just to mark the middle.

Paper template taped in possition on a fresh piece of brass, it's a little wonkey in this photo, I corrected it before cutting and drilling.

Brass plate resting on the underside od the chassis, next to the coach is my stock micro Veyron just for size comparison. I got a little too close when trimming down the brass plate so I used it as a template and made a new blue plate from the bottom of a micro servo I'll be using as an ESC for the rear wheels.

Here's the blue plastic plate fitted, it was at this point I realised I had made some misstakes, I had to trim away more chassis for the blocks to be able to pivot properly, but then there was nothing left for the 4 screws to go into so that center hole came in handy, of course one I had it screwed in it was clear to see the blocks needed to be another 2mm apart and a 3rd version of the plate was needed. Behind the chassis is the door off an old VHS tape to be used as donor plastic for the larger 3rd version of the plate.

New black plastic plate cut, you can also see the 1st and 2nd versions of this plate. 



The remaining tasks for the steering:-
  • Make top plate and mount to chassis.
  • Make rack/link bar between pivot block. 
  • Find exact mounting position of servo and screw it down. 
  • Make flexible link between servo and rack/link bar.
Oct 15, 2010, 08:44 AM
Hey djdavies83, you've got good progress in your build. I haven't been in touch for a while cause i got busy with my job. i was really having fun watching your vids. you have the fastest bus on the planet! and it drifts. haha. really nice.

and i envy your micro servo. i wish we already have something like that locally. if my schedule permits me tomorrow, i will show you how to make those rubber wheels. i will share to you some of the links that i had when i was building my truck. its where i got some of my ideas and inpiration.
Mikromodellbau - Vorderachse 1:87 MAN 5to LKW (0 min 13 sec)

keep on posting.. good luck..
Oct 16, 2010, 09:11 AM
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djdavies83's Avatar
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Hi ian, thanks for the encouragement!

It will be great to see how you made rubber tires.

I think the micro linear servo for my steering is not as fast as yours, I love the steering system in the video you showed, I was trying to think how to steer with the servo moving back and fore rather than side to side.
I think I may have been on one or two of them sites but when I have a free hour I'll sit down with a pc and look at them all, most of my posts come from my iPhone, it takes the photos and uploads them to my photobucket account, I write my post in the e-mail app, copy and paste the [img] codes in then copy and paste the whole thing into and hit post!

All done in little bits here and there,
wherever I have a few minutes to spare.

Haha, i'm a poet and I didn't know it!

Anyway, enough about the iPhone, it's had more than enough hype over the last few years, back to the model!

After spending about 5 hours on my steering I have been tented to buy a ready made one...

I'll have one more try at building it myself before I give in and buy the one in the photo.

One thing about me is that I can never fully complete one project before thinking of even more projects, I have another Mercedes coach and a MAN city centre type bus, it has low floor so all the electronics will be seen through the windows, the new Mercedes comes apart easily and clicks back together alot better than the one I'm currently working, "I have a cunning plan" for to keeping it closed, I'll reveal that in good time.  Untill my next post here are some more photos.

Nov 05, 2010, 09:29 PM
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Ok so I folded, I went and bought this steering kit,
I went for the one without wheels for two reasons, I thought it was assembled with the wheels and it was no cheaper buying wheels and kit together, so I only bought the set. 

I have also been looking into casting my own purpose built silicone tires for this bus, my first google search took me to everything here looked like it would work well for me..... I looked up the bill of materials and was severly put off this method! A couple of weeks ago I asked a technician from the theatre over the road from my works place his name's Beasley, like quite a few of them he also makes props for stage and tv, he made a telephone safari hat thing that was in the mighty boosh. As luck would have it his partner did her dissertation in silicone moulding and he told me to look for dental alginate, I found this to be alot cheaper than the stuff mentioned by oldweirdherald's "tire casting 101".

Last night I did a little more searching and found silongies page on oldweirdherald.
I really liked the look of this method and started searching the black silicone that was used...
it's for sealing gaskets in engines, at £7.55 + p&p it was a little expensive for my liking so I looked an alternative,
I found "No Nonsense Sanitary Silicone Black 310ml" for £1.75 at my local screwfix, this should all work out just fine, now I can try both methods and not worry about the cost! I think I may have to make my own wheel hubs, with the double wheels on the rear, I will most likely try and cast them together as one tire.   
Nov 06, 2010, 01:59 AM
Inventor&Genius Extraordinary
tune by tito's Avatar
you can try electrical silicon tape, use bicycle repair tube glue to vulcanize the rubber together then with hot knife trim the side and make some thread in to the rubber, some cheap chinese electrical tape is very rubbery, find some and try.

Best Regards Tito
also I'm waching you progress.
Nov 06, 2010, 09:36 AM
We can rebuild it!
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Hi Tito, most of the insultating tape I've used has been PVC but I'll deffinately try that out if I come buy any rubbery tape, I remember back when I was a kid I  did my 1st handyman work fitting a new cable to a satelite dish, I used something I think was called self amalgamating tape, it was quite rubbery and stretchy but I think it would be to thick if the wheel ain't trimmed down first. 

One idea I had before ianceasar mentioned about making rubber wheels using a dremmel (still looking forward to seeing that) was "spary on plaster" a clear rubbery spary used when a conventional plaster won't stick to you, it looks like I'll have to start another thread that purely about small scale rubber wheels. 

I noticed your into micro and nano planes, you know any any cheap 2-4ch  recievers, IR, 27MHZ or 2.4GHZ just want something really small and cheap. 

Thanks Tito.   

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