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Cox Engine of The Month
September-2019
Levent Suberk's

CEF Magazine cover featuring the Ex Model Engines Harpy Eagle .049



PAST WINNERS
CEF Traveling Engine

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Gallery


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Jerobee Corvette

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Post  OVERLORD on Thu Sep 24, 2015 6:41 pm

Thanks Roddie,

I think you are mixing up the throttle control rod and the brake rod. The rod for the throttle is straight. The rod for the brake has a strange shape and hinges on the chassis.

Jerobee Corvette - Page 2 Imgp6127

The Greenwood Corvette is a little different from the Comando (Mc Laren Mk8) and the Bandero (Porsche). It has the external tank, a brake and wider tyres. It was delivered standard with the heat sink and a lexan body, much lighter than the ABS one. Bolow a picture of the original box:

Jerobee Corvette - Page 2 Getuse10

I took the head of and I could see only 1 transfer port. Although the Jerobee blog says that there are 2:

"Greenwood Corvette.
The Corvette was a mid range kit.
On the box it says " Not recommended for beginners".

The Corvette had a twin intake ports in the cylinder and a large external tank. Wider chromed wheels with foam tires was standard equipment.
The body was made out of Lexan, not the hard Cycolac plastic as the McLaren and the Challenger had.
This was the fastest Jerobee with Cox Babe Bee and pull start, only the Cox Tee Dee version was faster."


http://jerobee.blogspot.fr/

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Post  roddie on Thu Sep 24, 2015 7:39 pm

OVERLORD wrote:Thanks Roddie,

I think you are mixing up the throttle control rod and the brake rod. The rod for the throttle is straight. The rod for the brake has a strange shape and hinges on the chassis.

Jerobee Corvette - Page 2 Imgp6127

I took the head of and I could see only 1 transfer port. Although the Jerobee blog says that there are 2:

Lieven

Yes, I see now. Still.. even straight, it's a novel way of converting to a sweeping-motion of the rod to rotate the clip/barrel. The band-brake's pushrod is baffling me. Is there a 2nd servo-horn beneath the throttle horn? I can see how it would work.. but can't see it connected anywhere. It appears that clockwise servo movement opens the throttle and releases tension on the band using the same servo.
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Post  OVERLORD on Fri Sep 25, 2015 6:45 am

Rodie, The hook of the brake rod is out of the hole and sits just below the servo horn. It just catches in the hole but need refixing.

This picture of another car shows the set up. Look at the small fan to cool the engine!

Jerobee Corvette - Page 2 Chassi10

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Jerobee Corvette - Page 2 Empty My Jerobee is fantastic

Post  OVERLORD on Tue Dec 29, 2015 7:13 pm

As it's a calm period at work, I decided to give my Jerobee Corvette a clean. With a cotton bud and alcohol, I cleaned the chassis and all corners. I removed the engine for further cleaning. The tube to which connects the fuel pipe from the tank is the standard Cox pick up tube with the spring.

Jerobee Corvette - Page 2 Imgp7514

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I removed the heat sink and head. The cylinder has 1 bypass port. The flyweights, clutch shaft and bell house bearing were in good condition. The hexagonal rear axle turns in plastic bearings that you have to pry open for fitting around the shaft. There is a little play on the rear axle gear. No play was found on the rear wheels. They are secured to the shaft with C clips. The brake band is a tie wrap from an electrician.

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After assembling everything back together, I tested the servos. The steering servo was OK but the throttle servo was totally dead without giving any noise at all. Both servos are glued with époxy to the chassis. I tried to cut around the bottom edge of the servo with a knife to remove it without success. Not wanting to damage the chassis, I left it on there and decided to cut off the plastic servo shaft and to use the servo as a bracket for the replacement servo. This new servo is a lot smaller and fixed with a tie wrap to the original one.  This meant I had to make a new throttle shaft and extend the brake lever. Before, the brake lever was also fixed to the servo wheel. I decided to just make a hook: when the servo is turned the other way, it pulls the hook and brakes will be applied without significantly change idle.

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IDLE

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FULL THROTTLE

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BRAKING

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I just filled the tank with some fuel and will let it sit during the night to loosen residues. To be continued.

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Post  cox24711 on Tue Dec 29, 2015 9:07 pm

wow nice! vettie i would love to have one of those Very Happy
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Post  rsv1cox on Tue Dec 29, 2015 11:16 pm

Regarding the "Postwoman" headline.

