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R/C Bedford TK Tipper 1:43 and 4mm ACE Ergomatic 6 x 4, 4mm Landrover


Giles
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I know this has been done many times, but I thought I'd have a look at it.......

The donor vehicle (well, the front end...) is the Bedford TK, and the brass chassis will be grafted on to it.

I still have to sort space for the traction motor. I used Mod 0.4 bevel gears in order to make space for the tipping mechanism, which needs to be as low as possible in order to get some mechanical advantage on the pivot.

The tipper motor is a 6mm diameter 60rpm gearmotor from ebay, driving an M2 shaft.

 

 

Edited by Giles
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I've had to squeeze a motor in the space that's left after fitting the tipper mechanism. There's no room for my usual N20, so I fitted the lovely little 8mm diameter gear motor that I also fitted to the Mechanical Horse. I was worried that it wouldn't be strong enough - but it is! 

It also necessitated the use of a cardan shaft,  so I made UJs form 3mm tube and 0.7mm NS wire, as per OtherPlanet's method.

 

 

There's no RC yet - this is simply a test to make sure the transmission works.....

Th

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  • 2 weeks later...

I know the occasional lorry isn't to everyone's taste - but never mind!

 

I have silver soldered the tipper body frame together, with the opening tail-gate. (MDF drop-sides and headboard timbers)

 

 

The tail-gate should of course lock when down so that the load doesnt get spilt. In reality this is of course a manual operation, but for RC, this is going to have to be an automatic mechanical system. So...... the tailgate is held closed  by a pair of pivoting latches, which are operated by a rod forward on the tipper frame. This terminates in a bell-crank, which, when lowered hits a block or plate, and forces the catches to rise and trap the tail-gate. It actually works as well.....

 

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2019-08-17_06-59-39 by giles favell, on Flickr

 

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2019-08-17_07-04-12 by giles favell, on Flickr

 

48560075677_afd62e8707_b.jpg

Rc tipper by giles favell, on Flickr

 

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  • 2 weeks later...

Sorry for not having  commented earlier on this developing work. (Have been away on business and holiday)

Lovely job as usual Giles, I particularly like the tail gate release, I have been contemplating the same problem, and your solution is particularly neat.

 

 

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As a small aside, it was a nuisance having throttle and tip on the same stick (as can be seen on the video) as it was all too easy to nudge the vehicle forward when tipping.

The cure for this was very simple. Cutting a cross-guard from plastic and gluing it in! Very much easier, and works every time!

 

48659413883_6603ed85fd_b.jpg

TX Cross-guard by giles favell, on Flickr

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5 hours ago, Giles said:

As a small aside, it was a nuisance having throttle and tip on the same stick (as can be seen on the video) as it was all too easy to nudge the vehicle forward when tipping.

The cure for this was very simple. Cutting a cross-guard from plastic and gluing it in! Very much easier, and works every time!

 

4 hours ago, asa said:

Stunning work Giles.

I say, that's a little bit excessive for such a simple task... ;)

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I've made a little 4mm TK, just to see if I can get  the same characteristics, and it's been a success. I've used the little K20 motor, and got a 180mAh battery under the load bed. This one does NOT tip, as it's quite a small vehicle, and there isn't really room.....

 

 

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Oh no....... I shall complete the twin to this one and leave it (I need two as the operational duration will be insufficient. 1 in use, 1 on charge....). I did the TK as a  direct comparison to the 7mm version. just to see if the techniques were transfereable to the smaller scale (drive and front axle) which they appear to be.

 

This is what the exercise is about ( the 4mm tipper is still awaiting its correct battery here, hence having a strange battery in the cargo space!)

 

 

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On 20/11/2019 at 19:22, Giles said:

I've made a little 4mm TK, just to see if I can get  the same characteristics, and it's been a success. I've used the little K20 motor, and got a 180mAh battery under the load bed. This one does NOT tip, as it's quite a small vehicle, and there isn't really room.....

 

 

Fascinating stuff, amazing! I took a look on eBay for K20 motors and they all seem to run mega fast. Do you have any particular supplier?

Cheers

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Hi David,

Having just spent an hour searching, it would appear that no one on EBay is selling the appropriate type any more! A lesson to us all to stock up whilst we can.....

 

There are still the 10mm diameter 120rpm gearmotors with the plastic 'star' output shaft. I have successfully fitted the larger nylon bevel gears to these (either the Morris J or the Land Rover has this arrangement - I can't remember which). There is also a range of 6mm dia gearmotors which would do for 4mm models. These would not be anything like as powerful as the 8mm, but should be adequate. I have not yet tried them for traction, but I have just ordered a few 100rpm (@ 6v) to see how they go. It is certainly possible to fit the small Mod 0.3 bevel gears to these using Devcon epoxy, as I've done it.

 

Shame about those K20's - they are superb - if I ever see any pop up, I shall be buying them! 

 

Edit. Morris J  with components. 10mm 120rpm gear motor fitted with nylon bevel gear.

 

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2019-03-12_05-22-14 by giles favell, on Flickr

Edited by Giles
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The Austin 7 completed. I have a small stock of my favourite K20s, but I shall have to ration myself, and use other gearmotors where appropriate. Such is the way of things! However, it also means that doubtless other hood things will come down the supply chain!

 

 

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All my axles are scratchbuilt. First by hand, and then I worked out how to CNC them on my Stepcraft - but in the last 12 months I've developed a way of laser-cutting all the components (building them up with Plastic Weld) with the addition of wire for King Pins and track rods...... They come out quite compact, with decent geometry. It took quite a lot of experimentation to crack it reliably. The 4mm ones take 1.5mm I.D. flanged bearings (which require a 4mm dia. recess in the back of the wheel and the axles are 2.4mm deep at the clevis. The Bedfords have an 18mm dimension between king-pin centres, but I can make them any size (within reason!). The 7mm versions take 2mm I.D. flanged bearings and are 3.2mm deep at the clevis.

 

I'm considering making them available (not sure whether built-up or kit including bearings) but they're not going to be as cheap as some, simply because of the very low quantities involved and the time it takes (even going to the post box of post office with one package takes some significant time and disruption)

 

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2019-10-16_08-49-08 by 4mm TK axle by Giles Favell, on Flickr

 

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1:76 TK front axle by 4mm 18mm axle by Giles Favell, on Flickr

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For my front axles I have bought from KKPMO in different widths - typically 20mm for a modern lorry, measured between the outside faces of the hubs. As a company, they are so awful in every aspect that I wont buy from them again, which is a real shame as the product is excellent. I have bought from MCC Model Car Parts in Holland, which I think ultimately are the same product from a different supplier, who are at least able to supply the things in a semi-reasonable time. The main issue is that the axles they supply are too short for the bigger lorry wheels. I just glue the wheels onto the end of the brass stub axles, and they rotate inside the plastic hubs, which ultimately is going to wear out. Using bearings is a much better solution as long as the wheels are big enough (I'd probably have to keep doing Land Rovers and Transit vans the current way)

 

I did try to 3D print my own axles, but this basically failed at the first hurdle because I bought a cheap 3D printer that's no good. I have had results printing a 225:1 ratio gearbox though.

 

I'd certainly be interested in using axles of your construction :) 

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  • 1 month later...

Having finally got various jobs out of the way, I've completed the second 4mm Bedford TK, which has been lying in bits without a receiver for a couple of months....

 

All complete now, electrics done, battery fitted, mirrors made and fitted, so I now have a matching pair (one in use - one on charge)

 

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2 off 4mm scale radio controlled Bedford TKs by giles favell, on Flickr

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