Jet Hopper Simple Modifications And Upgrades

[Live Steam Mad 17]

Last of the pic's showing the modification.

ARG.

[Live Steam Mad 17]

Next step was to put the rear wheels back on after first ball racing the back axle. Here we go!

My bearings turned up from Hong Kong, they are 8mm OD x 4mm ID x 3mm thickness, and 7mm OD x 3mm ID x 3mm thickness. The former are for ball racing the rear axle, the latter are for ball racing the Spur gear, like Mark has done. The larger bearing is a nice press fit into the 8mm hole that I drilled into the rear axle's bearing seat (as described above) where the original plastic bearing was. I drilled exactly 8.00mm and the bearing is 7.98mm diameter. However the plastic bearing seat springs back after drilling a little bit making for a nice press fit so I took one of these bearings and press fit it into the hole, by hand. It was able to be pressed in so that it protruded just a tiny fraction of a mm. You have to be carefull when pressing in bearings that you don't damage the metal bearing cage (shield), so check for low friction ease of turning after you have finished press fitting the bearing.

Next there is the problem that the rear axle is 4.05mm and the bearing ID is 3.96mm. So I had to use P400 Silicon Carbide and abrade the end of the axle for about 30mm until it would enter the bearing. The rear axle had the very end expanded very slightly due to me hammering a punch into it to remove the rear wheel. I abraded it by turning and sliding the axle, so as not to create a flat on it. It's hardened and ground steel so it took over an hour to do this whilst rubbing quite hard on it with the abrasive sheets. At least you can be surfing the web at the same time LOL.

Then you keep trying the rear axle in the bearing until it slides in to where 23.5mm length is protruding from the bearing. Once you have abraded one small section to where it slides in, don't abrade it any further, just move on to the next section. It should be a tight hand press fit to slide the axle into the bearing, approaching the 23.5mm point.

At this point I noticed that the large (slow) gear on the rear axle was rubbing against a plastic ring on the inside of the plastic gearbox. It really needs a thrust bearing. So I found that you can press fit by hand a standard Tamiya sized 1150 bearing into the inside of the rear gearbox at this point. See pictures below. It's a nice tight press fit, and the bearing protrudes less than a mm. Then the metal nut in the centre of the large gear can ride against this "thrust race". I wanted to stop any reasonable possibility of the gear rubbing on the inside of the gearbox so I also took the original black plastic JH rear axle bearing and sliced a 0.75mm "thrust washer" out of it with a razor saw (I held the bearing in a vice to do this and finished it off carefully holding it with fingers), and then filed it a little with the small flat file (out of the Tamiya 3 basic files set) so it was as flat as I could get it) and put it between the large gear and the bearing on the inside of the gearbox. The bearing here is 5mm ID not 4mm so it won't fit the axle snugly but doesn't matter as it's merely acting as a thrust race to stop friction and binding due to unwanted side motion of the rear axle.

I tried the same thing on the other side of the gearbox but when I tried pressing an 1150 bearing in it went in too easily and went down the rear axle "hole" too much. Then I realised that if I press in some more bearings I will eventually have one on the top, so I pressed in 2 more bearings, plastic this time, and with the 2nd plastic one I removed the inner "rim" that protrudes on this plastic bearing, using Tamiya's fine craft knife used very carefully. This is to allow the inner part of the metal bearing to be able to not bind against the plastic bearing when I added the final bearing. The final bearing was then added, a metal 1150 beearing, and I press fitted it in flush with anything I had to hand, in this case an 11/32" hex nut from a socket set (see pic's), the idea being that it presses the outer edge of the bearing not the inner part, which might well damage it. This other side of the gearbox however can only be assembled when the pinion has been fitted onto the replacement high performance motor, as pressing on both rear wheels prevents the gearbox from opening!

I cleaned up one rear wheel with White Spirit (wheel is ABS plastic, very hard) and then was ready to press fit it back on. However the act of reducing the rear axle in diameter by a gnat's wing (!) to allow it to pass through the rear axle ball race stops it's very end (4mm of it) being a nice press fit into the rear wheel nut on reassembly. However I found that it was a tight press fit if pressed on so that the axle protruded about 0.75mm from the nut! So I decided to remove a 1mm slice of material from the inner boss of this rear wheel with a razor saw, reducing the thickness of the rear wheel to 35.75mm. Then I cleaned up the face of the wheel nut with Autosol metal polish and cleaned the inside taper with white spirit and then put the wheel on, and pushed the nut into place, and then used a 3/32" rivetting tool (see pic's), the only thing I had to hand which was small enough a diameter not to damage the plastic of the wheel on the outside of the wheel nut, and large enough to fit over the wheel nut to ensure that it would only be hitting the wheel nut and not the central axle when I hit the end of the tool, as the centre of the tool 'tip' is hollow (domed actually).