I always tip the local mail carriers (two ladies) at Christmas. This Christmas I used a priority mail label on the envelope and typed "To the worlds's best mail carriers" on it. I'm still getting "Thank you" cards from these ladies that deliver the mail in all kinds of weather.

These are "contract" mail carriers. In our very rural post offfice there is just one government postal employee so there is no conflict of interest in them accepting a gift.
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Post  roddie on Wed Dec 30, 2015 2:52 am

I can't get over what a mechanical marvel this model is.. and it's luckily in the hands of a fine hobbyist!
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Post  getback on Wed Dec 30, 2015 3:09 pm

Looks to be cleaning up good for you , that will put some pep in you step . looking good Lieven , getback Small Cox Logo
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Post  1/2A Nut on Wed Dec 30, 2015 3:13 pm

Lucky duck Overlord, what a mechanical marvel in deed and in such great shape!
Awesome find and now in the safety of a skilled hobbyist that will take care of it and bring it back for all to see and enjoy. Small Cox Logo Small Cox Logo Small Cox Logo

Cheers!
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Post  TDbandit on Wed Dec 30, 2015 5:58 pm

Nice jerobe! I've seen one of those years ago. BTW you know that you can get a gear set for that S3001 servo right?
Part number is FUTM3400 same gear set as the futaba S148 and the servo is still in production bope this helps! (Bandit)
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Post  OVERLORD on Wed Dec 30, 2015 6:59 pm

Thanks guys, you're all very kind.

Thanks Bandit for the info. The reason why the servo stayed on the chassis as it was, is the fact that I can't get it off in a way that wouldn't damage the chassis. And because I can't remove the servo, I can't get to the bolts underneath to take it apart. The servo doesn't have a gear problem, I think it's an electronic failure or maybe just a loose wire on the circuit board!!

I had a look at the steering today. Not exactly Akkerman!!

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Jerobee Corvette - Page 2 Imgp7611

To get tru rolling of the front wheels in a curve, the inner wheel should be more at an angle than the outer wheel. The pics above show the opposite. It's all in the linkages and connections to the steering arms. On original factory pictures, the steering rod is fixed between the servo and the most forward hole of the steering arm. On my model, both steering linkages are fixed to the rear hole in the steering arms. This makes a big difference. I uncoupled the ball joints at each side and put the servo in both left and right end positions. I then put each end of the steering linkages on the forward hole of the steering arm and that gives a better result:

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Jerobee Corvette - Page 2 Imgp7613

Both ball joints will be moved forward and the I'll adjust the linkages to get a slight toe in for stable driving.

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Post  OVERLORD on Sun Jan 03, 2016 9:04 am

As said above, I removed the ball joints from the steering arms to move them forward and obtain a better wheel position while steering. The left one screwed out all right, but when I was half way on the right right ball joint... oh malheur!!!!... a part of the steering arm fell off. It seems to have been broken already before just in way of the enlarged hole for the ball joint. I discovered some glue on the steering arm.

Jerobee Corvette - Page 2 Imgp7614

I made 2 new steering arms from a sheet of ABS to glue on the original ones for repair and to reinforce.

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I stuck both steering arms on with époxy. It is still drying until tomorrow.

There was plenty of rubbish in the fuel tank so I removed the plug. The rubber gasket is "slightly dated". I'm thinking of replacing the complete tank.

Jerobee Corvette - Page 2 Imgp7619
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Post  Oldenginerod on Sun Jan 03, 2016 10:08 am

Lieven.  A picture that you posted earler (which I have attached) shows a different steering set-up with a rigid tie-rod joining the steering arms at the outer hole and the control rod (drag-link) coming from the servo to the inner hole on one arm.  This would maintain a better geometry than the set-up you are using.  The trouble with your system is that as the servo rotates the relationship between the two steering arms changes, effectivily altering the toe-in as the rods raise and lower due to the rotation of the servo.

I'll try to explain what I mean.  The two ball joints attached to your servo appear to be about 20mm apart when set straight ahead.  As the servo rotates, the ball joints move together in the horizontal plane.  At 90° of rotation, the gap is completely gone in a horizontal sense.  This is reducing the toe-in by 20mm at "full lock".  

