7740 power functions

[Mikado]

Hello :) 

My mum recently handed me some boxes of old lego that I had as a kid, and found this yellow train 7740. 

It lacked most of the tracks and cables, so I orderer power functions train engine, battery pack, lights, ir rec. and remote controller. I also found some cheap new RC tracks.

Now I have some problems and I registered here as you seem very helpful :)

The train engine cable doesnt fit through the 6x28 base plate, how do you solve this? Drill a bigger hole?

Use a blue 6x28 with the square cut out and spray paint the sides? 

Use a black 6x24 with square and shorten the train? Or cut out the bottom edge and add a 6x4 plate?

Use plates and build an edge with 1 wide plates under it? (I built some baseplates from plates with 2x2 spinning thingy and they work fine but it doesnt look as good, i have alot of plates with pins- do they fit in the technic plates with holes?)

I only had 1 6x28 black base plate, there was also 3 blue ones and 3 6x24 black cheap on bl so ordered them just in case. The black 6x28 looks best of all the options but theyre expensive and feels wrong to drill a hole in it. 

Next problem, there is some weights (2x2x6) with stickers where I had planned to put the battery pack - is there a way to move the stickers from one brick to another? Will i need to put weights somewhere else?

If i want to replace all the old wheels, do i need the new wheelholders as well as the pin and wheels? Are the new wheels best? 

I didnt have time to read everything here so maybe its been answered before, if so a link would be nice :) thanks for reading

[TrainDragon]

You could order a 6x28 with the 2x2 holes from BrickLink, part 92339.  But I just checked a PF motor cable and it fits through the 1x2 hole in part 4093.  Maybe I'm not understanding your problem, but it seems to me that what you already have should work without needing to be drilled?

 

The stickers, you can get replica stickers for the set and put them on whatever parts you choose.  I found these stickers from OKBrickWorks for your set on eBay.

 

[Mikado]

Thank you :) I will order new stickers.

Hmm The cable fits if I remove it from the engine or the 2x2 brick, but didnt look like this could be done? Ill try to take some pictures later, might not be able to do what I want as the battery pack will cover the holes.

[TrainDragon]

The 2x2 brick should fit through the 1x2 opening (sideways).

If the IR receiver, battery box, etc, are not quite fitting in your train, you might consider the new Powered Up version.  The motor connects to the battery box on the side instead of the top, and you won't need to worry about the big IR receiver either as it works over Bluetooth.

I also stumbled onto this site after I posted.  I don't know anything about them but they look like they are based in Europe, which would probably be much faster/simpler delivery than the US one.

[Mikado]

Thank you :)

We do not want an app or the need for a phone/tablet when playing with lego (hoping the kids will have alot of fun with this when they are older), thats why I tought these would be good :) if i cant get it to work i guess we will go with the old system, but the sleeper plates are very brittle and will break everytime a kid want to make a new track. The new RC tracks were really cheap and if (when :p) we buy more trains its nice to have a similar system.

88000, 8870, 8884, 8879 and 88002 are the parts we got. 

Will try to take the baseplate off and try again, did not want to break it and only got half of it in without forcing :/ 

I also saw someone made an amazing Hogwarts Express with walls that could be flipped down for easy access and play, did anyone do something similar with 7740? 

Found stickers on ebay from germany with free shipping for 7€, had no idea so many made and sold these so now I can use different bricks and replace the ones with teethmarks :p 

[dr_spock]

With the less expensive 6x24 black train base, you could add 2x6 black plates at each end to lengthen it to 28.  You may have to extend the couplers further out to couple with the other cars.  Putting the battery box over the train motor will help with traction.  

It is not necessary to use a phone/tablet with Powered UP for controlling trains.  There is a Powered Up train speed remote.

 

[Mikado]

Thank you for great advice dr spock. Didnt know powered up had a remote, but most of the reviews at the lego site are horrible and now we already have the other parts so hopefully we make it work :) 

still couldnt get the 2x2 through the 1x2 (the small connector seems to be a bit taller than it should), so will try with the 6x24, if not we might spraypaint the sides of the blue 6x28. Spending 17€ + postage for one black base is to much in my opinion.

I havent played with lego for so many years and there seems to be alot of new pieces! Maybe there is one like 4865 that can be placed under normal plates? 

[zephyr1934]

The 7740 set is considered a classic. So I would suggest you do not modify the parts. The 6x28 train base that came with it should have 1x2 holes. I'm pretty sure you SHOULD be able to squeeze the PF connector from the motor up through the bottom of one of these holes. It will be tight, but it should fit.

You could also replace the train base with the PF version, 92339. This part in black is stupid expensive, if you go this route it would be cheaper to replace all of the black ones in in the set with dark gray.

In any event, PF is a lot cheaper than the new PowereUP so as long as you have room to fit the IR receiver in it is a good option.

[PeteM]

It is incredibly tight but can be done (with a lot of force). I would not recommend it if you are planning to ever return it to its original state as getting it back out is even more difficult. 

[Mikado]

Hmm think I will buy the expensive one, I want it to look right and it feels wrong to paint or drill holes. I still have 3 blue 6x28 and 3 black 6x24 but those could be used to build other trains. 

I doubt I will rebuild it with the conducting tracks, I didnt recieve the new RC tracks yet but the old ones are very brittle. Also more fun to be able to get more motors/battery packs and add "fantasy/play" trains for the kids.

I was planning on just looking through the lego and build a few sets and suddenly its turned in to a new hobby :p guess ill have to get the 2 extra wagons for this one as well :) 

[Some_Assembly_Required]

do any of you have a 6 x 28 yellow plate? im not trying to mooch im just doing a bnsf loco without buying the thing.

Edited January 14, 2021 by Some_Assembly_Required
the train base was not yellow

[brick-builds]

In my new project I will integrate a power functions motor in the 7740. Here is the first photo, a video comes soon.

 

 

[Paperinik77pk]

On 5/24/2020 at 4:42 PM, zephyr1934 said:

The 7740 set is considered a classic. So I would suggest you do not modify the parts. The 6x28 train base that came with it should have 1x2 holes. I'm pretty sure you SHOULD be able to squeeze the PF connector from the motor up through the bottom of one of these holes. It will be tight, but it should fit.

 

It can be done - with some patience and a bit of wd40/soap/lubricant of some kind. I also modified a 7740 to PF in the past (using original train motor and lights) and it worked fine! 

My 2 cents on the very nice project: 

Central third wheel on motorized bogie:  On the PF train motor and Technic-based bogies  it will work as a fulcrum between the two powered axles, reducing traction.  It is quite difficult to have a sort of "suspension" for central wheel like in the old 7865 12v motor, so I tried to remove traction bands and it worked quite fine.

Position of battery box :  It's always a mess - it should be over the motor to increase traction. Problem occurs when using a PF motor inside the cabin, since it limits the possibility to transmit power to the bogie (the risk is not to respect the internal height). Due to this I came back to the original PF Train motor instead of a more technically interesting solution like an internal motor. A possible solution could be using a 7.4LiPo battery used for drones. Smaller, rechargeable, but it depends on personal taste. It could give the interesting possibility to have two traction bogies, placing motor in the middle and using two cardanic axles (very similar to H0 model trains).

Good work, I'm curious to see how it turns out!!! 

Ciao!

Davide

 

p.s.

I found some photos of the second conversion (motor PF and real 12v wheels - here all with rubber bands) - you can find them here:

https://photos.google.com/album/AF1QipOtQB9uuRU41-NBkJ-5iCYAiahPi0McZsrwp_G0

 

Edited February 1, 2021 by Paperinik77pk
Link to 7740 PF Mod