I then used a medium sized hammer and gave the nut a sharp tap (not too hard by any means though) with the rivet tool whilst the other end of the axle was against the vice, the assembly being held simply by hand. This press fitted the wheel on, so that the rear small gear only turned very slightly when turning the wheel really very hard with the hand, whilst holding the wheel. There was a tiny amount of clearance (side play / end float) of the rear axle, and it was spinning nice and smoothly, so I left it at that and I think it will be quite satisfactory. I hope so anyway. If it ever gets slack I can always tap it out again with the hammer as before and take another 0.5mm slice off the rear wheel inner boss with razor saw / file which will make the wheel nut an even tighter press fit when reassembled.

I had been trying to work out how to get that rear wheel back on all week! These ideas only occurred to me last night!

Cheers,

Alistair G.

[dazaa 0]

This is brilliant stuff, please keep updating I love reading about how this is coming on. Just imagine it once its finished

[Live Steam Mad 17]

I just got around to temporarily fitting some electronics to the chassis to test my JH. First up I got the steering working nicely and took a video of it which is here ;-

...and now I have full steering lock available on both sides and the steering can be centred properly. The servo is many times more powerful than the stock servo. It's a Graupner / JR C507 . It's just a standard 1/10 servo, nothing special. For fitting it, see description and photo's above. Now I finally have proportional steering for the JH.

I have had to take out the battery box to allow space for the ESC and receiver. I am using an Acoms MK1 Transmitter as it is closest in looks to the original JH Tx , and it's much better since the JH Tx is quite a lot too small for adult hands. I am using an Acoms AR227FE Rx because the steering doesn't go mental when you switch off the Tx like happened on the Acoms AR201 when I tested it, and because it's an AM 27MHz Rx to be compatible with the Tx, and because it's got BEC in it so I don't need to run an extra Rx battery pack. I'm using a Tamiya TEU101BK ESC.

For the time being I am going to be only powering the stock motor and seeing how it runs on 6V (which seems to be the same voltage as Turbo mode) since I had some problems with the brushless idea. I just need to find a spare gearbox to do that with which has the motor still in it and working, I'll be soldering some bullet connectors to the motor to match to the ESC. I will probably be using Deans connectors instead of Tamiya connectors for the battery to ESC connection because the Tamiya connectors are I feel too big for the chassis (there's not much room available in there). Also I am going to be running with a 6V hump pack of NiMH AA cells. I want performance to be the same as the original stock JH first, so that I can see what the JH was like originally! The advantage will be 1) proportional throttle , and 2) it won't drop the motor to 1/2 voltage when it steers - when the original does that you can't steer at all on grass!!

Cheers,

Alistair G.

[Live Steam Mad 17]

I just tonight worked out a way of fitting the Acoms AR227FE Rx and the Tamiya 101 ESC and a 5 cell ( 6V ) AA sized battery pack into the chassis of the JH (see pic's below) ;-

As can be seen it's just about flush or nearly so with the top of the chassis so I'll be able to fit a 1/16 sized driver doll . Only problem is I have no idea which driver doll to use?

Cheers,

Alistair G.

[Live Steam Mad 17]

Finally I converted the Jet Hopper to full proportional steering and throttle !

I tried without success to get the gearbox on my rather used JH to be ballraced (I can't get the rear wheel nuts to fit onto the axles properly with their tapered fit) so instead I swapped the gearbox off my nicer condition JH (which just happens to have some scuffs under the gearbox only!) and mated it to the chassis of my heavily used JH that I did the proportional steering on.

The shock tops had to be swapped over but the pins on those, and the pin going through the gearbox which holds the gearbox onto the chassis, are interchangeable between the two JH's even though the JH which is heavily used had larger diameter suspension dampers compared to the dampers on my nicer one.

So now I have a complete working JH which works and is totally proportional. See video above!

Now I need to wire up a smaller battery pack for it LOL

Also just noticed front dampers are the bigger size of course and need to be swapped for the smaller ones LOL.

Control is rather good using the Tamiya TEU-101BK ESC. Brakes are good.

Cheers,

Alistair G.

[Live Steam Mad 17]

Just swapped over the front dampers so they match now ;-

Cheers,

Alistair G.

[supergreg 1]

Hey Jet Hopper addicts!

I wanted to let you know I found an easy way to get the press fit pinion off the motor. There's a tool available from Modelcraft that does the trick. it's this one:

Here's how it works:

The pinion comes off without damaging the motor or the pinion. The whole process takes zero brute force and is finished within a minute. The tool is available from conrad.de here in germany, but I'm sure there's something similar from other manufacturers all over the world. here's the product link: http://www.conrad.de/ce/de/product/206407/

cheers

Kai

[supergreg 1]

I just found out there's also a UK based Conrad online store: http://shop.conrad-uk.com/hobbies/modellin..._1/206407.html#

[Live Steam Mad 17]

I wanted to let you know I found an easy way to get the press fit pinion off the motor. There's a tool available from Modelcraft that does the trick.