I hope I explained it ok, but I think you need to change the design to what is pictured here.
Jerobee Corvette - Page 2 Chassi10

Rod.
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Post  OVERLORD on Sun Jan 03, 2016 10:37 am

Thanks Rod, yes I know; that's the original Jerobe set up with a proper track rod between both wheels. On some pictures, the track rod is connected to the forward holes and on others, to the rear ones. On my model, a previous owner mounted the servo saver and the more recent setup with 2 linkages. I just connected the linkages and did a test but it's still not the way it should be. I'll try to make a a proper track rod with only 1 linkage from the servo saver to the left steering arm.
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Post  Oldenginerod on Sun Jan 03, 2016 12:20 pm

Swapping the track rod from the front holes to the rear will not seriously alter the steering geometry, but will alter the ratio significantly between the servo and the wheels. It depends on how sensitive you want the steering. There will probably be a little bit of difference to the "toe-out on turns" as we call it, if you use the different holes, but it would be negligible.

I have had to try to rectify a couple of vehicles (full size) which had steering geometry faults and I can tell you for sure, you will nevr make the system that you have work correctly if you continue to allow the tie-rods to have up & down movement at the servo end due to servo rotation. Some type of bellcrank arrangement may help, but I would definitely use a common track rod to join the two sides to each other.
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Post  roddie on Sun Jan 03, 2016 1:41 pm

Just throwing this out there... how about installing a linear servo and/or a small mixing tray.. if you could build one to fit? Is the steering servo glued to the chassis too?

Here's a small one..

Jerobee Corvette - Page 2 Linear10

buy it here

or this.. which fits the Futaba S3003 servo.

Jerobee Corvette - Page 2 Linear11

buy it here
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Post  OVERLORD on Sun Jan 03, 2016 4:46 pm

Yes this servo is also glued onto the chassis. That's a nice little servo. Just as in the early days of RC but much smaller.

I made a track rod and a new linkage from the servo to the left steering arm.

Jerobee Corvette - Page 2 Imgp7620
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Post  roddie on Sun Jan 03, 2016 5:49 pm

Nice job Lieven! The fuel tank looks like it could be a Sullivan #435 1oz./29.5cc slant-type.

Jerobee Corvette - Page 2 Dsc03010

You can obtain a stopper kit #S482 which is for glow-fuel.

Jerobee Corvette - Page 2 S482-s10

This might be nice too.. #S469

Jerobee Corvette - Page 2 S469_m10
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Post  pkrankow on Sun Jan 03, 2016 6:11 pm

Save the old clunk! It looks like the tapered bullet/cone shaped clunk. You might want to reuse it as it will drain the tank a little more effectively.

All the same clunks can be cleaned and reused with no worries.

Phil
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Post  OVERLORD on Sun Jan 03, 2016 7:14 pm

That's the tank. I'll buy a complete new one. They are sold by Scientific France. I'll save the tapered clunk.
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Jerobee Corvette - Page 2 Empty They are also sold by a Chinese company

Post  happydad on Sun Jan 03, 2016 9:26 pm

OVERLORD wrote:That's the tank. I'll buy a complete new one. They are sold by Scientific France. I'll save the tapered clunk.

The small tanks are also sold by a Chinese company, i will repost later from my PC, and include everything including the clunk. They were taking offers and i picked up a couple for less than $4.00 each shipped to U. S. 60cc and 360cc tanks.

edited 1-3-2016 2:23p.m. PST - to add link to tank.

sorry can't seem to post a pic of the tank

Jerobee Corvette - Page 2 90ccta10
generic picture for tank


link:
http://www.ebay.com/itm/111641213018?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT


P.s. The linear servo could never stand up to the stress of a crash without a servo saver of some sort. It may be hard to implement with the linear type servo.

Happydad RC Plane Futaba Radio Jeep


Last edited by happydad on Tue Jan 05, 2016 12:44 am; edited 2 times in total (Reason for editing : to add link to tank)
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Post  OVERLORD on Mon Jan 04, 2016 7:51 pm

Thanks for the link!!
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Post  OVERLORD on Tue Jan 05, 2016 2:43 pm

With the body on

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Jerobee Corvette - Page 2 Imgp7622
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Post  getback on Tue Jan 05, 2016 3:22 pm

Hoot Hoot man that's NICE ! she is going to bee Sharpe when done , I like that body style lots of curves . Are you waiting on parts now ? what radio are you going to use ? getback Smoking
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Post  OVERLORD on Tue Jan 05, 2016 5:01 pm

Thanks Eric, In the first place, I'm wating for some descent weather. Yes, I need to buy a ne tank but I fitted another temporary tank for the first trials. My radio? I bought one this year, not a super expensive one: a T2M Pilot 6G , 6 channel 2,4 Ghz.

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I just had a good look. It says "T2M Racing Products"!!! You can imagine how fast that car will go with that radio lol!
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