Kai

Great stuff Kai, good work, this is great info for when I try brushless power in my JH.

That tool is commonly called a "Puller" by the way.

Well my battery pack for my own Jet Hopper finally arrived today! A custom pack of 5 AA cells, in 3+2 hump configuration, 2500mAh, 6V, NiMH, part number PN-2505H, from www.onlybatterypacks.com , I ordered it with a Tamiya Female connector on the end for connecting to standard 1/10 buggy style battery chargers and ESC's etc. I had previously mocked up a pack of old cells wrapped with cellotape and it fit nicely into the JH battery compartment (with the battery tabs / springs removed) so here's hoping it'll work.

Here's a picture of the pack ;-

Cheers,

Alistair G.

[loco_oso 108]

Thank you so much for posting this info!!! Especially about the rear wheels and the motor voltage! I've been trying to figure out the rear axle for months!!!

Obviously these ^ ramblings don't make sense now, but maybe in the future they will....

Thanks again!!!

(and thanks to TA-Mark too for helping you with some of the info )

[Jason1145 3986]

Wow what a thread! By that I mean there's too much to take in!

So I just bought a used Jet Hopper.... love this buggy from back in the day, however mine goes forward and backward.... but no steering.... It has the original hand controller.

I bought it knowing this... hoping I could just swap in a new servo...... well I had no idea of the make up of the buggy and that it is all soldered to a big PCB board... so not as easy as I hoped.

So my next idea.... how easy to remove the PCB and replace it with a modern esc and radio... and somewhow to fix the servo or replace it?

 

[supergreg 1]

Hi Jason,

you might want to check out my showroom entry: 

[Jason1145 3986]

On ‎15‎/‎11‎/‎2016 at 6:44 PM, supergreg said:

Hi Jason,

you might want to check out my showroom entry: 

Greg!

Sweeeeeeet Jet Hopper you have... I think I'd like to get mine to a similar spec with all new electronics!

 

 

[Hibernaculum 933]

On 15/11/2016 at 3:45 AM, Jason1145 said:

Wow what a thread! By that I mean there's too much to take in!

So I just bought a used Jet Hopper.... love this buggy from back in the day, however mine goes forward and backward.... but no steering.... It has the original hand controller.

I bought it knowing this... hoping I could just swap in a new servo...... well I had no idea of the make up of the buggy and that it is all soldered to a big PCB board... so not as easy as I hoped.

So my next idea.... how easy to remove the PCB and replace it with a modern esc and radio... and somewhow to fix the servo or replace it?

 

Before you go ripping the guts out to get the steering working, consider 3 things.

1) Taiyo Jet Hoppers are easy to fix. Disassemble the transmitter, and clean the contact points (both track and points) carefully. They came with grease on them, and this simply builds up with gunk over the years. Clean them with the tip of a rag, and a dab of soapy water. After drying, shine them up carefully with the corner of a very fine piece of sand paper. In 99% of cases, this will make the car function like new.

2) A NIB Taiyo Jet Hopper is now often worth more than a NIB vintage Tamiya Frog.

3) Modifying any valuable vintage toy-grade R/C, will reduce it's value.

Taiyo Jet Hoppers are highly collectible, including in used (but good) condition. I have been collecting and restoring them for many years, and I have sold quite a few. If you are happy to modify for fun, and never sell, then go ahead and modify. However, if you would like to preserve the value and originality of the car, do not modify it. Other collectors will only want original.

H.

 

[Jason1145 3986]

7 hours ago, Hibernaculum said:

 

Before you go ripping the guts out to get the steering working, consider 3 things.

1) Taiyo Jet Hoppers are easy to fix. Disassemble the transmitter, and clean the contact points (both track and points) carefully. They came with grease on them, and this simply builds up with gunk over the years. Clean them with the tip of a rag, and a dab of soapy water. After drying, shine them up carefully with the corner of a very fine piece of sand paper. In 99% of cases, this will make the car function like new.

2) A NIB Taiyo Jet Hopper is now often worth more than a NIB vintage Tamiya Frog.

3) Modifying any valuable vintage toy-grade R/C, will reduce it's value.

Taiyo Jet Hoppers are highly collectible, including in used (but good) condition. I have been collecting and restoring them for many years, and I have sold quite a few. If you are happy to modify for fun, and never sell, then go ahead and modify. However, if you would like to preserve the value and originality of the car, do not modify it. Other collectors will only want original.

H.

 

Thanks very much pal, will give this a go, any chance of a picture for this exact spot that needs cleaning up that would be very helpful indeed?